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    <p>Ideally, store a single instance of <code>Dispatcher</code> that you can use elsewhere without having the thread check on it.</p> <p>Calling any singleton .Current instance may in fact cause a cross-thread access check to be invoked. By storing it first, you can avoid this to actually get the shared instance.</p> <p>I use a "SmartDispatcher" that uses a dispatcher when called off-thread, and just invokes otherwise. It solves this sort of issue.</p> <p>Post: <a href="http://www.jeff.wilcox.name/2010/04/propertychangedbase-crossthread/" rel="noreferrer">http://www.jeff.wilcox.name/2010/04/propertychangedbase-crossthread/</a> </p> <p>Code:</p> <pre><code>// (c) Copyright Microsoft Corporation. // This source is subject to the Microsoft Public License (Ms-PL). // Please see http://go.microsoft.com/fwlink/?LinkID=131993 for details. // All other rights reserved. using System.ComponentModel; namespace System.Windows.Threading { /// &lt;summary&gt; /// A smart dispatcher system for routing actions to the user interface /// thread. /// &lt;/summary&gt; public static class SmartDispatcher { /// &lt;summary&gt; /// A single Dispatcher instance to marshall actions to the user /// interface thread. /// &lt;/summary&gt; private static Dispatcher _instance; /// &lt;summary&gt; /// Backing field for a value indicating whether this is a design-time /// environment. /// &lt;/summary&gt; private static bool? _designer; /// &lt;summary&gt; /// Requires an instance and attempts to find a Dispatcher if one has /// not yet been set. /// &lt;/summary&gt; private static void RequireInstance() { if (_designer == null) { _designer = DesignerProperties.IsInDesignTool; } // Design-time is more of a no-op, won't be able to resolve the // dispatcher if it isn't already set in these situations. if (_designer == true) { return; } // Attempt to use the RootVisual of the plugin to retrieve a // dispatcher instance. This call will only succeed if the current // thread is the UI thread. try { _instance = Application.Current.RootVisual.Dispatcher; } catch (Exception e) { throw new InvalidOperationException("The first time SmartDispatcher is used must be from a user interface thread. Consider having the application call Initialize, with or without an instance.", e); } if (_instance == null) { throw new InvalidOperationException("Unable to find a suitable Dispatcher instance."); } } /// &lt;summary&gt; /// Initializes the SmartDispatcher system, attempting to use the /// RootVisual of the plugin to retrieve a Dispatcher instance. /// &lt;/summary&gt; public static void Initialize() { if (_instance == null) { RequireInstance(); } } /// &lt;summary&gt; /// Initializes the SmartDispatcher system with the dispatcher /// instance. /// &lt;/summary&gt; /// &lt;param name="dispatcher"&gt;The dispatcher instance.&lt;/param&gt; public static void Initialize(Dispatcher dispatcher) { if (dispatcher == null) { throw new ArgumentNullException("dispatcher"); } _instance = dispatcher; if (_designer == null) { _designer = DesignerProperties.IsInDesignTool; } } /// &lt;summary&gt; /// /// &lt;/summary&gt; /// &lt;returns&gt;&lt;/returns&gt; public static bool CheckAccess() { if (_instance == null) { RequireInstance(); } return _instance.CheckAccess(); } /// &lt;summary&gt; /// Executes the specified delegate asynchronously on the user interface /// thread. If the current thread is the user interface thread, the /// dispatcher if not used and the operation happens immediately. /// &lt;/summary&gt; /// &lt;param name="a"&gt;A delegate to a method that takes no arguments and /// does not return a value, which is either pushed onto the Dispatcher /// event queue or immediately run, depending on the current thread.&lt;/param&gt; public static void BeginInvoke(Action a) { if (_instance == null) { RequireInstance(); } // If the current thread is the user interface thread, skip the // dispatcher and directly invoke the Action. if (_instance.CheckAccess() || _designer == true) { a(); } else { _instance.BeginInvoke(a); } } } } </code></pre>
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    1. COAwsome stuff, thank you!
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