StreamReader Constructor (String, Encoding, Boolean, Int32)


Initializes a new instance of the StreamReader class for the specified file name, with the specified character encoding, byte order mark detection option, and buffer size.

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

new : 
        path:string *
        encoding:Encoding *
        detectEncodingFromByteOrderMarks:bool *
        bufferSize:int -> StreamReader


Type: System.String

The complete file path to be read.

Type: System.Text.Encoding

The character encoding to use.

Type: System.Boolean

Indicates whether to look for byte order marks at the beginning of the file.

Type: System.Int32

The minimum buffer size, in number of 16-bit characters.

Exception Condition

path is an empty string ("").


path or encoding is null.


The file cannot be found.


The specified path is invalid, such as being on an unmapped drive.


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


buffersize is less than or equal to zero.

This constructor initializes the encoding as specified by the encoding parameter.

This constructor allows you to change the encoding the first time you read from the StreamReader object. The detectEncodingFromByteOrderMarks parameter detects the encoding by looking at the first three bytes of the stream. It automatically recognizes UTF-8, little-endian Unicode, and big-endian Unicode text if the file starts with the appropriate byte order marks. Otherwise, the user-provided encoding is used. See the Encoding.GetPreamble method for more information.

The buffer size, in number of 16-bit characters, is set by the bufferSize parameter. If bufferSize is less than the minimum allowable size (128 characters), the minimum allowable size is used.

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 StreamReader constructor.

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

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