Differences

This shows you the differences between two versions of the page.

--- swdev:dotnet:actions [2010/11/10 11:00]
smayr created
+++ swdev:dotnet:actions [2011/01/26 16:55] (current)
smayr [Example]
@@ Line 1: / Line 1: @@
 == Actions ==
+Definition
+<code csharp>
+Action<int> example1 =
+   (int x) => Console.WriteLine("Write {0}", x);
+Action<int, int> example2 =
+   (x, y) => Console.WriteLine("Write {0} and {1}", x, y);
+Action example3 =
+   () => Console.WriteLine("Done");
+</code>
+== Using Actions to Communicate Between Background Worker and Main Threads ==
+<code csharp>
+using System.Windows.Threading;  // in WindowsBase.dll
+public partial class MyWindow : Window
+{
+  public MyWindow()
+  {
+    InitializeComponent();
+    new Thread (Work).Start();
+  }
+  void Work()
+  {
+    Thread.Sleep (5000);           // Simulate time-consuming task
+    UpdateMessage ("The answer");
+  }
+  void UpdateMessage (string message)
+  {
+    Action action = () => txtMessage.Text = message;
+    Dispatcher.Invoke (action);
+  }
+}
+</code>
+Source:
+  * [[http://www.albahari.com/threading/part2.aspx#_Rich_Client_Applications|Threading (Part 2): Rich Client Applications and Thread Affinity]]
+== Example ==
+<code csharp>
+///----------------------------------------------------------------------------------------
+/// <summary>
+/// Close the popup menu.
+/// </summary>
+///----------------------------------------------------------------------------------------
+public void Close()
+{
+    //----------------------------------------------------------------------------
+    // Deal with cross thread ownership of UI control instance
+    // by invoking an action delegate. In other words,
+    // popupmnu is owned by thread that instantiated it (when Open() was called),
+    // so we cannot close popmnu arbitrarily.  We need the help of
+    // the owner thread's Dispatcher to execute the Close() for us.
+    //----------------------------------------------------------------------------
+    //Action action = () => popmnuReports.IsOpen = false;
+    Action action = this.CloseDelegate();
+    this.Dispatcher.BeginInvoke(action);
+}
+///----------------------------------------------------------------------------------------
+/// <summary>
+/// Close method deletegate, used by cross thread dispatcher.
+/// </summary>
+/// <returns></returns>
+///----------------------------------------------------------------------------------------
+private Action CloseDelegate()
+{
+    return delegate()
+    {
+        popmnuFitting.IsOpen = false;
+        m_TimerForDisplay.Enabled = false;
+    };
+}
+</code>
 == Resources ==
   * [[http://dotnetperls.com/action|DotNetPerls: Action]]
   * [[http://msdn.microsoft.com/en-us/library/018hxwa8.aspx|MSDN: Action of Delete]]
   * [[http://stackoverflow.com/questions/371054/uses-of-action-delegate-in-c|StackOverflow: Use of Action Delete in C#]]
+  * [[http://weblogs.asp.net/cschittko/archive/2008/05/14/wpf-ui-update-from-background-threads.aspx|WPF UI Update from Background Threads]]