StreamWriter Constructor (String)

StreamWriter Constructor (String)


Initializes a new instance of the StreamWriter class for the specified file by using the default encoding and buffer size.

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

public StreamWriter(
	string path


Type: System.String

The complete file path to write to. path can be a file name.

Exception Condition

Access is denied.


path is an empty string ("").


path contains the name of a system device (com1, com2, and so on).


path is null.


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


The specified path, file name, or both exceed the system-defined maximum length. For example, on Windows-based platforms, paths must not exceed 248 characters, and file names must not exceed 260 characters.


path includes an incorrect or invalid syntax for file name, directory name, or volume label syntax.


The caller does not have the required permission.

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 a BOM and determine whether an exception is thrown on invalid bytes, use a constructor that accepts an encoding object as a parameter, such as StreamWriter(String, Boolean, Encoding).

The path parameter can be a file name, including a file on a Universal Naming Convention (UNC) share. If the file exists, it is overwritten; otherwise, a new file is created.

The path parameter is not required to be a file stored on disk; it can be any part of a system that supports access using streams.


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;
using System.Text;

namespace ConsoleApplication
    class Program
        static void Main(string[] args)
            string fileName = "test.txt";
            string textToAdd = "Example text in file";

            using (StreamWriter writer = new StreamWriter(fileName))

for reading and writing files. Associated enumeration: FileIOPermissionAccess.Read, FileIOPermissionAccess.Write

.NET Framework
Available since 1.1
Available since 2.0
Windows Phone Silverlight
Available since 7.0
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