StreamWriter Constructor (String, Boolean)


Initializes a new instance of the StreamWriter class for the specified file by using the default encoding and buffer size. If the file exists, it can be either overwritten or appended to. If the file does not exist, this constructor creates a new file.

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

new : 
        path:string *
        append:bool -> StreamWriter


Type: System.String

The complete file path to write to.

Type: System.Boolean

true to append data to the file; false to overwrite the file. If the specified file does not exist, this parameter has no effect, and the constructor creates a new file.

Exception Condition

Access is denied.


path is empty.


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).


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


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.


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.

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.

No code example is currently available or this language may not be supported.

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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