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FileStream.CanWrite Property

Gets a value indicating whether the current stream supports writing.

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

public override bool CanWrite { get; }
/** @property */
public boolean get_CanWrite ()

public override function get CanWrite () : boolean

Property Value

true if the stream supports writing; false if the stream is closed or was opened with read-only access.

If a class derived from Stream does not support writing, a call to SetLength, Write, BeginWrite, or WriteByte throws a NotSupportedException.

If the stream is closed, this property returns false.

The following example uses the CanWrite property to check whether a stream supports writing.

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

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

        // Ensure that the file is readonly.
        File.SetAttributes(path, File.GetAttributes(path) | FileAttributes.ReadOnly);

        //Create the file.
        using (FileStream fs = new FileStream (path, FileMode.OpenOrCreate, FileAccess.Read)) 
        {
            if (fs.CanWrite) 
            {
                Console.WriteLine("The stream for file {0} is writable.", path);
            } 
            else 
            {
                Console.WriteLine("The stream for file {0} is not writable.", path);
            }
        }
    }
}

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

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

        // Ensure that the file is readonly.
        File.SetAttributes(path, File.GetAttributes(path) | FileAttributes.
            ReadOnly);

        //Create the file.
        FileStream fs = new FileStream(path, FileMode.OpenOrCreate, 
            FileAccess.Read);
        try {
            if (fs.get_CanWrite()) {
                Console.WriteLine("The stream for file {0} is writable.",
                    path);
            }
            else {
                Console.WriteLine("The stream for file {0} is not writable.",
                    path);
            }
        }
        finally {
            fs.Dispose();
        }
    } //main
} //Test

The following is an example using the CanWrite property. The output of this code is "MyFile.txt is writable." To get the output message "MyFile.txt can be both written to and read from.", change the FileAccess parameter to ReadWrite in the FileStream constructor.

using System;
using System.IO;
 
class TestRW 
{
    public static void Main(String[] args)
    {
        FileStream fs = new FileStream("MyFile.txt", FileMode.OpenOrCreate, FileAccess.Write);
        if (fs.CanRead && fs.CanWrite)
        {
            Console.WriteLine("MyFile.txt can be both written to and read from.");
        }
        else if (fs.CanWrite)
        {
            Console.WriteLine("MyFile.txt is writable.");
        }
    }
}

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

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

.NET Framework

Supported in: 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0, 1.0

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