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POAsynchronous WPF Commands
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copied!<p><strong><em>Note</strong>: The code in this question is part of <a href="http://www.codeplex.com/desleeper" rel="noreferrer">deSleeper</a> if you want the full source.</em></p> <p>One of the things I wanted out of commands was a baked design for asynchronous operations. I wanted the button pressed to disable while the command was executing, and come back when complete. I wanted the actual work to be performed in a ThreadPool work item. And lastly, I wanted a way to handle any errors that occurred during the asynchronous processing.</p> <p>My solution was an AsyncCommand:</p> <pre><code>public abstract class AsyncCommand : ICommand { public event EventHandler CanExecuteChanged; public event EventHandler ExecutionStarting; public event EventHandler<AsyncCommandCompleteEventArgs> ExecutionComplete; public abstract string Text { get; } private bool _isExecuting; public bool IsExecuting { get { return _isExecuting; } private set { _isExecuting = value; if (CanExecuteChanged != null) CanExecuteChanged(this, EventArgs.Empty); } } protected abstract void OnExecute(object parameter); public void Execute(object parameter) { try { IsExecuting = true; if (ExecutionStarting != null) ExecutionStarting(this, EventArgs.Empty); var dispatcher = Dispatcher.CurrentDispatcher; ThreadPool.QueueUserWorkItem( obj => { try { OnExecute(parameter); if (ExecutionComplete != null) dispatcher.Invoke(DispatcherPriority.Normal, ExecutionComplete, this, new AsyncCommandCompleteEventArgs(null)); } catch (Exception ex) { if (ExecutionComplete != null) dispatcher.Invoke(DispatcherPriority.Normal, ExecutionComplete, this, new AsyncCommandCompleteEventArgs(ex)); } finally { dispatcher.Invoke(DispatcherPriority.Normal, new Action(() => IsExecuting = false)); } }); } catch (Exception ex) { IsExecuting = false; if (ExecutionComplete != null) ExecutionComplete(this, new AsyncCommandCompleteEventArgs(ex)); } } public virtual bool CanExecute(object parameter) { return !IsExecuting; } } </code></pre> <p>so the question is: Is all this necessary? I've noticed built in asynchronous support for data-binding, so why not command execution? Perhaps it's related to the parameter question, which is my next question.</p>

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