StreamWriter Constructor (Stream)

StreamWriter Constructor (Stream)


Initializes a new instance of the StreamWriter class for the specified stream by using UTF-8 encoding and the default buffer size.

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

public StreamWriter(
	Stream stream


Type: System.IO.Stream

The stream to write to.

Exception Condition

stream is not writable.


stream is null.

This constructor creates a StreamWriter with UTF-8 encoding without a Byte-Order Mark (BOM), so its GetPreamble method returns an empty byte array. The default UTF-8 encoding for this constructor throws an exception on invalid bytes. This behavior is different from the behavior provided by the encoding object in the Encoding.UTF8 property. To specify whether an exception is thrown on invalid bytes, use a constructor that accepts an encoding object as a parameter, such as StreamWriter. The BaseStream property is initialized using the stream parameter. The position of the stream is not reset.

The StreamWriter object calls Dispose() on the provided Stream object when StreamWriter.Dispose is called.


When you compile a set of characters with a particular cultural setting and retrieve those same characters with a different cultural setting, the characters might not be interpretable and could cause an exception to be thrown.

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

The following code example demonstrates this constructor.

using System;
using System.IO;

namespace ConsoleApplication
    class Program
        static void Main(string[] args)
            string fileName = "test.txt";
            string textToAdd = "Example text in file";
            FileStream fs = null;
                fs = new FileStream(fileName, FileMode.CreateNew);
                using (StreamWriter writer = new StreamWriter(fs))
                if (fs != null)

Universal Windows Platform
Available since 4.5
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
Return to top
© 2015 Microsoft