private async void StartButton_Click(object sender, RoutedEventArgs e)

{

    // ExampleMethodAsync returns a Task<int>, which means that the method

    // eventually produces an int result. However, ExampleMethodAsync returns

    // the Task<int> value as soon as it reaches an await.

    ResultsTextBox.Text += "\n";

    try

    {

        int length = await ExampleMethodAsync();

        // Note that you could put "await ExampleMethodAsync()" in the next line where

        // "length" is, but due to when '+=' fetches the value of ResultsTextBox, you

        // would not see the global side effect of ExampleMethodAsync setting the text.

        ResultsTextBox.Text += String.Format("Length: {0}\n", length);

    }

    catch (Exception)

    {

        // Process the exception if one occurs.

    }

}

public async Task<int> ExampleMethodAsync()

{

    var httpClient = new HttpClient();

    int exampleInt = (await httpClient.GetStringAsync("http://msdn.microsoft.com")).Length;

    ResultsTextBox.Text += "Preparing to finish ExampleMethodAsync.\n";

    // After the following return statement, any method that's awaiting

    // ExampleMethodAsync (in this case, StartButton_Click) can get the

    // integer result.

    return exampleInt;

}

// Output:

// Preparing to finish ExampleMethodAsync.

// Length: 53292

private async void button_Click(object sender, RoutedEventArgs e)

{

  TB_Result.Text = await exampleAsync();

}

 private async Task<string> exampleAsync()

  {

     return await Task.Run(() =>

     {

         WebClient w = new WebClient();

         w.DownloadFile("http://provissy.com", "webPage1");

         w.DownloadFile("http://microsoft.com", "webPage2");

         string a = w.DownloadString("http://microsoft.com");

         return a;

      });

 }