Process.BeginErrorReadLine Methode

public:
 void BeginErrorReadLine();

[System.Runtime.InteropServices.ComVisible(false)]
public void BeginErrorReadLine();

public void BeginErrorReadLine();

[<System.Runtime.InteropServices.ComVisible(false)>]
member this.BeginErrorReadLine : unit -> unit

member this.BeginErrorReadLine : unit -> unit

Public Sub BeginErrorReadLine ()

Kenmerken

ComVisibleAttribute

Uitzonderingen

Voorbeelden

In het volgende voorbeeld wordt de net view opdracht gebruikt om de beschikbare netwerkbronnen op een externe computer weer te geven. De gebruiker levert de naam van de doelcomputer als opdrachtregelargument. De gebruiker kan ook een bestandsnaam opgeven voor foutuitvoer. Het voorbeeld verzamelt de uitvoer van de netopdracht, wacht tot het proces is voltooid en schrijft vervolgens de uitvoerresultaten naar de console. Als de gebruiker het optionele foutenbestand levert, worden in het voorbeeld fouten naar het bestand geschreven.

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

namespace ProcessAsyncStreamSamples
{

    class ProcessNetStreamRedirection
    {
        // Define static variables shared by class methods.
        private static StreamWriter streamError =null;
        private static String netErrorFile = "";
        private static StringBuilder netOutput = null;
        private static bool errorRedirect = false;
        private static bool errorsWritten = false;

        public static void RedirectNetCommandStreams()
        {
            String netArguments;
            Process netProcess;

            // Get the input computer name.
            Console.WriteLine("Enter the computer name for the net view command:");
            netArguments = Console.ReadLine().ToUpper(CultureInfo.InvariantCulture);
            if (String.IsNullOrEmpty(netArguments))
            {
                // Default to the help command if there is not an input argument.
                netArguments = "/?";
            }

            // Check if errors should be redirected to a file.
            errorsWritten = false;
            Console.WriteLine("Enter a fully qualified path to an error log file");
            Console.WriteLine("  or just press Enter to write errors to console:");
            netErrorFile = Console.ReadLine().ToUpper(CultureInfo.InvariantCulture);
            if (!String.IsNullOrEmpty(netErrorFile))
            {
                errorRedirect = true;
            }

            // Note that at this point, netArguments and netErrorFile
            // are set with user input.  If the user did not specify
            // an error file, then errorRedirect is set to false.

            // Initialize the process and its StartInfo properties.
            netProcess = new Process();
            netProcess.StartInfo.FileName = "Net.exe";

            // Build the net command argument list.
            netProcess.StartInfo.Arguments = String.Format("view {0}",
                netArguments);

            // Set UseShellExecute to false for redirection.
            netProcess.StartInfo.UseShellExecute = false;

            // Redirect the standard output of the net command.
            // This stream is read asynchronously using an event handler.
            netProcess.StartInfo.RedirectStandardOutput = true;
            netProcess.OutputDataReceived += new DataReceivedEventHandler(NetOutputDataHandler);
            netOutput = new StringBuilder();

            if (errorRedirect)
            {
                // Redirect the error output of the net command.
                netProcess.StartInfo.RedirectStandardError = true;
                netProcess.ErrorDataReceived += new DataReceivedEventHandler(NetErrorDataHandler);
            }
            else
            {
                // Do not redirect the error output.
                netProcess.StartInfo.RedirectStandardError = false;
            }

            Console.WriteLine("\nStarting process: net {0}",
                netProcess.StartInfo.Arguments);
            if (errorRedirect)
            {
                Console.WriteLine("Errors will be written to the file {0}",
                    netErrorFile);
            }

            // Start the process.
            netProcess.Start();

            // Start the asynchronous read of the standard output stream.
            netProcess.BeginOutputReadLine();

            if (errorRedirect)
            {
                // Start the asynchronous read of the standard
                // error stream.
                netProcess.BeginErrorReadLine();
            }

            // Let the net command run, collecting the output.
            netProcess.WaitForExit();

            if (streamError != null)
            {
                // Close the error file.
                streamError.Close();
            }
            else
            {
                // Set errorsWritten to false if the stream is not
                // open.   Either there are no errors, or the error
                // file could not be opened.
                errorsWritten = false;
            }

            if (netOutput.Length > 0)
            {
                // If the process wrote more than just
                // white space, write the output to the console.
                Console.WriteLine("\nPublic network shares from net view:\n{0}\n",
                    netOutput);
            }

            if (errorsWritten)
            {
                // Signal that the error file had something
                // written to it.
                String [] errorOutput = File.ReadAllLines(netErrorFile);
                if (errorOutput.Length > 0)
                {
                    Console.WriteLine("\nThe following error output was appended to {0}.",
                        netErrorFile);
                    foreach (String errLine in errorOutput)
                    {
                        Console.WriteLine("  {0}", errLine);
                    }
                }
                Console.WriteLine();
            }

            netProcess.Close();
        }

        private static void NetOutputDataHandler(object sendingProcess,
            DataReceivedEventArgs outLine)
        {
            // Collect the net view command output.
            if (!String.IsNullOrEmpty(outLine.Data))
            {
                // Add the text to the collected output.
                netOutput.Append(Environment.NewLine + "  " + outLine.Data);
            }
        }

        private static void NetErrorDataHandler(object sendingProcess,
            DataReceivedEventArgs errLine)
        {
            // Write the error text to the file if there is something
            // to write and an error file has been specified.

            if (!String.IsNullOrEmpty(errLine.Data))
            {
                if (!errorsWritten)
                {
                    if (streamError == null)
                    {
                        // Open the file.
                        try
                        {
                            streamError = new StreamWriter(netErrorFile, true);
                        }
                        catch (Exception e)
                        {
                            Console.WriteLine("Could not open error file!");
                            Console.WriteLine(e.Message.ToString());
                        }
                    }

                    if (streamError != null)
                    {
                        // Write a header to the file if this is the first
                        // call to the error output handler.
                        streamError.WriteLine();
                        streamError.WriteLine(DateTime.Now.ToString());
                        streamError.WriteLine("Net View error output:");
                    }
                    errorsWritten = true;
                }

                if (streamError != null)
                {
                    // Write redirected errors to the file.
                    streamError.WriteLine(errLine.Data);
                    streamError.Flush();
                }
            }
        }
    }
}

// Define the namespaces used by this sample.
open System
open System.Text
open System.Globalization
open System.IO
open System.Diagnostics

// Define variables shared by functions.
let mutable streamError = Unchecked.defaultof<StreamWriter>
let mutable netErrorFile = ""
let mutable netOutput = StringBuilder()
let mutable errorRedirect = false
let mutable errorsWritten = false

let netOutputDataHandler (sendingProcess: obj) (outLine: DataReceivedEventArgs) =
    // Collect the net view command output.
    if String.IsNullOrEmpty outLine.Data |> not then
        // Add the text to the collected output.
        netOutput.Append(Environment.NewLine + "  " + outLine.Data) |> ignore

let netErrorDataHandler (sendingProcess: obj) (errLine: DataReceivedEventArgs) =
    // Write the error text to the file if there is something
    // to write and an error file has been specified.

    if String.IsNullOrEmpty errLine.Data |> not then
        if not errorsWritten then
            if isNull streamError then
                // Open the file.
                try
                    streamError <- new StreamWriter(netErrorFile, true)
                with e ->
                    printfn "Could not open error file!"
                    printfn $"{e.Message}"

            if isNull streamError |> not then
                // Write a header to the file if this is the first
                // call to the error output handler.
                streamError.WriteLine()
                streamError.WriteLine DateTime.Now
                streamError.WriteLine "Net View error output:"

            errorsWritten <- true

        if isNull streamError |> not then
            // Write redirected errors to the file.
            streamError.WriteLine errLine.Data
            streamError.Flush()


let redirectNetCommandStreams () =
    // Get the input computer name.
    printfn "Enter the computer name for the net view command:"
    let netArguments = stdin.ReadLine().ToUpper CultureInfo.InvariantCulture
    // Default to the help command if there is not an input argument.
    let netArguments =
        if String.IsNullOrEmpty netArguments then
            "/?"
        else
            netArguments

    // Check if errors should be redirected to a file.
    errorsWritten <- false
    printfn "Enter a fully qualified path to an error log file"
    printfn "  or just press Enter to write errors to console:"
    netErrorFile <- stdin.ReadLine().ToUpper CultureInfo.InvariantCulture

    if String.IsNullOrEmpty netErrorFile |> not then
        errorRedirect <- true

    // Note that at this point, netArguments and netErrorFile
    // are set with user input.  If the user did not specify
    // an error file, then errorRedirect is set to false.

    // Initialize the process and its StartInfo properties.
    let netProcess = new Process()
    netProcess.StartInfo.FileName <- "Net.exe"

    // Build the net command argument list.
    netProcess.StartInfo.Arguments <- $"view {netArguments}"

    // Set UseShellExecute to false for redirection.
    netProcess.StartInfo.UseShellExecute <- false

    // Redirect the standard output of the net command.
    // This stream is read asynchronously using an event handler.
    netProcess.StartInfo.RedirectStandardOutput <- true
    netProcess.OutputDataReceived.AddHandler(DataReceivedEventHandler netOutputDataHandler)
    netOutput <- new StringBuilder()

    if errorRedirect then
        // Redirect the error output of the net command.
        netProcess.StartInfo.RedirectStandardError <- true
        netProcess.ErrorDataReceived.AddHandler(DataReceivedEventHandler netErrorDataHandler)
    else
        // Do not redirect the error output.
        netProcess.StartInfo.RedirectStandardError <- false

    printfn $"\nStarting process: net {netProcess.StartInfo.Arguments}"

    if errorRedirect then
        printfn $"Errors will be written to the file {netErrorFile}"

    // Start the process.
    netProcess.Start() |> ignore

    // Start the asynchronous read of the standard output stream.
    netProcess.BeginOutputReadLine()

    if errorRedirect then
        // Start the asynchronous read of the standard error stream.
        netProcess.BeginErrorReadLine()

    // Let the net command run, collecting the output.
    netProcess.WaitForExit()

    if streamError <> null then
        // Close the error file.
        streamError.Close()
    else
        // Set errorsWritten to false if the stream is not
        // open.   Either there are no errors, or the error
        // file could not be opened.
        errorsWritten <- false

    if netOutput.Length > 0 then
        // If the process wrote more than just
        // white space, write the output to the console.
        printfn $"\nPublic network shares from net view:\n{netOutput}\n"

    if errorsWritten then
        // Signal that the error file had something
        // written to it.
        let errorOutput = File.ReadAllLines netErrorFile

        if errorOutput.Length > 0 then
            printfn $"\nThe following error output was appended to {netErrorFile}."

            for errLine in errorOutput do
                printfn $"  {errLine}"

        printfn ""

    netProcess.Close()

' Define the namespaces used by this sample.
Imports System.Text
Imports System.Globalization
Imports System.IO
Imports System.Diagnostics
Imports System.Threading
Imports System.ComponentModel

Namespace ProcessAsyncStreamSamples
   
   Class ProcessAsyncErrorRedirection
      ' Define static variables shared by class methods.
      Private Shared streamError As StreamWriter = Nothing
      Private Shared netErrorFile As String = ""
      Private Shared netOutput As StringBuilder = Nothing
      Private Shared errorRedirect As Boolean = False
      Private Shared errorsWritten As Boolean = False
      
      Public Shared Sub RedirectNetCommandStreams()
         Dim netArguments As String
         Dim netProcess As Process
         
         ' Get the input computer name.
         Console.WriteLine("Enter the computer name for the net view command:")
         netArguments = Console.ReadLine().ToUpper(CultureInfo.InvariantCulture)
         If String.IsNullOrEmpty(netArguments) Then
            ' Default to the help command if there is 
            ' not an input argument.
            netArguments = "/?"
         End If
         
         ' Check if errors should be redirected to a file.
         errorsWritten = False
         Console.WriteLine("Enter a fully qualified path to an error log file")
         Console.WriteLine("  or just press Enter to write errors to console:")
         netErrorFile = Console.ReadLine().ToUpper(CultureInfo.InvariantCulture)
         If Not String.IsNullOrEmpty(netErrorFile) Then
            errorRedirect = True
         End If
         
         ' Note that at this point, netArguments and netErrorFile
         ' are set with user input.  If the user did not specify
         ' an error file, then errorRedirect is set to false.

         ' Initialize the process and its StartInfo properties.
         netProcess = New Process()
         netProcess.StartInfo.FileName = "Net.exe"
         
         ' Build the net command argument list.
         netProcess.StartInfo.Arguments = String.Format("view {0}", _
                                                        netArguments)
         
         ' Set UseShellExecute to false for redirection.
         netProcess.StartInfo.UseShellExecute = False
         
         ' Redirect the standard output of the net command.  
         ' Read the stream asynchronously using an event handler.
         netProcess.StartInfo.RedirectStandardOutput = True
         AddHandler netProcess.OutputDataReceived, _
                            AddressOf NetOutputDataHandler
         netOutput = new StringBuilder()
         
         If errorRedirect Then
            ' Redirect the error output of the net command. 
            netProcess.StartInfo.RedirectStandardError = True
            AddHandler netProcess.ErrorDataReceived, _
                            AddressOf NetErrorDataHandler
         Else
            ' Do not redirect the error output.
            netProcess.StartInfo.RedirectStandardError = False
         End If
         
         Console.WriteLine(ControlChars.Lf + "Starting process: NET {0}", _
                           netProcess.StartInfo.Arguments)
         If errorRedirect Then
            Console.WriteLine("Errors will be written to the file {0}", _
                           netErrorFile)
         End If
         
         ' Start the process.
         netProcess.Start()
         
         ' Start the asynchronous read of the standard output stream.
         netProcess.BeginOutputReadLine()
         
         If errorRedirect Then
            ' Start the asynchronous read of the standard
            ' error stream.
            netProcess.BeginErrorReadLine()
         End If
         
         ' Let the net command run, collecting the output.
         netProcess.WaitForExit()
      
         If Not streamError Is Nothing Then
             ' Close the error file.
             streamError.Close()
         Else 
             ' Set errorsWritten to false if the stream is not
             ' open.   Either there are no errors, or the error
             ' file could not be opened.
             errorsWritten = False
         End If
   
         If netOutput.Length > 0 Then
            ' If the process wrote more than just
            ' white space, write the output to the console.
            Console.WriteLine()
            Console.WriteLine("Public network shares from net view:")
            Console.WriteLine()
            Console.WriteLine(netOutput)
            Console.WriteLine()
         End If
         
         If errorsWritten Then
            ' Signal that the error file had something 
            ' written to it.
            Dim errorOutput As String()
            errorOutput = File.ReadAllLines(netErrorFile)
            If errorOutput.Length > 0 Then

                Console.WriteLine(ControlChars.Lf + _
                    "The following error output was appended to {0}.", _
                    netErrorFile)
                Dim errLine as String
                For Each errLine in errorOutput
                    Console.WriteLine("  {0}", errLine)
                Next
          
                Console.WriteLine()
            End If
         End If
         
         netProcess.Close()
      End Sub 
      
      
      Private Shared Sub NetOutputDataHandler(sendingProcess As Object, _
          outLine As DataReceivedEventArgs)

         ' Collect the net view command output.
         If Not String.IsNullOrEmpty(outLine.Data) Then
            ' Add the text to the collected output.
            netOutput.Append(Environment.NewLine + "  " + outLine.Data)
         End If
      End Sub 
       
      
      Private Shared Sub NetErrorDataHandler(sendingProcess As Object, _
          errLine As DataReceivedEventArgs)

         ' Write the error text to the file if there is something to
         ' write and an error file has been specified.

         If Not String.IsNullOrEmpty(errLine.Data) Then

            If Not errorsWritten Then
                If streamError Is Nothing Then
                    ' Open the file.
                    Try 
                        streamError = New StreamWriter(netErrorFile, true)
                    Catch e As Exception
                        Console.WriteLine("Could not open error file!")
                        Console.WriteLine(e.Message.ToString())
                    End Try
                End If

                If Not streamError Is Nothing Then

                    ' Write a header to the file if this is the first
                    ' call to the error output handler.
                    streamError.WriteLine()
                    streamError.WriteLine(DateTime.Now.ToString())
                    streamError.WriteLine("Net View error output:")

                End If

                errorsWritten = True
            End If
                     
            If Not streamError Is Nothing Then
                  
                ' Write redirected errors to the file.
                streamError.WriteLine(errLine.Data)
                streamError.Flush()
             End If
          End If
      End Sub 
   End Class  
End Namespace

Opmerkingen

De StandardError stream kan synchroon of asynchroon worden gelezen. Methoden zoals Read, ReadLineen ReadToEnd voeren synchrone leesbewerkingen uit op de foutuitvoerstroom van het proces. Deze synchrone leesbewerkingen worden pas voltooid als de bijbehorende Process schrijfbewerkingen naar StandardError de stream zijn voltooid of de stream worden gesloten.

Start daarentegen BeginErrorReadLine asynchrone leesbewerkingen op de StandardError stream. Met deze methode kunt u de aangewezen gebeurtenis-handler voor de stroomuitvoer inschakelen en onmiddellijk terugkeren naar de aanroeper, die ander werk kan uitvoeren terwijl de stroomuitvoer wordt omgeleid naar de gebeurtenis-handler.

Volg deze stappen om asynchrone leesbewerkingen StandardError uit te voeren voor een Process :

1. Stel UseShellExecute in op false.

2. Stel RedirectStandardError in op true.

3. Voeg uw gebeurtenis-handler toe aan de ErrorDataReceived gebeurtenis. De gebeurtenis-handler moet overeenkomen met de handtekening van de System.Diagnostics.DataReceivedEventHandler gemachtigde.

4. Start de Process.

5. Bel BeginErrorReadLine naar de Process. Met deze aanroep worden asynchrone leesbewerkingen gestart op StandardError.

Wanneer asynchrone leesbewerkingen worden gestart, wordt de gebeurtenis-handler telkens aangeroepen wanneer de bijbehorende Process tekstregel naar StandardError de stroom schrijft.

U kunt een asynchrone leesbewerking annuleren door aan te roepen CancelErrorRead. De leesbewerking kan worden geannuleerd door de beller of door de gebeurtenis-handler. Na het annuleren kunt u opnieuw bellen BeginErrorReadLine om asynchrone leesbewerkingen te hervatten.

Zie ook

• RedirectStandardError
• StandardError
• ErrorDataReceived
• DataReceivedEventHandler
• CancelErrorRead()