DataReceivedEventHandler 委托

定义

命名空间:

System.Diagnostics

程序集:

System.Diagnostics.Process.dll

表示将处理 OutputDataReceived 的 ErrorDataReceived 事件或 Process 事件的方法。

C#

public delegate void DataReceivedEventHandler(object sender, DataReceivedEventArgs e);

参数

sender

Object

事件源。

e

DataReceivedEventArgs

包含事件数据的 DataReceivedEventArgs。

示例

下面的代码示例演示如何对 sort 命令的重定向StandardOutput流执行异步读取操作。 sort 命令是一个控制台应用程序，用于读取文本输入并对其进行排序。

该示例为事件处理程序创建委托 DataReceivedEventHandler ， SortOutputHandler 并将委托与 OutputDataReceived 事件关联。 事件处理程序从重定向 StandardOutput 的流接收文本行，设置文本格式，并将文本写入屏幕。

C#

// 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 = 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 += 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 = {numOutputLines} sorted text line(s) ");
                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}] - {outLine.Data}");
            }
        }
    }
}

namespace ProcessAsyncStreamSamples
{

    class ProcessSampleMain
    {
        /// The main entry point for the application.
        static void Main()
        {
            try
            {
                SortOutputRedirection.SortInputListText();
            }
            catch (InvalidOperationException e)
            {
                Console.WriteLine("Exception:");
                Console.WriteLine(e);
            }
        }
    }
}

注解

创建 DataReceivedEventHandler 委托时，需要标识将处理该事件的方法。 若要将事件与事件处理程序关联，请将该委托的一个实例添加到事件中。 除非移除了该委托，否则每当发生该事件时就会调用事件处理程序。 有关事件处理程序委托的详细信息，请参阅 处理和引发事件。

若要异步收集进程的重定向 StandardOutput 或 StandardError 流输出，请将事件处理程序添加到 OutputDataReceived 或 ErrorDataReceived 事件。 每次进程将行写入相应的重定向流时，都会引发这些事件。 当重定向的流关闭时，会将空行发送到事件处理程序。 在访问 Data 属性之前，请确保事件处理程序检查此条件。 例如，可以使用 static 方法 String.IsNullOrEmpty 验证 Data 事件处理程序中的 属性。

扩展方法

GetMethodInfo(Delegate)

获取指示指定委托表示的方法的对象。

适用于

另请参阅

• DataReceivedEventArgs
• OutputDataReceived
• ErrorDataReceived
• Process