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Working with WebSockets in WCF 4.5

clock November 24, 2012 07:06 by author Administrator

Web Services have one great virtue: they're completely interoperable. They also have one great failing: in order to be interoperable, Web Services use a set of technologies that are guaranteed to give you, at best, adequate performance. Fortunately, WCF 4.5 has a solution: support for WebSockets.

Ever since Web Services appeared, developers have been trying to make them run faster. REST and JSON can be seen as a way of speeding things up by reducing the overhead in the messaging format used by Web Services. However, even with REST and JSON you're still moving and parsing text, which is the bulkiest and slowest data transfer mechanism; you'd get better performance if you could move binary data around. And REST and JSON don't tackle another reason for why Web Services give poor performance: HTTP, the network protocol used by Web Services. There are slower protocols than HTTP around, but no one is using them.

But performance isn't the only issue that using HTTP creates: HTTP in Web Services is tied to a request/response cycle. The reason Ajax applications make all their requests asynchronously is because if you call a service that takes a long time to complete, your request has to wait for that response before you can get your result.

On top of that, if your service has something else to tell your client after that initial response (an ongoing set of updates, for instance), then either your client has to make repeated polling calls to the service to get the result (another performance burden) or, in a non-Ajax application, you have to set up a complementary Web Service that the service can call with the updates.

A far better arrangement would be for the client to submit its request in a "fire and forget" kind of arrangement and then for the service to call back to the client when it has the data (and keep calling back if there are updates to send).

WebSockets addresses all of those issues, while still being an industry standard and therefore interoperable (confusions in vendor's implementations of the standard may interfere). In fact, your browser probably already supports WebSockets.

For most processing, WebSockets uses TCP to communicate, giving you the benefit of a faster protocol. WebSockets also supports sending both binary (for speed) and text (for interoperability). But in many ways, the best part of WebSockets is that it supports two-way communication: The client can call the service just to open communication; and after that, the service can call the client whenever it has information to share. And WCF 4.5 provides support for WebSockets.

So in the next few columns, I'm going to look at WebSockets in WCF 4.5. I'll look at the two ways you can implement WebSockets (one complicated and flexible, one simpler and less flexible) and create client a JavaScript client. Along the way I'll also discuss some of the issues you should consider in creating a WebSocket application.

Configuring the Server

One warning: You may not be able to use the code in this series, yet. As I write this (April 2012), WebSockets is only supported on Windows 8 (I worked on the 64-bit beta ISO for Windows 8 Server); even then, you'll need to configure Windows 8 to support WebSockets.

To configure Windows 8, in Server Manager, from the Manage menu, run the Add Server Roles and Features wizard. In the Wizard, you'll need to add the Web Server (IIS) role. After that, under Features, select ASP.NET 4.5 (if it isn't already selected) and, under Web Services, select HTTP Activation. Finally, under Web Services (IIS)/Role Services, select WebSockets. After  finishinb the Wizard, select Local Server and set IIS Enhanced Security Configuration to off.

To work with WCF 4.5, you'll need Visual Studio 11 (again, in beta, as I write this). The first time you run it, Visual Studio 11 will probably offer to download an update; if so, take the update (I took the update and I won't guarantee that the following code will work without it).

Second warning: This may be a frustrating set of columns if you're reading them as soon as I post them. I've got a fair amount of ground to cover so, in this column, I'll only be setting up to write the code that a WebSocket service requires. But hang tough; the next column will have the code and subsequent columns will show you how to build the clients and provide an alternative way to build a WebSocket service.

Building the Service

I did my testing with a WCF Service Application Project. To take advantage of IIS's support for WebSockets that I'd just finished configuring, I went to the Web tab of my Project Properties and unchecked the Use IIS Express option so that I was testing with the "real" IIS.

Once you've set up your server and project, the first step in creating your WebSocket service is to define two interfaces: one with a single method that accepts requests from clients and another interface with a single method to send results.

For the first interface, I'll define a method that accepts an Order Id (I call the method OrderStatusById method and the interface IRequestOrderStatusUpdates). In the ServiceContract attribute on the interface that accepts requests, you need to use the attribute's CallbackContract to specify the second interface (the one with the method used to send data back to the client is ISendOrderStatus in this example). The method must accept a Message as its only input parameter and the method's OperationContract attribute must set its IsOneWay property to True and its Action property to an asterisk.

The result for my Order status example looks like this:

<ServiceContract(CallbackContract:=GetType(ISendOrderStatus))>
Public Interface IRequestOrderStatusUpdate

  <OperationContract(IsOneWay:=True, Action:="*")>
  Sub OrderStatusByID(OrderStatusMessage  As Channels.Message)

End Interface

The definition for the return method is similar, except that you don't need any special specifications for the ServiceContract attribute. I've called my method SendOrderStatus:

<ServiceContract()>
Public Interface ISendOrderStatus

  <OperationContract(IsOneWay:=True, Action:="*")>
  Sub SendOrderStatus(OrderStatusMessage  As Channels.Message)

End Interface

At this point you're ready to write the code for these methods, which I'll look at in my next column (the column after that will look at building a client).



SOLVED: "Operation could destabilize the runtime" - ASP.NET 4.5 Hosting

clock October 18, 2012 07:29 by author Administrator

We like to discuss an issue, which normally happens to ASP.NET 4.5 website on Windows Server 2008. We did not spot this issue on Windows Server 2008/Windows Server 2012 and we believe that this issue happens to ASP.NET 4.5 Framework on Windows Server 2008 only. Please note that ASP.NET 4.5 is not supported on Windows Server 2003 or lower.

When you are using Windows Server 2008 and you do make an upgrade of ASP.NET framework to ASP.NET 4.5, your site can stop working with the error message: “Operation could destabilize the runtime

The following is the detail of the error message:

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.  

Exception Details: System.Security.VerificationException: Operation could destabilize the runtime.

To resolve this issue, please kindly make sure the following items are set on your IIS:

1. Please make sure that the ISAPI Filters of your website is set to Revert to Inherited
2. Please make sure that the application pool is running under ASP.NET 4.0 (ASP.NET 4.5 and ASP.NET 4.0 will share the same application pool settings)
3. Please make sure the “Enable 32-bits mode” is set to False

If you are looking to host your
ASP.NET 4.5 website on Windows Server 2012, please have a look at asphostcentral.com

Hope this helps!

 



VS 2012 Hosting :: ASP.NET Web Forms 4.5 new features in Visual Studio 2012

clock September 25, 2012 08:13 by author Administrator

This post discusses about ASP.NET Web Forms 4.5 features, Web Forms in 4.5 allows you to build dynamic web sites quickly and easily. Web Forms generates much cleaner code on client-side with Unobtrusive Validation in this version. You can also build data-centric applications easily with data-binding features.

If you like to host your ASP.NET Web Forms 4.5, you can have a look at
asphostcentral.com

Typical Web Form which contains more fields and validation controls can generate more code on client-side. When you run this typical form in browser then you can see the page size as below



The reason for this size is because client-side validation is enabled. If you change Unobtrusive validation mode in page load to web forms then you can see the difference.



Now re-compile your application and run the page the result is as shown below, Now page size is much smaller than before



Strongly typed Data Controls

Take a typical Search Form which shows the results in list view. Inside list view you have item template which is having multiple calls to the EVAL expression as shown below



The above method is the standard way of doing data-binding in web forms. You optimize the above using strongly typed data controls.

You can set the Item Type property of List View to the type that you actually data-binding to as shown below



Now you can member variables in place of Eval expressions, member variables are now typed and you will get an Intel license on item class



Model Binding

You may be familiar with Model Binding in ASP.NET MVC, The typical code which you might write in web forms to bind the results in web forms as below



The above code talking to the data base by building a query which does a case insensitive search then it coverts into list binds the results to list view. Let us re-write the above code using Model-Binding



Now there is no page load and click-handler, The above code is not directly interacting with the page. You can populate the formTerm and qsTerm variables using attributes Control and QueryString in model-binding.

The return result of GetResults method is IQueryable. Because the result is of type IQueryable the control has the ability to modify this before it is rendering it to the page. You can use this in sorting and paging. You can specify the same in markup.

Advantage of using Model Binding


As the code is not directly interacting with the page, you can fairly easily unit test the method or even move it to the completely different class.

Support for OpenID in OAuth Logins



The AuthConfig.cs file is standard in all new projects that created in ASP.NET 4.5 in Visual Studio 2012. You can see there are number of external services code is commented out and it is ready to use by putting your custom application credentials.

Now you can use external services to login to the application.

These are the features which you can try out in Visual Studio 2012.



ASP.NET 4.5 Hosting: Filtering using Model Binding in ASP.NET Web Forms

clock September 17, 2012 08:15 by author Administrator

In ASP.NET 4.5, we are provided with the ‘System.Web.ModelBinding’ namespace. This namespace contains value provider classes e.g. ControlAttribute, QueryStringAttribute etc. These classed are inherited from ‘ValueProviderSourceAttribute’. This base class is used to define method parameters to specify source of values for model binding. The means that the parameter passed to the method specifies what value is to be taken for filtering records and what is the source of the value. This source may be Control, QueryString etc.

Step 1: Open Visual Studio 2011 Developer Preview and create a ASP.NET Web Application targeted to .NET 4.5. Name it as ‘ASPNET45_ModelBinding’. To this project, add two new Folders with the name ‘Model’ and ‘Employee’.

Step 2: In the model folder, add a new ADO.NET Entity Framework and  name it as ‘CompanyEDMX.edmx’. This EMD makes use of SQL Server 2008 and a Company Database in it.

The Schema of the Tables in the Company Database is as below:



Department - DeptNo (int) Primary Key, Dname (varchar(50)),Location (varchar(50)).
Employee - EmpNo (int) Primary Key, EmpName (varchar(50)),Salary (int), DeptNo(int) Foreign Key.

After the Wizard completes, the ADO.NET EF model will be as shown below:

Department Employee Table

Step 3: In the Employee folder, add a web form (with master page). Name it as ‘Employees.aspx’. Open the Employee.aspx in Source view and add DropDownList and GridView on it. Set properties of these controls as shown below:



The Entire Page Design markup will be as shown below:



Step 4: Open the Employees.aspx.cs and add the following code in it:

The important part in the code shown above is the ‘GetEmployees()’ method, which accepts a nullable parameter - DeptNo. This is defined using the [Control] attributes. This attribute class defines the constructor which accepts the ID of the control from which the source value is accepted. In the above case, the source control is the DropDownList with ID as ‘ddlDeptName’. Here the ‘GetEmployees()’ method accepts the DeptNo and based upon this value, the related Employees are read from the Employees collection.

Another important portion of the GridView code shown above is that the AllowPaging property is set to true. In the earlier versions of ASP.NET, it was necessary of a Developer to write the code for pagination in similar scenarioes. But in this case, the ‘GetEmployees()’ method returns ‘IQueryable’. Now  when the end-user changes the page-index of the GridView, the query is automatically updated and the next page records are displayed.

Step 5: Run the Employees.aspx and select the Dname from the DropDownList.

Conclusion: Using ASP.NET 4.5 Model Binding Value providers, communication between controls can be made possible by using less code.



ASP.NET 4.5 Hosting :: Working with Asynchronous Operations in ASP.NET 4.5 Web Forms

clock September 4, 2012 06:28 by author Administrator

 

Introduction

Asynchronously running code can improve the overall performance and responsiveness of your web application. In ASP.NET 4.5 web forms applications you can register asynchronous methods with the page framework. The ASP.NET page framework and .NET 4.5 asynchronous programming supports then executes the operations in asynchronous fashion. This article shows how this can be done.

NOTE: This article discusses how asynchronous operations can be used in ASP.NET web forms applications. Read Working with Asynchronous Operations in ASP.NET MVC to learn how asynchronous operations can be programed in ASP.NET MVC applications.

If you are looking to host your ASP.NET 4.5 website, you can check out ASPHostCentral.com

 


Example Scenario

Consider that you have a web application that needs to call two ASP.NET Web API services namely Customer and Product. These services return Customer and Product data from the Northwind database respectively. Now, assume that each of these services take 5 seconds to complete the data retrieval operation. If you use synchronous mode for calling these services then the total time taken will be 10 seconds. Because the execution will happen sequentially - first Customer service will complete and then Product service will complete.

On the other hand if you invoke these services in asynchronous fashion, the service operations won't block the caller thread. The Customer service will be invoked and control will be immediately returned to the caller. The caller thread will then proceed to invoke the Product service. So, two operations will be invoked in parallel. In this case the total time taken for completing both of the operations will be the time taken by the longest of the operations (5 seconds in this case).

Async, Await, Task and RegisterAsyncTask

Before developing web forms applications that execute asynchronous operations you need to understand a few basic terms involved in the process.

A task is an operation that is to be executed in asynchronous fashion. Such an operation is programmatically represented by the Task class from System.Threading.Tasks namespace.

When an asynchronous operation begins, the caller thread can continue its work further. However, the caller thread must wait at some point of time for the asynchronous operation to complete. The await keyword invokes an asynchronous operation and waits for it to complete.

The async modifier is applied to a method that is to be invoked asynchronously. Such an asynchronous method typically returns a Task object and has at least one await call inside it.

Just to understand how async, await and task are used at code level, consider the following piece of code:

public async Task<MyObject> MyMethodAsync()
{
  MyObject data = await service.GetDataAsync();
  //other operations on data go here
  return data;
}

Here, method MyMethodAsync() is marked with async modifier. By convention, asynchronous method names end with "Async". The MyMethodAsync() returns MyObject wrapped inside a Task instance. Inside the method a remote service is invoked using GetDataAsync(). Since MyMethodAsync() needs to return data retrieved from the service, the await keyword is used to wait till the GetDataAsync() method returns. Once GetDataAsync() returns the execution is resumed and further code is executed. The data is finally returned to the caller.

NOTE:
For a detailed understanding of async, await and Task refer to MSDN dicumentation. Here, these terms are discussed only for giving a basic understanding of the respective keywords.

ASP.NET page framework provides a method - RegisterAsyncTask() - that registers an asynchronous task with the page framework. Tasks registered using the RegisterAsyncTask() method are invoked immediately after the PreRender event. The RegisterAsyncTask() method takes a parameter of type PageAsyncTask. The PageAsyncTask object wraps the information about an asynchronous task registered with a page. The following piece of code shows how they are used:

protected void Page_Load(object sender, EventArgs e)
{
   PageAsyncTask task = new PageAsyncTask(MyMethod);
   RegisterAsyncTask(task);
}

Asynchronous Solution

Now that you are familiar with the basic concepts involved in utilizing asynchronous operations in a web forms application, let's create a sample application that puts this knowledge to use.

Begin by creating two projects - an empty web forms application and an ASP.NET MVC4 Web API application.

Add an Entity Framework Data Model for the Customers and Products tables of the Northwind database. Place the EF data model inside the Models folder.



Add an Entity Framework Data Model for the Customers and Products tables

Add two ApiController classes to the Web API project and name them as CustomerController and ProductController.



Add two ApiController classes

Then add Get() methods to both the ApiController classes as shown below:

public class CustomerController : ApiController
{
    public IEnumerable<Customer> Get()
    {
        Northwind db = new Northwind();
        var data = from item in db.Customers
                    select item;
        System.Threading.Thread.Sleep(5000);
        return data;
    }
}

public class ProductController : ApiController
{
    public IEnumerable<Product> Get()
    {
        Northwind db = new Northwind();
        var data = from item in db.Products
                    select item;
        System.Threading.Thread.Sleep(5000);
        return data;
    }
}

The Get() method of the CustomerController class selects all the Customer records from the Customers table whereas the Get() method of the ProductController class selects all the Product records. For the sake of testing, a delay of 5 seconds is introduced in each Get() method. The Get() methods return an IEnumerable collection of Customer and Product objects respectively.

Now, go to the web forms project and open the code behind file of the default web form. Here, you will write a couple of private methods that invoke the Web API developed previously. These methods are shown below:

public async Task<List<Customer>> InvokeCustomerService()
{
    using (HttpClient client = new HttpClient())
    {
        HttpResponseMessage response = await client.GetAsync("http://localhost:49187/api/customer");
        string json= (await response.Content.ReadAsStringAsync());
        List<Customer> data = JsonConvert.DeserializeObject<List<Customer>>(json);
        return data;
    }
}

public async Task<List<Product>> InvokeProductService()
{
    using (HttpClient client = new HttpClient())
    {
        HttpResponseMessage response = await client.GetAsync("http://localhost:49187/api/product");
        string json = (await response.Content.ReadAsStringAsync());
        List<Product> data = JsonConvert.DeserializeObject<List<Product>>(json);
        return data;
    }
}

The InvokeCustomerService() method invokes the Customer Web API whereas InvokeProductService() method invokes Product Web API. Both the methods essentially use an HttpClient to get data from the respective Web API. Notice that both the methods have async modifier and return a Task instance that wraps the actual return type (List<Customer> and List<Product> respectively). The GetAsync() method of the HttpClient object is an asynchronous method. Call to the GetAsync() is marked using the await keyword so that further statements are executed only when GetAsync() returns. The GetAsync() method accepts a URL of the respective Web API. Make sure to change the port number as per your development setup. The GetAsync() method returns an HttpResponseMessage object. The actual data is then retrieved using ReadAsStringAsync() method of the Content property. The ReadAsStringAsync() will return data as a JSON string. This JSON data is converted into a .NET generic List using DeserializeObject() method of the JsonConvert class. The JsonConvert class comes from the Json.NET open source componenet. You can download Json.NET here.

The InvokeCustomerService() and InvokeProductService() methods are called inside another private method GetDataFromServicesAsync() as shown below:

private async Task GetDataFromServicesAsync()
{
    Stopwatch stopWatch = new Stopwatch();
    stopWatch.Start();
    var task1 = InvokeCustomerService();
    var task2 = InvokeProductService();
    await Task.WhenAll(task1, task2);

    List<Customer> data1 = task1.Result;
    List<Product> data2 = task2.Result;           

    stopWatch.Stop();
    Label2.Text = string.Format("<h2>Retrieved {0} customers and {1} products in {2} seconds.</h2>",                                  data1.Count, data2.Count, stopWatch.Elapsed.TotalSeconds);
}

As shown above, GetDataFromServicesAsync() is also marked as async and returns a Task instance. Inside, a StopWatch class from System.Diagnostics namespace is used to find the time taken by both of the operations to complete. InvokeCustomerService() and InvokeProductService() methods are then called. The returned Task instance is stored in task1 and task2 variables respectively. The WhenAll() method of Task class creates another Task that completes when all the specified tasks are complete. In this case it creates a Task that completes after complition of task1 and task2. Actual data returned by the respective Web API is retrieved using the Result property of the respective Task objects. The time taken to complete the operation is measured by the StopWatch and is displayed in a Label.

The next step is to register GetDataFromServicesAsync() with the page framework. This is done using the RegisterAsyncTask() method as shown below:

protected void Page_Load(object sender, EventArgs e)
{
    RegisterAsyncTask(new PageAsyncTask(GetDataFromServicesAsync));
}

As you can see, Page_Load event handler registers an asynchronous task using RegisterAsyncTask() method. The RegisterAsyncTask() method accepts an instance of PageAsyncTask. The PageAsyncTask instance in turn wraps the GetDataFromServicesAsync() method created earlier.

The final step is to set Async attribute of the @Page directive to true:

<%@ Page Async="true" Language="C#" CodeBehind="WebForm1.aspx.cs" ... %>

The Aync attribute of the @Page directive indicates that this web form will be executed in asynchronous fashion. Web forms that use RegisterAsyncTask() method must set the Async attribute to true, otherwise an exception is raised at runtime.

This completes the application and you can test it by running the web forms application. The following figure shows a sample run of the web form:

 
A sample run of the web form

Though the code doesn't show the synchronous execution of the Web API operations, for the sake of better understanding the above figure shows time taken for synchronous as well as asynchronous execution. Recollect that both the Get() methods sleep for 5 seconds and hence the synchronous execution takes approximately 10 seconds. However, the asynchronous execution takes approximately 5 seconds. As you can see the asynchronous operation improves the overall performance of the application.

Summary

Using async and await keywords you can create operations that run asynchronously. Such asynchronous tasks can be registered with the page framework using RegisterAsyncTask() method. Registered tasks run immediately after the PreRender event of the web form. Asynchronous operations can improve the overall performance and user responsiveness of a web application.



.NET 4.5 Beta FREE Hosting with ASPHostCentral.com

clock March 14, 2012 08:40 by author Administrator

ASPHostCentral.com, the leader in ASP.NET and Windows Hosting Provider, proudly announces that we will support ASP.NET 4.5 Hosting.

To support Microsoft ASP.NET 4.5 Beta Framework, we gladly inform you that we provide this beta account FREE of charge for a limited time (* terms and conditions apply).


The followings are the features you will get under this FREE ASP.NET 4.5 BETA Account:                

- .NET 4.5 Beta Framework
- 1 Website/Domain
- 100 MB disk space
- 100 MB bandwidth
- 50 MB SQL 2008 space
- 24/7 FTP access
- Windows Server 2008 Platform

 If you want to participate in this Beta program, there are several rules you need to understand:              

- As this is a beta version, not all the features are available. They may be some issues on this beta framework, which will be fixed upon the full release of ASP.NET 4.5 Framework
- ASPHostCentral.com does not guarantee the uptime of the sandbox solution. Additionally, we do not keep/store any backup of your files/accounts
- ASPHostCentral.com does not guarantee rapid response to any inquiries raised by a user
- This free account is only meant for testing. Users should not use it to store a production, personal, e-commerce or any blog-related site
- This free account is used to host any ASP.NET 4.5 beta website only. Any questions that are not related to ASP.NET 4.5 beta will not be responded. A user shall not host any non-ASP.NET 4.5 site on this free account either
- ASPHostCentral.com reserves full rights to terminate this beta program at any time. We will provide a notification on our Help Desk System prior to the termination of this program
- ASPHostCentral.com reserves full rights to terminate a user account, in which we suspect that there is an abuse to our system
- Once this beta program is terminated, your account will be completely wiped/remove from our system.
- For details, please check
http://www.asphostcentral.com/ASPNET-45-Beta-Hosting.aspx
- This offer expires on 31st May 2012

If you want to participate on this FREE ASP.NET 4.5 Beta Program, you must register via https://secure.asphostcentral.com/BetaOrder.aspx

 



ASP.NET 4.5 Hosting :: ASP.NET 4.5 Strongly Typed Data Controls & Model Binding

clock March 8, 2012 07:43 by author Administrator

One pain point that’s dogged WebForm developers for some time is the fact that there haven’t been any strongly typed data controls.  Some of the data controls I’m speaking of include the Repeater, FormView and GridView controls.  They all used templates, which could allow you to specify a view for different operations, such as when you’re editing data compared to adding new data.

When you use these templates today, they’re using late bound expressions to bind the data.  If you’re using the GridView control, or any of the other data controls, you’ll be familiar with the Bind or Eval syntax:

<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="false">
      <Columns>
           <asp:TemplateField HeaderText="Name">
                    <ItemTemplate>
                        <asp:Label ID="lblName" runat="server" Text='<%# Bind("Name") %>'></asp:Label>
                    </ItemTemplate>
                </asp:TemplateField>
                <asp:TemplateField HeaderText="City">
                     <ItemTemplate>
                        <asp:Label ID="lblCity" runat="server" Text='<%# Bind("Address.City") %>'></asp:Label>
                     </ItemTemplate>
                </asp:TemplateField>
      </Columns>
 </asp:GridView>


One of the problems with late-bound data controls is you’re using a string to represent a property name.  If you make a mistake typing the name, you won’t see the exception until runtime.  It’s much better to catch these errors at compile time.  Thankfully Microsoft has addressed this in ASP.NET 4.5 by implementing strongly typed data controls.

Installation

Before starting any development, you’ll need to install ASP.NET 4.5.  The simplest way to do this is via the Web Platform Installer.  All of the ASP.NET 4.5 articles I’m authoring are developed in Visual Studio 2011 Developer Preview. Here’s the link to get started.

Strongly Typed Data Controls

ASP.NET 4.5 introduces strongly typed data controls in the templates.  A new ModelType property has been added to the data controls, and this allows you to specify the type of object that is bound to the control.

Setting this property will add that type to the data controls Intellisense (an autocomplete function), which means no more typing mistakes!  This removes the need to run the website to see if you’ve made any typing mistakes during development.

In this example, I’ve connected to a Northwind web service.  Using ASP.NET 4.5, I can set the ModelType to Northwind.  If the requirement is for one-way data binding, you can use the Item expression.  Bind("Name") becomes Item.Name.  The same goes for the City property.  Replace Bind("Address.City") with Item.Address.City.

<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="false"            ModelType="WebApplication2.NorthwindService.Supplier">
        <Columns>
            <asp:TemplateField HeaderText="Name">
                <ItemTemplate>
                    <asp:Label ID="lblName" runat="server" Text='<%# Item.Name %>'></asp:Label>
                </ItemTemplate>
            </asp:TemplateField>
            <asp:TemplateField HeaderText="City">
                <ItemTemplate>
                    <asp:Label ID="lblCity" runat="server" Text='<%# Item.Address.City %>'></asp:Label>
                </ItemTemplate>
            </asp:TemplateField>
        </Columns>
    </asp:GridView>


For two-way data binding, use Binditem.  So using the example above, data binding to a text box would be like this:

<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="false"            ModelType="WebApplication2.NorthwindService.Supplier">
        <Columns>
            <asp:TemplateField HeaderText="Name">
                <ItemTemplate>
                    <asp:TextBox ID="txtName" runat="server" Text='<%# Binditem.Name %>'></asp:TextBox>
                </ItemTemplate>
            </asp:TemplateField>
            <asp:TemplateField HeaderText="City">
                <ItemTemplate>
                    <asp:TextBox ID="txtCity" runat="server" Text='<%# Binditem.Address.City %>'></asp:TextBox>
                </ItemTemplate>
            </asp:TemplateField>
        </Columns>

    </asp:GridView>

Intellisense is available, so there’ll be no more mistyped properties you only find out about at runtime.

Model Binding

Model binding focuses on coded data access logic.  Previously if you wanted to display data in the GridView control, you either had to explicitly set the DataSource property and call its DataBind method from the code behind.  Like this example:

protected void Page_Load(object sender, EventArgs e)
{
     var products = GetProducts();
     GridView1.DataSource = products;
     GridView1.DataBind();
}

Alternatively you could use one of the many data source controls to bind the data to the GridView.  Now that model binding is part of ASP.NET, you can explicitly tell the GridView which method to call to retrieve its data by using the SelectMethod property.  Here’s the updated GridView.

<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="false"            ModelType="WebApplication2.NorthwindService.Supplier"
            SelectMethod="GetProducts">
        <Columns>
            <asp:TemplateField HeaderText="Name">
                <ItemTemplate>
                    <asp:Label ID="lblName" runat="server" Text='<%# Item.Name %>'></asp:Label>
                </ItemTemplate>
            </asp:TemplateField>
            <asp:TemplateField HeaderText="City">
                <ItemTemplate>
                    <asp:Label ID="lblCity" runat="server" Text='<%# Item.Address.City %>'></asp:Label>
                </ItemTemplate>
            </asp:TemplateField>
        </Columns>
    </asp:GridView>


And in the code behind, here’s the GetProducts method:

public IQueryable<NorthwindService.Supplier> GetProducts()
{
    var service = new NorthwindService.DemoService(new Uri(@"http://services.odata.org/OData/OData.svc/"));
    var suppliers = (from p in service.Suppliers
                             select p);
    return suppliers;
}


This method doesn’t need to be in the code behind. It could live in another class or assembly.  The benefit of returning IQueryable  is that it enables deferred execution on the query, and allows a data-bound control to further modify the query before executing it.  This is useful when you need to implement sorting and paging methods.

I’m excited by the model binding and strongly bound data controls in ASP.NET 4.5.  It has certainly borrowed these ideas and concepts from MVC, so fingers crossed more of them are implemented in upcoming versions



ASP.NET Hosting :: Working with ASP.NET Cookies

clock January 31, 2012 09:53 by author Administrator

 

 

Introduction

Cookies are also known by many names, HTTP Cookie, Web Cookie, Browser Cookie, Session Cookie, etc. Cookies are one of several ways to store data about web site visitors during the time when web server and browser are not connected. Common use of cookies is to remember users between visits. Practically, cookie is a small text file sent by web server and saved by web browser on client machine.

Use of Cookies?

Cookies may be used for authentication, identification of a user session, user's preferences, shopping cart contents, or anything else that can be accomplished through storing text data. Cookies can also be used for travelling of data from one page to another.

Is Cookies Secured?

Well, this question has no specific answers in YES or NO. Cookies could be stolen by hackers to gain access to a victim's web account. Even cookies are not software and they cannot be programmed like normal executable applications. Cookies cannot carry viruses and cannot install malware on the host computer. However, they can be used by spyware to track user's browsing activities.

Using Cookies

Creating/Writing Cookies

There are many ways to create cookies, I am going to outline some of them below:

Way 1 (by using HttpCookies class)
//First Way
HttpCookie StudentCookies = new HttpCookie("StudentCookies");
StudentCookies.Value = TextBox1.Text;
StudentCookies.Expires = DateTime.Now.AddHours(1);
Response.Cookies.Add(StudentCookies);

Way 2 (by using Response directly)
//Second Way
Response.Cookies["StudentCookies"].Value = TextBox1.Text;
Response.Cookies["StudentCookies"].Expires = DateTime.Now.AddDays(1);


Way 3 (multiple values in same cookie)
//Writing Multiple values in single cookie
Response.Cookies["StudentCookies"]["RollNumber"] = TextBox1.Text;
Response.Cookies["StudentCookies"]["FirstName"] = "Abhimanyu";
Response.Cookies["StudentCookies"]["MiddleName"] = "Kumar";
Response.Cookies["StudentCookies"]["LastName"] = "Vatsa";
Response.Cookies["StudentCookies"]["TotalMarks"] = "499";
Response.Cookies["StudentCookies"].Expires = DateTime.Now.AddDays(1);


Reading/Getting Cookies

In the above code, I have used many ways to write or create cookies so I need to write here using all the above ways separately.

For Way 1
string roll = Request.Cookies["StudentCookies"].Value; //For First Way

For Way 2
string roll = Request.Cookies["StudentCookies"].Value;  //For Second Way

For Way 3
//For Multiple values in single cookie
string roll;
roll = Request.Cookies["StudentCookies"]["RollNumber"];
roll = roll + " " + Request.Cookies["StudentCookies"]["FirstName"];
roll = roll + " " + Request.Cookies["StudentCookies"]["MiddleName"];
roll = roll + " " + Request.Cookies["StudentCookies"]["LastName"];
roll = roll + " " + Request.Cookies["StudentCookies"]["TotalMarks"];
Label1.Text = roll;


Deleting Cookies

In the above code, I have used many ways to create or read cookies. Now look at the code given below which will delete cookies.

if (Request.Cookies["StudentCookies"] != null)
{
    Response.Cookies["StudentCookies"].Expires = DateTime.Now.AddDays(-1);    Response.Redirect("Result.aspx");  //to refresh the page
}


Understanding HttpCookie Class It contains a collection of all cookie values.

We do not need to use any extra namespaces for HttpCookies class (we already have used this in Way 1 above), because this class is derived from System.Web namespaces. HttpCookies class lets us work with cookies without using Response and Request objects (we have already used this in Way 2 and Way 3 above).

HttpCookie class has a list of some properties, let us outline them.

    * Domain: It contains the domain of the cookie.
    * Expires: It contains the expiration time of the cookie.
    * HasKeys: It contains True if the cookie has subkeys.
    * Name: It contains the name of the cookie.
    * Path: It contains the virtual path to submit with the cookie.
    * Secure: It contains True if the cookie is to be passed in a secure connection only.
    * Value: It contains the value of the cookie.
    * Values:

Limitations of Cookies

There are following limitations for cookies:
   1. Size of cookies is limited to 4096 bytes.
   2. Total 20 cookies can be used on a single website; if you exceed this browser will delete older cookies.
   3. End user can stop accepting cookies by browsers, so it is recommended to check the users’ state and prompt the user to enable cookies.

Sometimes, the end user disables the cookies on browser and sometimes browser has no such feature to accept cookies. In such cases, you need to check the users’ browser at the home page of website and display the appropriate message or redirect on appropriate page having such message to enable it first. The following code will check whether the users’ browser supports cookies or not. It will also detect if it is disabled too.

protected void Page_Load(object sender, EventArgs e)
{
    if (Request.Browser.Cookies)
    {
        //supports the cookies
    }
    else
    {
        //not supports the cookies
        //redirect user on specific page
        //for this or show messages
    }
}


It is always recommended not to store sensitive information in cookies

 

 

 



ASP.NET 4.5 Hosting :: Model Binding Feature in ASP.NET 4.5

clock November 28, 2011 10:05 by author Administrator

The Good News - In ASP.NET 4.5, we can adopt an approach using which the Model can be directly bound with the DataBound controls and CRUD and pagination operations can be implemented very effectively. It incorporates concepts from the ObjectDataSource control and from model binding in ASP.NET MVC. We will see this shortly. ASP.NET 4.5 is based upon .NET 4.5 and it gets installed once you install Visual Studio 2011 preview. 

Note: If you want to install Visual Studio 2011 preview, you can also use the Windows 8 Developer preview.

In this article I will be explaining a new ASP.NET 4.5 exciting feature called ‘Model Binding with Web Forms’. Up to previous versions, webforms for data-binding used to make use of the ‘Eval’ method. During runtime, calls to Eval makes use of reflection against the currently bound data object and reads value of the member with the given name in Eval method. (Read Why Eval is Evil). Once this value is read the result is displayed in HTML. Although this is easiest way of data-binding, it has limitations like checking the binding name during compilation time etc.

Update: Also check out the second part of this article ASP.NET 4.5: Filtering using Model Binding in ASP.NET Web Forms

In ASP.NET 4.5 the Model Binding has improved. We will be going through the complete model binding feature using the following steps:

- Model binding with Web Forms.
- Value Providers.
- Filtering.
- Performing Update Operations.

For this article I am using Sql Server 2008 R2 and a ‘Company’ database, with following Tables:

Department - DeptNo (int) Primary Key, Dname (varchar(50)),Location (varchar(50)).
Employee - EmpNo (int) Primary Key, EmpName (varchar(50)),Salary (int), DeptNo(int) Forwign Key.

Let’s get started.

Step 1: Open Visual Studio 2011 Developer Preview and create a new Web Application, make sure that the Framework version you select is .NET 4.5. Call this application ‘ASPNET45_ModelBinding’.

Step 2: In this project, add new folders and name them as Model and Department. In the Department folder, add two Web Forms (with master page). Name them as ‘Departments.aspx’ and ‘DepartmentDetails.aspx’.

Step 3: In the Model folder, add a new ADO.NET entity data model and name it as ‘CompanyEDMX.edmx’. In the Wizard, select Company Database and select Department and Employee table. After the completion of wizard, the below result will be displayed:


Step 4: Open the Departments.aspx in the ‘Source’ view and add the Repeater control in it with the Department model bound to it as below.

The above code shows some modified databound features for DataBound controls in ASP.NET 4.5. The Department Model is assigned to the ‘ModelType’ property of the repeater. This property is available to all DataBound controls. This allows us to define the type of data that is bound to the control and also allows to bind properties of the Model inside the control. The above code defines ‘ItemTemplate’ inside the repeater control which refers to the ‘DepartmentDetails.aspx’ by passing DeptNo value using QueryString to it.


Step 5: Go to the Departments.aspx.cs code behind, and write the following code:

The above code sets the datasource property for the repeater control.


Step 6: View the Departments.aspx inside the browser and the following result will be displayed:  
In your OS, observe the lower right corner of the System Tray. Instead of the ASP.NET Development server, ASP.NET 4.5 uses IIS Express as shown below:  





Step 7
: In Step 4, we added the repeater control which has the ItemsTemplate and contains an <a href=””> to navigate to DepartmentDetails.aspx using a query string. This page is designed for displaying details of a particular Department. Open DepartmentDetails.aspx in the ‘Source’ view and add a DetailsView web UI databound control inside it. As explained Step 4, we need to assign the ModelType property of this control to ‘Department’ model.

All those who have used controls like DetailsView or FormView knows that these control are used for performing DML operations. Now to perform DML operations in earlier versions of ASP.NET i.e. from 2.0 to 4.0 we used to make use of ObjectDataProvider and this provider was usually configured using Get,Insert,Update and Delete methods form the source object. However the ASP.NET 4.5 DataBound controls e.g. GridView, FormView, DetailsView etc, exposes the following properties:

- SelectMethod: Used to make call to a method which returns IEnumarable.
- InsertMethod: Used to make call to a method which performs Insert operation.
- UpdateMethod: Used to make call to a method which performs Update operation.
- DeleteMethod: Used to make call to a method which performs Delete operation.

Configure the DepartmentDetails.aspx as shown below:


Step 8: Open the DepartmentDetails.aspx.cs and add the following code in it:    


Now carefully have a look at the above methods. None of these methods make use of any of the UI controls in the user interface. All these methods strictly work on Model objects and this feature drastically reduces additional coding. One more important fact is, if you observe the ‘GetDepartment()’ method, it has defined the ‘DeptNo’ input parameter with the QueryString Value provider. This automatically reads the DeptNo in the QueryString and displays the Department details inside the DetailsView.

Note: In previous versions of ASP.NET we could have done this using Request.QueryString[“DeptNo”]

Step 9: Now open Site.Master and add the following menu item:

<asp:MenuItem NavigateUrl="~/Department/Departments.aspx" Text="Departments"/>

Step 10: Make Default.aspx as a startup page and run the application. You will see the Default.aspx with Department and Employee menu. Once you click on ‘Department’ menu, Departments.aspx will be displayed. Now click on any Department and you will be transferred to ‘DepartmentDetails.aspx’ as below:

The QueryString has the DeptNo and based upon the value of the DeptNo, the DetailsView will display the  Department details. Here you can now test the Update and New (insert) functionality.

Check out the second part of this article ASP.NET 4.5: Filtering using Model Binding in ASP.NET Web Forms

Conclusion: The Model binding feature provides facility to the developers to develop Webforms which can be independent from the Model

 

 

 

 

 

 

 

 



ASP.NET 4.0 Hosting :: The Reasons Application Pool Recycle

clock October 31, 2011 07:43 by author Administrator

If your ASP.NET application crashes, has an unhandled exception, hangs or otherwise becomes brain-dead, it will cause the application pool to recycle. Sometimes your application pool recycles for no obvious reason. This is usually a configuration issue or it may be caused by your app performing file system operations in the application directory. Many times developers incorrectly set up SqlConnections so that they aren't properly closed and returned to the connection pool, and this can also cause your AppPool to recycle unexpectedly. When your AppPool recycles, you can kiss your InProc Sessions - and everything else -- goodbye.

Application pool settings

Looking at the properties for the application pool in IIS, you'll see the settings for "on purpose" recycling. In IIS6 these are:

- Recycle worker processes (in minutes)
- Recycle worker process (in requests)
- Recycle worker processes at the following times
- Maximum virtual memory
- Maximum used memory

If you're running IIS5 or the IIS5 isolation mode you must look at the processModel element of machine.config. The properties you should pay attention to are:

- memoryLimit
- requestLimit
- timeout

In IIS 7.o, you have Fixed Interval or Fixed # Requests, or Specific Times for recycling. Also, there are Memory -based Maximums for Virtual and Private Memory, and additional items for Configurable and Runtime recycling events including "unhealthy ISAPI".

When an application pool recycles, HTTP.SYS holds onto the client connection in kernel mode while the user mode worker process recycles. After the process recycle, HTTP.SYS transparently routes the new requests to the new worker process. Consequently, the client never "loses all connectivity" to the server; the TCP connection is not lost -- only state is lost (Application, Session, Cache, etc.).

memoryLimit
The default value of memoryLimit is 60. This value is only useful if you have a small amount memory on a 32 bit machine. "60" means 60% of total system memory. So if you have 1 GB of memory your IIS worker process will automatically restart once it hits memory usage of 600 MB.

requestLimit
This setting is "infinite" by default, but if it is set to 8000 for example, then ASP.NET will launch a new worker process once it has handled 8000 requests.

timeout
The default timeout is "infinite". This is where you set the lifetime of the worker process. Once the timeout is reached ASP.NET launches a new worker process, so setting this to "00:30:00" would recycle your application every 30 minutes.

Other properties
Another property within the processModel element that will cause your application pool to recycle is responseDeadlockInterval. If you have a deadlock then that's your main "fix" that you need to worry about -- changing the responseDeadlockInterval setting won't do much to resolve the problem. You need to deal with the deadlock itself, find out why it's happening, and change your code.

File Change Notification

ASP.NET 2.0 depends on File Change Notifications (FCN) to see if the application has been updated, and depending on the magnitude of change the application pool will recycle. If you or your application are adding and removing directories to the application folder, then you will be restarting your application pool every time.

Altering the following files also causes an immediate restart of the application pool:
- web.config
- machine.config
- global.asax
- Any file in the /bin directory or subfolders

Updating .aspx files, etc. causing a recompile eventually triggers a restart of the application pool also. There is a property of the compilation element under system.web called numRecompilesBeforeAppRestart. The default value is 20, meaning that after 20 recompiles the application pool will recycle.

Workaround for the sub-directory issue

If your application actually requires adding and removing sub-directories you can use linkd to create what's called a directory junction:

Create a directory you'd like to exclude from FCN, e.g. c:\inetpub\wwwroot\MyWebApp\MyFolder
Create a separate folder somewhere outside the wwwroot, e.g. c:\MyExcludedFolder
Use linkd to link the two: linkd c:\inetpub\wwwroot\MyWebApp\MyFolder c:\MyExcludedFolder
Now any changes made in the c:\inetpub\wwwroot\MyWebApp\MyFolder will now actually occur in c:\MyExcludedFolder so they will not be sensed by FCN.

Linkd only comes with the Windows XX Resource Kit, which is a pretty big download. But Mark Russinovitch has "junction" which could be even better:
http://www.microsoft.com/technet/sysinternals/FileAndDisk/Junction.mspx  

Is recycling the application pool good or bad?


If your app is coded properly, you shouldn't have to recycle the application pool. However, if you're dealing with a memory leak in your app and you need to buy time to fix it, then recycling the application pool could be a good idea. It's important to understand, though, that's not a "Fix" - it's just a "Band-Aid" until you find out what's causing the problem and fix your code. Unlike as with ASP.NET 1.1, in ASP.NET 2.0 if your app generates an unhandled exception the AppDomain will unload causing an application pool recycle. Consequently it is extremely important to ensure that your code is "best practices" and doesn't generate unhandled exceptions except under the most extreme and unusual conditions



ASP.NET 4.0 & ASP.NET 4.5 Hosting

 

ASPHostCentral is a premier web hosting company where you will find low cost and reliable web hosting. We have supported the latest ASP.NET 4.5 hosting and ASP.NET MVC 4 hosting. We have supported the latest SQL Server 2012 Hosting and Windows Server 2012 Hosting too!

 

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