Procedura: Scrivere testo in un fileHow to: Write text to a file

  • 3 minuti per la lettura
  • Autori di contributi
    • Maira Wenzel
    • olprod
    • yishengjin1413

Questo argomento illustra diversi modi per scrivere testo in un file per un'app .NET.This topic shows different ways to write text to a file for a .NET app.

Per scrivere un testo in un file vengono in genere usati le classi e i metodi seguenti:The following classes and methods are typically used to write text to a file:

Nota

Gli esempi seguenti visualizzano solo la quantità minima di codice necessario.The following examples show only the minimum amount of code needed. Un'applicazione reale include in genere procedure di controllo degli errori e di gestione delle eccezioni più efficaci.A real-world app usually provides more robust error checking and exception handling.

Esempio: Scrivere testo in modo sincrono con StreamWriterExample: Synchronously write text with StreamWriter

L'esempio seguente illustra come usare la classe StreamWriter per scrivere un testo in modo sincrono una riga alla volta in un nuovo file.The following example shows how to use the StreamWriter class to synchronously write text to a new file one line at a time. Poiché l'oggetto StreamWriter viene dichiarato in un'istruzione using in cui viene creata anche un'istanza dell'oggetto stesso, viene chiamato il metodo Dispose che scarica e chiude automaticamente il flusso.Because the StreamWriter object is declared and instantiated in a using statement, the Dispose method is invoked, which automatically flushes and closes the stream.

using System;
using System.IO;

class Program
{
    static void Main(string[] args)
    {
    
        // Create a string array with the lines of text
        string[] lines = { "First line", "Second line", "Third line" };

        // Set a variable to the Documents path.
        string docPath =
          Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments);

        // Write the string array to a new file named "WriteLines.txt".
        using (StreamWriter outputFile = new StreamWriter(Path.Combine(docPath, "WriteLines.txt")))
        {
            foreach (string line in lines)
                outputFile.WriteLine(line);
        }
    }
}
// The example creates a file named "WriteLines.txt" with the following contents:
// First line
// Second line
// Third line

Imports System.IO

Class WriteText

    Public Shared Sub Main()

        ' Create a string array with the lines of text
        Dim lines() As String = {"First line", "Second line", "Third line"}

        ' Set a variable to the Documents path.
        Dim docPath As String = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments)

        ' Write the string array to a new file named "WriteLines.txt".
        Using outputFile As New StreamWriter(Path.Combine(docPath, Convert.ToString("WriteLines.txt")))
            For Each line As String In lines
                outputFile.WriteLine(line)
            Next
        End Using

    End Sub

End Class

' The example creates a file named "WriteLines.txt" with the following contents:
' First line
' Second line
' Third line

Esempio: Accodare testo in modo sincrono con StreamWriterExample: Synchronously append text with StreamWriter

L'esempio seguente illustra come usare la classe StreamWriter per accodare testo in modo sincrono al file di testo creato nel primo esempio.The following example shows how to use the StreamWriter class to synchronously append text to the text file created in the first example.

using System;
using System.IO;

class Program
{
    static void Main(string[] args)
    {

        // Set a variable to the Documents path.
        string docPath = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments);

        // Append text to an existing file named "WriteLines.txt".
        using (StreamWriter outputFile = new StreamWriter(Path.Combine(docPath, "WriteLines.txt"), true))
        {
            outputFile.WriteLine("Fourth Line");
        }
    }
}
// The example adds the following line to the contents of "WriteLines.txt":
// Fourth Line

Imports System.IO

Class AppendText

    Public Shared Sub Main()

        ' Set a variable to the Documents path.
        Dim docPath As String =
            Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments)

        ' Append text to an existing file named "WriteLines.txt".
        Using outputFile As New StreamWriter(Path.Combine(docPath, Convert.ToString("WriteLines.txt")), True)
            outputFile.WriteLine("Fourth Line")
        End Using

    End Sub

End Class

' The example adds the following line to the contents of "WriteLines.txt":
' Fourth Line

Esempio: Scrivere testo in modo asincrono con StreamWriterExample: Asynchronously write text with StreamWriter

L'esempio seguente illustra come scrivere in modo asincrono un testo in un nuovo file usando la classe StreamWriter .The following example shows how to asynchronously write text to a new file using the StreamWriter class. Per chiamare il metodo WriteAsync, la chiamata al metodo deve essere inclusa in un metodo async.To invoke the WriteAsync method, the method call must be within an async method. L'esempio C# richiede C# 7.1 o versioni successive, che aggiunge il supporto per il modificatore async nel punto di ingresso del programma.The C# example requires C# 7.1 or later, which adds support for the async modifier on the program entry point.

using System;
using System.IO;
using System.Threading.Tasks;

class Program
{
    static async Task Main()
    {
        // Set a variable to the Documents path.
        string docPath = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments);

        // Write the specified text asynchronously to a new file named "WriteTextAsync.txt".
        using (StreamWriter outputFile = new StreamWriter(Path.Combine(docPath, "WriteTextAsync.txt")))
        {
            await outputFile.WriteAsync("This is a sentence.");
        }
    }
}
// The example creates a file named "WriteTextAsync.txt" with the following contents:
// This is a sentence.

Imports System.IO

Public Module Example
    Public Sub Main()
        WriteTextAsync()
    End Sub

    Async Sub WriteTextAsync()
        ' Set a variable to the Documents path.
        Dim docPath As String = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments)

        ' Write the text asynchronously to a new file named "WriteTextAsync.txt".
        Using outputFile As New StreamWriter(Path.Combine(docPath, Convert.ToString("WriteTextAsync.txt")))
            Await outputFile.WriteAsync("This is a sentence.")
        End Using
    End Sub
End Module

' The example creates a file named "WriteTextAsync.txt" with the following contents:
' This is a sentence.

Esempio: Scrivere e accodare testo con la classe FileExample: Write and append text with the File class

L'esempio seguente illustra come scrivere un testo in un nuovo file e aggiungere nuove righe di testo nello stesso file usando la classe File .The following example shows how to write text to a new file and append new lines of text to the same file using the File class. I metodi WriteAllText e AppendAllLines aprono e chiudono automaticamente il file.The WriteAllText and AppendAllLines methods open and close the file automatically. Se il percorso specificato per il metodo WriteAllText esiste già, il file viene sovrascritto.If the path you provide to the WriteAllText method already exists, the file is overwritten.

using System;
using System.IO;

class Program
{
    static void Main(string[] args)
    {
        // Create a string with a line of text.
        string text = "First line" + Environment.NewLine;

        // Set a variable to the Documents path.
        string docPath = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments);

        // Write the text to a new file named "WriteFile.txt".
        File.WriteAllText(Path.Combine(docPath, "WriteFile.txt"), text);

        // Create a string array with the additional lines of text
        string[] lines = { "New line 1", "New line 2" };

        // Append new lines of text to the file
        File.AppendAllLines(Path.Combine(docPath, "WriteFile.txt"), lines);
    }
}
// The example creates a file named "WriteFile.txt" with the contents:
// First line
// And then appends the following contents:
// New line 1
// New line 2

Imports System.IO

Class WriteFile

    Public Shared Sub Main()

        ' Create a string array with the lines of text
        Dim text As String = "First line" & Environment.NewLine

        ' Set a variable to the Documents path.
        Dim docPath As String = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments)

        ' Write the text to a new file named "WriteFile.txt".
        File.WriteAllText(Path.Combine(docPath, Convert.ToString("WriteFile.txt")), text)

        ' Create a string array with the additional lines of text
        Dim lines() As String = {"New line 1", "New line 2"}

        ' Append new lines of text to the file
        File.AppendAllLines(Path.Combine(docPath, Convert.ToString("WriteFile.txt")), lines)

    End Sub

End Class

' The example creates a file named "WriteFile.txt" with the following contents:
' First line
' And then appends the following contents:
' New line 1
' New line 2

Vedere ancheSee also