Filtrar Abrir y anexar a un archivo de registroHow to: Open and append to a log file

StreamWriter y StreamReader escriben y leen caracteres de secuencias.StreamWriter and StreamReader write characters to and read characters from streams. En el siguiente ejemplo de código se abre el archivo log.txt para realizar entradas o se crea el archivo en caso de que no exista y se adjunta información de registro al final del archivo.The following code example opens the log.txt file for input, or creates it if it doesn't exist, and appends log information to the end of the file. El ejemplo, a continuación, escribe el contenido del archivo en la salida estándar para su presentación.The example then writes the contents of the file to standard output for display.

Como alternativa a este ejemplo, podría almacenar la información como una sola cadena o como una matriz de cadenas, y usar el método File.WriteAllText o File.WriteAllLines para lograr la misma funcionalidad.As an alternative to this example, you could store the information as a single string or string array, and use the File.WriteAllText or File.WriteAllLines method to achieve the same functionality.

Nota

Los usuarios de Visual Basic tienen la opción de utilizar los métodos y las propiedades proporcionados por las clases Log o FileSystem para crear archivos de registro o escribir en ellos.Visual Basic users may choose to use the methods and properties provided by the Log class or FileSystem class for creating or writing to log files.

EjemploExample

using System;
using System.IO;

class DirAppend
{
    public static void Main()
    {
        using (StreamWriter w = File.AppendText("log.txt"))
        {
            Log("Test1", w);
            Log("Test2", w);
        }
        
        using (StreamReader r = File.OpenText("log.txt"))
        {
            DumpLog(r);
        }
    }

    public static void Log(string logMessage, TextWriter w)
    {
        w.Write("\r\nLog Entry : ");
        w.WriteLine($"{DateTime.Now.ToLongTimeString()} {DateTime.Now.ToLongDateString()}");
        w.WriteLine("  :");
        w.WriteLine($"  :{logMessage}");
        w.WriteLine ("-------------------------------");
    }

    public static void DumpLog(StreamReader r)
    {
        string line;
        while ((line = r.ReadLine()) != null)
        {
            Console.WriteLine(line);
        }
    }
}
// The example creates a file named "log.txt" and writes the following lines to it,
// or appends them to the existing "log.txt" file:

// Log Entry : <current long time string> <current long date string>
//  :
//  :Test1
// -------------------------------

// Log Entry : <current long time string> <current long date string>
//  :
//  :Test2
// -------------------------------

// It then writes the contents of "log.txt" to the console.
Imports System.IO

Class DirAppend
    Public Shared Sub Main()
        Using w As StreamWriter = File.AppendText("log.txt")
            Log("Test1", w)
            Log("Test2", w)
        End Using

        Using r As StreamReader = File.OpenText("log.txt")
            DumpLog(r)
        End Using
    End Sub

    Public Shared Sub Log(logMessage As String, w As TextWriter)
        w.Write(vbCrLf + "Log Entry : ")
        w.WriteLine($"{DateTime.Now.ToLongTimeString()} {DateTime.Now.ToLongDateString()}")
        w.WriteLine("  :")
        w.WriteLine($"  :{logMessage}")
        w.WriteLine ("-------------------------------")
    End Sub

    Public Shared Sub DumpLog(r As StreamReader)
        Dim line As String
        line = r.ReadLine()
        While Not (line Is Nothing)
            Console.WriteLine(line)
            line = r.ReadLine()
        End While
    End Sub
End Class

' The example creates a file named "log.txt" and writes the following lines to it,
' or appends them to the existing "log.txt" file:

' Log Entry : <current long time string> <current long date string>
'  :
'  :Test1
' -------------------------------

' Log Entry : <current long time string> <current long date string>
'  :
'  :Test2
' -------------------------------

' It then writes the contents of "log.txt" to the console.

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