Task-Based Async Pattern in WCF 4.5

In Visual Studio 2012 and WCF 4.5, there is a new option available to generate task-based operations so that the code from the client-side can then be less complex. Task-based asynchronous programming is now simplified and streamlined in .NET 4.5 by the keywords "await" and "async".
Sample WCF Application

Step 1: Open VS2012 and create a blank solution, name it "WCF_Task_Based_WCFService". In this solution add a new WCF Service application project targeting the .NET 4.5 Framework. Name this project "WCF_TaskBasedService".
Step 2: Add the following code to IService.cs:

using System.ServiceModel;

namespace WCF_TaskBasedService

// NOTE: You can use the "Rename" command on the "Refactor" menu to change the interface name "IService1" in both code and config file together.


    public interface IService1



        List<EmployeeInfo> GetEmployees();


    // Use a data contract as illustrated in the sample below to add composite types to service operations.


    public class EmployeeInfo



        public int EmpNo { get; set; }


        public string EmpName { get; set; }


Step 3: Implement the ServiceContract as below:

public class Service : IService
    EmployeeInfo[] Employees = null;

    public class Service1 : IService1


        List<EmployeeInfo> lstEmployee = null;

        public Service1()


            lstEmployee = new List<EmployeeInfo>{  

            new EmployeeInfo() {EmpNo=1,EmpName="A"},

            new EmployeeInfo() {EmpNo=2,EmpName="B"},

            new EmployeeInfo() {EmpNo=3,EmpName="C"},

            new EmployeeInfo() {EmpNo=4,EmpName="D"},

            new EmployeeInfo() {EmpNo=4,EmpName="E"},

            new EmployeeInfo() {EmpNo=5,EmpName="F"},

            new EmployeeInfo() {EmpNo=6,EmpName="G"},

           new EmployeeInfo() {EmpNo=7,EmpName="H"},

           new EmployeeInfo() {EmpNo=8,EmpName="I"},

          new EmployeeInfo() {EmpNo=9,EmpName="J"}



    public List<EmployeeInfo> GetEmployees()


        return lstEmployee;



Step 4: Build the service and publish it in IIS (optional).
Step 5: In the same solution, add a new WPF Project targeted to .NET 4.5 and name it "WPF_Client". Design the MainWindow.xaml as below:



            <DataGrid  x:Name="dgEmp"  HorizontalAlignment="Left" Margin="74,26,0,0"  VerticalAlignment="Top"

  Height="338" Width="650"/>

            <Button  x:Name="btnGetEmployees"  Content="Get Employees" HorizontalAlignment="Left"

  Margin="74,389,0,0"  VerticalAlignment="Top" Width="650" Height="76"


            <TextBlock  x:Name="txtInfo"  HorizontalAlignment="Left"  Margin="74,470,0,0"  TextWrapping="Wrap"

  Text="TextBlock"  VerticalAlignment="Top"  Height="38" Width="650"/>



Step 6: Add the WCF Service Reference to the project:

WCF Service Reference

  • In the "Add Service" window, enter an address of the WCF Service.

    address of the WCF Service

  • Click on Go and click on the Radio Button "Generate Task-based" as below:

    Radio Button Generate Task

This adds the proxy in the WPF application. If you open the proxy class then the method "GetEmployeeAsync" is generated as follows:

proxy in the WPF application

Step 7: Now the preceding method can be called in the WPF application on the Click event of the button:

private async void btnGetEmployees_Click(object sender, RoutedEventArgs e)


    txtInfo.Text = "Data is Not Received Yet....";

    EmployeeService.Service1Client Proxy = new EmployeeService.Service1Client();

    var Result = await Proxy.GetEmployeesAsync();

    dgEmp.ItemsSource = Result;

    txtInfo.Text = "Data Received....";

If you look carefully at the code above, you will find that the Click event method is decorated with the "async" keyword. This indicates that the method contains an Async call. The method "GetEmployeeAsync" is called with the "await" keyword, this means that the asynchronous call will be completed and then the data will be displayed in the DataGrid.
Step 8: Run the application and click on the Button. The result will be as shown below:

Run the application
The Text shows that the call is in progress. Wait for 10 seconds and the result will be as follows:


Using the Task-Based Async Pattern, we can program in a more linear fashion that is easy to read compared to the Event Based Async Pattern (EAP), where you have one method initiating the call and another method handling the callback after the task is completed. Thus by exposing task-based operations to the client, the client-side code can be made less complex.
Download the source code for reference. Happy Coding.

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