Windows Dev Center

Information
The topic you requested is included in another documentation set. For convenience, it's displayed below. Choose Switch to see the topic in its original location.

File.OpenWrite Method

Opens an existing file for writing.

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

public static FileStream OpenWrite(
	string path
)

Parameters

path
Type: System.String

The file to be opened for writing.

Return Value

Type: System.IO.FileStream
An unshared FileStream object on the specified path with Write access.

ExceptionCondition
UnauthorizedAccessException

The caller does not have the required permission.

-or-

path specified a read-only file or directory.

ArgumentException

path is a zero-length string, contains only white space, or contains one or more invalid characters as defined by InvalidPathChars.

ArgumentNullException

path is null.

PathTooLongException

The specified path, file name, or both exceed the system-defined maximum length. For example, on Windows-based platforms, paths must be less than 248 characters, and file names must be less than 260 characters.

DirectoryNotFoundException

The specified path is invalid, (for example, it is on an unmapped drive).

FileNotFoundException

The file specified in path was not found.

NotSupportedException

path is in an invalid format.

This method is equivalent to the FileStream(String, FileMode, FileAccess, FileShare) constructor overload.

If the file exists, it is opened for writing at the beginning. The existing file is not truncated.

The path parameter is permitted to specify relative or absolute path information. Relative path information is interpreted as relative to the current working directory. To obtain the current working directory, see GetCurrentDirectory.

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

The following example opens a file for reading and writing.

using System;
using System.IO;
using System.Text;

class Test 
{
    public static void Main() 
    {
        string path = @"c:\temp\MyTest.txt";

        // Create the file if it does not exist. 
        if (!File.Exists(path)) 
        {
            // Create the file. 
            using (FileStream fs = File.Create(path)) {}
        }

        // Open the stream and write to it. 
        using (FileStream fs = File.OpenWrite(path)) 
        {
            Byte[] info = 
                new UTF8Encoding(true).GetBytes("This is to test the OpenWrite method.");

            // Add some information to the file.
            fs.Write(info, 0, info.Length);
        }

        // Open the stream and read it back. 
        using (FileStream fs = File.OpenRead(path)) 
        {
            byte[] b = new byte[1024];
            UTF8Encoding temp = new UTF8Encoding(true);

            while (fs.Read(b,0,b.Length) > 0) 
            {
                Console.WriteLine(temp.GetString(b));
            }
        }
    }
}

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, 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, Zune

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.

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 3.5, 2.0, 1.0

XNA Framework

Supported in: 3.0, 2.0, 1.0

Community Additions

Show:
© 2015 Microsoft