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POCalling an external process in C#/WinForms makes UI unresponsive. Why?
 

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  1. POCalling an external process in C#/WinForms makes UI unresponsive. Why?
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    <p>I have a Winforms app that lives in the taskbar area. A window opens up for logging output.</p> <p>Now, in my component (still on UI Thread here) I need to call an external process that runs 5-15min and produces files. I need to wait for the process to exit and consume those files.</p> <p>Since I want my UI to be responsive (move the Window, etc.) I implemented an agent and am calling the process with BeginInvoke/EndInvoke:</p> <pre><code>private delegate int BeginCallDelegate( int port, int baud, int timeout, Job job ); private BeginCallDelegate del = null; public IAsyncResult BeginCall( int port, int baud, int timeout, Job job ) { del = new BeginCallDelegate( Call ); IAsyncResult iar = del.BeginInvoke( port, baud, timeout, job, null, null ); return iar; } </code></pre> <p>In the calling code I am polling the IAsyncResult with WaitOne() but notice that the UI is extremely <em>unresponsive</em> if not <em>frozen</em>:</p> <pre><code>IAsyncResult a = agent.BeginCall(...); //BeginInvoke while ( !a.IsCompleted ) { iar.AsyncWaitHandle.WaitOne( 250 ); //writing something to a textbox works here, but overall responsiveness is weak } agent.EndCall( iar ); //EndInvoke </code></pre> <p><strong>VS tells me the external process is started on a worker thread, but why does that not help with my UI responsiveness? IT should NOT block the calling thread</strong></p> <p>Here's the code that launches the process:</p> <pre><code>ProcessStartInfo psi = new ProcessStartInfo(); psi.FileName = "app.exe"; psi.Arguments = String.Format( "blah blah", port, baud, timeout, job.FullName ); psi.CreateNoWindow = false; psi.ErrorDialog = false; psi.WindowStyle = ProcessWindowStyle.Hidden; process.StartInfo = psi; if ( !process.Start() ) throw new Exception( "The process cannot start." ); process.WaitForExit( job.Timeout ); </code></pre> <p><em><strong>Hint: To test, the external app.exe is a dummy app that does nothing else but Thread.Sleep(60000). CPU Load is 3%.</em></strong></p> <p><strong>Another question: How would I do this the "TPL way" without using Begin/EndInvoke?</strong></p>
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      1. POCalling an external process in C#/WinForms makes UI unresponsive. Why?
      1. USInfinite Possibilities
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      1. POCalling an external process in C#/WinForms makes UI unresponsive. Why?
      1. USGennady Vanin Геннадий Ванин
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    1. COYou are committing one of the Great Sins of GUI programming, you are blocking the UI thread with your while loop. That it isn't completely dead is because calling WaitOne() on a UI thread is illegal, the CLR pumps a message loop to keep it alive. You will need to get rid of that while loop. Easy to do, the Process class has an Exited event.
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      1. POCalling an external process in C#/WinForms makes UI unresponsive. Why?
      1. USHans Passant
 

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