= async/await =
Example:
<code php>
private int slowFunc(int a, int b)
{
   System.Threading.Thread.Sleep(10000);
   return a + b;
}
</code>

In C# 4.0, you have to use ''ContinueWith()'':
<code php>
private void btnProcessTask_Click(object sender, EventArgs e)        
{
   this.btnProcessTask.Enabled = false;          
   var uiScheduler = TaskScheduler.FromCurrentSynchronizationContext();  // get UI thread context 
   var someTask = Task<int>.Factory.StartNew(() => slowFunc(1, 2));      // create and start the Task 
   someTask.ContinueWith(x =>     
     {                                          
        this.lblTaskResults.Text = "Result: " + someTask.Result.ToString();   
        this.btnProcessTask.Enabled = true;   
     }, uiScheduler  
    );        
}
</code>

In C# 5.0, you can use ''async/await'':
  * Add ''async'' to click event definition.
  * Add ''await'' to task needing asynchronous access.   As Eric Lippert [[http://blogs.msdn.com/b/ericlippert/archive/2010/10/29/asynchronous-programming-in-c-5-0-part-two-whence-await.aspx|mentioned]], the ''await'' operator means “if the task we are awaiting has not yet completed, then sign up the rest of this method as the continuation of that task, and then return to your caller immediately; the task will invoke the continuation when it completes.”
<code php>
private async void btnProcessTask_Click(object sender, EventArgs e)
{
   this.btnProcessTask.Enabled = false; 
   var someTask = Task<int>.Factory.StartNew(() => slowFunc(1, 2)); 
   await someTask;  
   this.lblTaskResults.Text = "Result: " + someTask.Result.ToString(); 
   this.btnProcessTask.Enabled = true;
}
</code>

== References ==
  * [[http://www.itwriting.com/blog/4913-a-simple-example-of-async-and-await-in-c-5.html|Example of async and await in C# 5]]
  * [[http://blogs.msdn.com/b/ericlippert/archive/2010/10/29/asynchronous-programming-in-c-5-0-part-two-whence-await.aspx|Asynchronous Programming in C# 5.0]]