namespace AsyncFirstExample 
{ 
    public partial class MainWindow : Window 
    { 
        // Mark the event handler with async so you can use await in it. 
        private async void StartButton_Click(object sender, RoutedEventArgs e) 
        { 
            // Call and await separately. 
            //Task<int> getLengthTask = AccessTheWebAsync(); 
            //// You can do independent work here. 
            //int contentLength = await getLengthTask; 
 
            int contentLength = await AccessTheWebAsync(); 
 
            resultsTextBox.Text += 
                String.Format("\r\nLength of the downloaded string: {0}.\r\n", contentLength); 
        } 
 
 
        // Three things to note in the signature: 
        //  - The method has an async modifier.  
        //  - The return type is Task or Task<T>. (See "Return Types" section.) 
        //    Here, it is Task<int> because the return statement returns an integer. 
        //  - The method name ends in "Async." 
        async Task<int> AccessTheWebAsync() 
        {  
            // You need to add a reference to System.Net.Http to declare client. 
            HttpClient client = new HttpClient(); 
 
            // GetStringAsync returns a Task<string>. That means that when you await the 
            // task you'll get a string (urlContents). 
            Task<string> getStringTask = client.GetStringAsync("http://msdn.microsoft.com"); 
 
            // You can do work here that doesn't rely on the string from GetStringAsync. 
            DoIndependentWork(); 
 
            // The await operator suspends AccessTheWebAsync. 
            //  - AccessTheWebAsync can't continue until getStringTask is complete. 
            //  - Meanwhile, control returns to the caller of AccessTheWebAsync. 
            //  - Control resumes here when getStringTask is complete.  
            //  - The await operator then retrieves the string result from getStringTask. 
            string urlContents = await getStringTask; 
 
            // The return statement specifies an integer result. 
            // Any methods that are awaiting AccessTheWebAsync retrieve the length value. 
            return urlContents.Length; 
        } 
 
 
        void DoIndependentWork() 
        { 
            resultsTextBox.Text += "Working . . . . . . .\r\n"; 
        } 
    } 
} 
 
// Sample Output: 
 
// Working . . . . . . . 
 
// Length of the downloaded string: 41564.