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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 Value

Type: System.Boolean
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);
            }
        }
    }
}

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.");
        }
    }
}

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Supported in: Windows Phone 8.1

Supported in: Windows Phone Silverlight 8.1

Supported in: Windows Phone Silverlight 8

Windows Phone 8.1, Windows Phone 8, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

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

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