Článek
11/18/2011

StreamReader Constructor (String, Encoding, Boolean, Int32)

Microsoft Silverlight will reach end of support after October 2021. Learn more.

When it is called by trusted applications, initializes a new instance of the StreamReader class for the specified file name, using the specified character encoding, byte order mark detection option, and buffer size.

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

Syntax

'Declaration
<SecuritySafeCriticalAttribute> _
Public Sub New ( _
    path As String, _
    encoding As Encoding, _
    detectEncodingFromByteOrderMarks As Boolean, _
    bufferSize As Integer _
)

[SecuritySafeCriticalAttribute]
public StreamReader(
    string path,
    Encoding encoding,
    bool detectEncodingFromByteOrderMarks,
    int bufferSize
)

Parameters

path
Type: System.String
The complete file path to be read.

encoding
Type: System.Text.Encoding
The character encoding to use.

detectEncodingFromByteOrderMarks
Type: System.Boolean
true to look for byte order marks at the beginning of the file; otherwise, false.

bufferSize
Type: System.Int32
The minimum buffer size, in number of 16-bit characters.

Exceptions

Exception	Condition
ArgumentException	path is an empty string ("").
ArgumentNullException	path or encoding is nulla null reference (Nothing in Visual Basic).
FileNotFoundException	The file cannot be found.
DirectoryNotFoundException	The specified path is invalid; for example, it might refer to an unmapped drive.
NotSupportedException	path includes an incorrect or invalid syntax for file name, directory name, or volume label.
ArgumentOutOfRangeException	buffersize is less than or equal to zero.

Remarks

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

This constructor enables 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.

Caution:
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.

Platform Notes

Silverlight for Windows Phone

This member has a SecurityCriticalAttribute attribute on Silverlight for Windows Phone, because the attribute was present in Silverlight 3. This attribute restricts this member to internal use. Application code that uses this member throws a MethodAccessException.

Version Information

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Xbox 360, Windows Phone OS 7.0

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

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