File Class (System.IO)

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.NET Framework Class Library

File Class

Updated: November 2007

Provides static methods for the creation, copying, deletion, moving, and opening of files, and aids in the creation of FileStream objects.

Namespace: System.IO
Assembly: mscorlib (in mscorlib.dll)

Syntax

Visual Basic (Declaration)

<ComVisibleAttribute(True)> _
Public NotInheritable Class File

Visual Basic (Usage)

You do not need to declare an instance of a static class in order to access its members.

[ComVisibleAttribute(true)]
public static class File

Visual C++

[ComVisibleAttribute(true)]
public ref class File abstract sealed

/** @attribute ComVisibleAttribute(true) */
public final class File

JScript

public final class File

Remarks

Use the File class for typical operations such as copying, moving, renaming, creating, opening, deleting, and appending to files. You can also use the File class to get and set file attributes or DateTime information related to the creation, access, and writing of a file.

Many of the File methods return other I/O types when you create or open files. You can use these other types to further manipulate a file. For more information, see specific File members such as OpenText, CreateText, or Create.

Because all File methods are static, it might be more efficient to use a File method rather than a corresponding FileInfo instance method if you want to perform only one action. All File methods require the path to the file that you are manipulating.

The static methods of the File class perform security checks on all methods. If you are going to reuse an object several times, consider using the corresponding instance method of FileInfo instead, because the security check will not always be necessary.

By default, full read/write access to new files is granted to all users.

The following table describes the enumerations that are used to customize the behavior of various File methods.

Enumeration	Description
FileAccess	Specifies read and write access to a file.
FileShare	Specifies the level of access permitted for a file that is already in use.
FileMode	Specifies whether the contents of an existing file are preserved or overwritten, and whether requests to create an existing file cause an exception.

Note:
In members that accept a path as an input string, that path must be well-formed or an exception is raised. For example, if a path is fully qualified but begins with a space, the path is not trimmed in methods of the class. Therefore, the path is malformed and an exception is raised. Similarly, a path or a combination of paths cannot be fully qualified twice. For example, "c:\temp c:\windows" also raises an exception in most cases. Ensure that your paths are well-formed when using methods that accept a path string.

Note:

In members that accept a path as an input string, that path must be well-formed or an exception is raised. For example, if a path is fully qualified but begins with a space, the path is not trimmed in methods of the class. Therefore, the path is malformed and an exception is raised. Similarly, a path or a combination of paths cannot be fully qualified twice. For example, "c:\temp c:\windows" also raises an exception in most cases. Ensure that your paths are well-formed when using methods that accept a path string.

In members that accept a path, the path can refer to a file or just a directory. The specified path can also refer to a relative path or a Universal Naming Convention (UNC) path for a server and share name. For example, all the following are acceptable paths:

"c:\\MyDir\\MyFile.txt" in C#, or "c:\MyDir\MyFile.txt" in Visual Basic.
"c:\\MyDir" in C#, or "c:\MyDir" in Visual Basic.
"MyDir\\MySubdir" in C#, or "MyDir\MySubDir" in Visual Basic.
"\\\\MyServer\\MyShare" in C#, or "\\MyServer\MyShare" in Visual Basic.

For a list of common I/O tasks, see Common I/O Tasks.

Examples

The following example demonstrates some of the main members of the File class.

Visual Basic

Imports System
Imports System.IO

Public Class Test
    Public Shared Sub Main()
        Dim path As String = "c:\temp\MyTest.txt"
        If File.Exists(path) = False Then
            ' Create a file to write to.
            Dim sw As StreamWriter = File.CreateText(path)
            sw.WriteLine("Hello")
            sw.WriteLine("And")
            sw.WriteLine("Welcome")
            sw.Flush()
            sw.Close()
        End If

        Try
            ' Open the file to read from.
            Dim sr As StreamReader = File.OpenText(path)
            Do While sr.Peek() >= 0
                Console.WriteLine(sr.ReadLine())
            Loop
            sr.Close()
            Dim path2 As String = path + "temp"

            ' Ensure that the target does not exist.
            File.Delete(path2)

            ' Copy the file.
            File.Copy(path, path2)
            Console.WriteLine("{0} was copied to {1}.", path, path2)

            ' Delete the newly created file.
            File.Delete(path2)
            Console.WriteLine("{0} was successfully deleted.", path2)

        Catch e As Exception
            Console.WriteLine("The process failed: {0}", e.ToString())
        End Try
    End Sub
End Class

using System;
using System.IO;

class Test 
{
    public static void Main() 
    {
        string path = @"c:\temp\MyTest.txt";
        if (!File.Exists(path)) 
        {
            // Create a file to write to.
            using (StreamWriter sw = File.CreateText(path)) 
            {
                sw.WriteLine("Hello");
                sw.WriteLine("And");
                sw.WriteLine("Welcome");
            }    
        }

        // Open the file to read from.
        using (StreamReader sr = File.OpenText(path)) 
        {
            string s = "";
            while ((s = sr.ReadLine()) != null) 
            {
                Console.WriteLine(s);
            }
        }

        try 
        {
            string path2 = path + "temp";
            // Ensure that the target does not exist.
            File.Delete(path2);

            // Copy the file.
            File.Copy(path, path2);
            Console.WriteLine("{0} was copied to {1}.", path, path2);

            // Delete the newly created file.
            File.Delete(path2);
            Console.WriteLine("{0} was successfully deleted.", path2);
        } 
        catch (Exception e) 
        {
            Console.WriteLine("The process failed: {0}", e.ToString());
        }
    }
}

Visual C++

using namespace System;
using namespace System::IO;
int main()
{
   String^ path = "c:\\temp\\MyTest.txt";
   if (  !File::Exists( path ) )
   {

      // Create a file to write to.
      StreamWriter^ sw = File::CreateText( path );
      try
      {
         sw->WriteLine( "Hello" );
         sw->WriteLine( "And" );
         sw->WriteLine( "Welcome" );
      }
      finally
      {
         if ( sw )
                  delete (IDisposable^)(sw);
      }
   }

   // Open the file to read from.
   StreamReader^ sr = File::OpenText( path );
   try
   {
      String^ s = "";
      while ( s = sr->ReadLine() )
      {
         Console::WriteLine( s );
      }
   }
   finally
   {
      if ( sr )
            delete (IDisposable^)(sr);
   }

   try
   {
      String^ path2 = String::Concat( path, "temp" );

      // Ensure that the target does not exist.
      File::Delete( path2 );

      // Copy the file.
      File::Copy( path, path2 );
      Console::WriteLine( "{0} was copied to {1}.", path, path2 );

      // Delete the newly created file.
      File::Delete( path2 );
      Console::WriteLine( "{0} was successfully deleted.", path2 );
   }
   catch ( Exception^ e ) 
   {
      Console::WriteLine( "The process failed: {0}", e );
   }
}

import System.*;
import System.IO.*;

class Test
{
    public static void main(String[] args)
    {
        String path = "c:\\temp\\MyTest.txt";

        if (!(File.Exists(path))) {
            // Create a file to write to.
            StreamWriter sw = File.CreateText(path);

            try {
                sw.WriteLine("Hello");
                sw.WriteLine("And");
                sw.WriteLine("Welcome");
            }
            finally {
                sw.Dispose();
            }
        }

        // Open the file to read from.
        StreamReader sr = File.OpenText(path);

        try {
            String s = "";

            while ((s = sr.ReadLine()) != null) {
                Console.WriteLine(s);
            }
        }
        finally {
            sr.Dispose();
        }
        try {
            String path2 = path + "temp";

            // Ensure that the target does not exist.
            File.Delete(path2);

            // Copy the file.
            File.Copy(path, path2);
            Console.WriteLine("{0} was copied to {1}.", path, path2);

            // Delete the newly created file.
            File.Delete(path2);
            Console.WriteLine("{0} was successfully deleted.", path2);
        }
        catch (System.Exception e) {
            Console.WriteLine("The process failed: {0}", e.ToString());
        }
    } //main
} //Test

Inheritance Hierarchy

System..::.Object
System.IO..::.File

Thread Safety

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Platforms

Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

Version Information