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Process.OutputDataReceived Event

Occurs when an application writes to its redirected StandardOutput stream.

Namespace: System.Diagnostics
Assembly: System (in system.dll)

public event DataReceivedEventHandler OutputDataReceived
/** @event */
public void add_OutputDataReceived (DataReceivedEventHandler value)

/** @event */
public void remove_OutputDataReceived (DataReceivedEventHandler value)

In JScript, you can handle the events defined by a class, but you cannot define your own.
Not applicable.

The OutputDataReceived event indicates that the associated Process has written to its redirected StandardOutput stream.

The event is enabled during asynchronous read operations on StandardOutput. To start asynchronous read operations, you must redirect the StandardOutput stream of a Process, add your event handler to the OutputDataReceived event, and call BeginOutputReadLine. Thereafter, the OutputDataReceived event signals each time the process writes a line to the redirected StandardOutput stream, until the process exits or calls CancelOutputRead.

The following example illustrates how to perform asynchronous read operations on the redirected StandardOutput stream of the sort command. The sort command is a console application that reads and sorts text input.

The example creates an event delegate for the SortOutputHandler event handler and associates it with the OutputDataReceived event. The event handler receives text lines from the redirected StandardOutput stream, formats the text, and writes the text to the screen.

// Define the namespaces used by this sample.
using System;
using System.Text;
using System.IO;
using System.Diagnostics;
using System.Threading;
using System.ComponentModel;

namespace ProcessAsyncStreamSamples
{
    class SortOutputRedirection
    {
        // Define static variables shared by class methods.
        private static StringBuilder sortOutput = null;
        private static int numOutputLines = 0;
      
        public static void SortInputListText()
        {
            // Initialize the process and its StartInfo properties.
            // The sort command is a console application that
            // reads and sorts text input.

            Process sortProcess;
            sortProcess = new Process();
            sortProcess.StartInfo.FileName = "Sort.exe";
            
            // Set UseShellExecute to false for redirection.
            sortProcess.StartInfo.UseShellExecute = false;

            // Redirect the standard output of the sort command.  
            // This stream is read asynchronously using an event handler.
            sortProcess.StartInfo.RedirectStandardOutput = true;
            sortOutput = new StringBuilder("");

            // Set our event handler to asynchronously read the sort output.
            sortProcess.OutputDataReceived += new DataReceivedEventHandler(SortOutputHandler);

            // Redirect standard input as well.  This stream
            // is used synchronously.
            sortProcess.StartInfo.RedirectStandardInput = true;
  
            // Start the process.
            sortProcess.Start();

            // Use a stream writer to synchronously write the sort input.
            StreamWriter sortStreamWriter = sortProcess.StandardInput;

            // Start the asynchronous read of the sort output stream.
            sortProcess.BeginOutputReadLine();

            // Prompt the user for input text lines.  Write each 
            // line to the redirected input stream of the sort command.
            Console.WriteLine("Ready to sort up to 50 lines of text");

            String inputText;
            int numInputLines = 0;
            do 
            {
                Console.WriteLine("Enter a text line (or press the Enter key to stop):");
            
                inputText = Console.ReadLine();
                if (!String.IsNullOrEmpty(inputText))
                {
                    numInputLines ++;
                    sortStreamWriter.WriteLine(inputText);
                }
            }
            while (!String.IsNullOrEmpty(inputText) && (numInputLines < 50));
            Console.WriteLine("<end of input stream>");
            Console.WriteLine();

            // End the input stream to the sort command.
            sortStreamWriter.Close();

            // Wait for the sort process to write the sorted text lines.
            sortProcess.WaitForExit();

            if (numOutputLines > 0)
            {
                // Write the formatted and sorted output to the console.
                Console.WriteLine(" Sort results = {0} sorted text line(s) ", 
                    numOutputLines);
                Console.WriteLine("----------");
                Console.WriteLine(sortOutput);
            }
            else 
            {
                Console.WriteLine(" No input lines were sorted.");
            }

            sortProcess.Close();
        }

        private static void SortOutputHandler(object sendingProcess, 
            DataReceivedEventArgs outLine)
        {
            // Collect the sort command output.
            if (!String.IsNullOrEmpty(outLine.Data))
            {
                numOutputLines++;
    
                // Add the text to the collected output.
                sortOutput.Append(Environment.NewLine + 
                    "[" + numOutputLines.ToString() + "] - " + outLine.Data);
            }
        }
    }
}

  • LinkDemand  for full trust for the immediate caller. This member cannot be used by partially trusted code.

Windows 98, Windows Server 2000 SP4, Windows Millennium Edition, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0
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