Postupy: Zápis textu do souboruHow to: Write text to a file

Toto téma ukazuje různé způsoby zápisu textu do souborů pro aplikace .NET.This topic shows different ways to write text to a file for a .NET app.

Následující třídy a metody se obvykle používají k zápisu textu do souboru:The following classes and methods are typically used to write text to a file:

Poznámka

Následující příklady ukazují jenom minimální množství kódu, které jsou potřeba.The following examples show only the minimum amount of code needed. Reálné aplikace obvykle poskytuje robustnější kontroly chyb a zpracování výjimek.A real-world app usually provides more robust error checking and exception handling.

Příklad: Synchronně napsat text pomocí třídy StreamWriterExample: Synchronously write text with StreamWriter

Následující příklad ukazuje způsob použití StreamWriter tříd synchronně zápisu textu na nový řádek jeden soubor současně.The following example shows how to use the StreamWriter class to synchronously write text to a new file one line at a time. Protože StreamWriter objekt je deklarovaný a instance v using příkaz, Dispose je vyvolána metoda, která automaticky vyprázdní a zavře datový proud.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

Příklad: Synchronně připojit text pomocí třídy StreamWriterExample: Synchronously append text with StreamWriter

Následující příklad ukazuje způsob použití StreamWriter tříd synchronně přidat text do textového souboru vytvořeného v prvním příkladu.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

Příklad: Asynchronně napsat text pomocí třídy StreamWriterExample: Asynchronously write text with StreamWriter

Následující příklad ukazuje způsob asynchronního zápisu textu do nového souboru pomocí StreamWriter třídy.The following example shows how to asynchronously write text to a new file using the StreamWriter class. K vyvolání WriteAsync metody volání metody, které musí být v rámci async metody.To invoke the WriteAsync method, the method call must be within an async method. C# Příklad vyžaduje C# 7.1 nebo novější, který přidává podporu pro async modifikátor na vstupní bod programu.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.

Příklad: Zapsat a připojit text pomocí třídy souboruExample: Write and append text with the File class

Následující příklad ukazuje, jak zápis textu do nového souboru a přidávat nové řádky textu do stejného souboru pomocí File třídy.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. WriteAllText a AppendAllLines metod otevřete a zavřete soubor automaticky.The WriteAllText and AppendAllLines methods open and close the file automatically. Pokud cesta poskytnete WriteAllText metoda již existuje, přepíše se.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

Viz také:See also