방법: 파일에 텍스트 쓰기How to: Write text to a file

이 항목에서는 .NET 앱의 파일에 텍스트를 작성하는 다양한 방법을 보여줍니다.This topic shows different ways to write text to a file for a .NET app.

파일에 텍스트를 쓸 때는 일반적으로 다음 클래스 및 메서드가 사용됩니다.The following classes and methods are typically used to write text to a file:

참고

다음 예제에서는 필요한 최소 코드 양만 보여줍니다.The following examples show only the minimum amount of code needed. 실제 앱은 일반적으로 더 강력한 오류 검사 및 예외 처리 기능을 제공합니다.A real-world app usually provides more robust error checking and exception handling.

예제: StreamWriter를 사용하여 텍스트를 동기식으로 쓰기Example: Synchronously write text with StreamWriter

다음 예제에서는 StreamWriter 클래스를 사용하여 한 번에 한 줄씩 새 파일에 텍스트를 동기식으로 쓰는 방법을 보여줍니다.The following example shows how to use the StreamWriter class to synchronously write text to a new file one line at a time. StreamWriter 개체는 using 문에서 선언되고 인스턴스화되므로 스트림을 자동으로 플러시하고 닫는 Dispose 메서드가 호출됩니다.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

예제: StreamWriter를 사용하여 텍스트를 동기식으로 추가Example: Synchronously append text with StreamWriter

다음 예제에서는 StreamWriter 클래스를 사용하여 첫 번째 예제에서 만든 텍스트 파일에 텍스트를 동기식으로 추가하는 방법을 보여줍니다.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

예제: StreamWriter를 사용하여 텍스트를 비동기식으로 쓰기Example: Asynchronously write text with StreamWriter

다음 예제에서는 StreamWriter 클래스를 사용하여 새 파일에 비동기적으로 텍스트를 쓰는 방법을 보여 줍니다.The following example shows how to asynchronously write text to a new file using the StreamWriter class. WriteAsync 메서드를 호출하려면 메서드 호출이 async 메서드 내에 있어야 합니다.To invoke the WriteAsync method, the method call must be within an async method. C# 예제에는 C# 7.1 이상이 필요하며, 이 경우 프로그램 진입점에서 async 한정자에 대한 지원이 추가됩니다.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.

예제: 파일 클래스로 텍스트 쓰기 및 추가Example: Write and append text with the File class

다음 예제에서는 File 클래스를 사용하여 새 파일에 텍스트를 쓰고 동일한 파일에 새 텍스트 줄을 추가하는 방법을 보여 줍니다.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. WriteAllTextAppendAllLines 메서드는 자동으로 파일을 열고 닫습니다.The WriteAllText and AppendAllLines methods open and close the file automatically. WriteAllText 메서드에 제공한 경로가 이미 있는 경우 파일을 덮어씁니다.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

참고 항목See also