Procedura: Aprire un file di log e accodare informazioniHow to: Open and append to a log file

StreamWriter e StreamReader scrivono e leggono i caratteri nei flussi.StreamWriter and StreamReader write characters to and read characters from streams. L'esempio di codice seguente apre il file log.txt per l'input oppure crea il file, se non esiste già, e aggiunge informazioni alla fine del file.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. Nell'esempio, il contenuto del file viene quindi scritto nell'output standard per la visualizzazione.The example then writes the contents of the file to standard output for display.

In alternativa a questo esempio, è possibile archiviare le informazioni come un'unica stringa o matrice di stringhe e usare il metodo File.WriteAllText o File.WriteAllLines per ottenere la stessa funzionalità.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

Gli utenti di Visual Basic possono scegliere di usare i metodi e le proprietà forniti dalla classe Log o dalla classe FileSystem per creare file di log o scrivere al loro interno.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.

EsempioExample

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.

Vedere ancheSee also