How to read to end process output asynchronously in C#?

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Process.WaitForExit() will wait until the asynchronous output / error stream reading finished. Unfortunately this is not true for Process.WaitForExit(timeout) overload. This is what the Process class does internally:

//…

finally
{
    if (processWaitHandle != null)
    {
        processWaitHandle.Close();
    }
    if (this.output != null && milliseconds == -1)
    {
        this.output.WaitUtilEOF();
    }
    if (this.error != null && milliseconds == -1)
    {
        this.error.WaitUtilEOF();
    }
    this.ReleaseProcessHandle(safeProcessHandle);
}

… So it will wait for the async reads only if there was no timeout!
To fix it simply call the parameterless WaitForExit() after WaitForExit(timeout) returned true:

// …

if (process.WaitForExit( 10 * 1000 ) && process.WaitForExit() )
{
 // Process'es OutputDataReceived / ErrorDataReceived callbacks will not be called again, EOF streams reached
}
else
{
   throw new Exception("timeout");
}

For details read the remarks here: http://msdn.microsoft.com/en-us/library/ty0d8k56%28v=vs.110%29

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