OpenRead Method

File.OpenRead Method (String)


Opens an existing file for reading.

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

public static FileStream OpenRead(
	string path


Type: System.String

The file to be opened for reading.

Return Value

Type: System.IO.FileStream

A read-only FileStream on the specified path.

Exception Condition

path is a zero-length string, contains only white space, or contains one or more invalid characters as defined by InvalidPathChars.


path is null.


The specified path, file name, or both exceed the system-defined maximum length. For example, on Windows-based platforms, paths must be less than 248 characters, and file names must be less than 260 characters.


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


path specified a directory.


The caller does not have the required permission.


The file specified in path was not found.


path is in an invalid format.


An I/O error occurred while opening the file.

This method is equivalent to the FileStream(String, FileMode, FileAccess, FileShare) constructor overload with a FileMode value of Open, a FileAccess value of Read and a FileShare value of Read.

The path parameter is permitted to specify relative or absolute path information. Relative path information is interpreted as relative to the current working directory. To obtain the current working directory, see GetCurrentDirectory.

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

The following example opens a file for reading.

using System;
using System.IO;
using System.Text;

class Test 
    public static void Main() 
        string path = @"c:\temp\MyTest.txt";

        if (!File.Exists(path)) 
            // Create the file.
            using (FileStream fs = File.Create(path)) 
                Byte[] info = new UTF8Encoding(true).GetBytes("This is some text in the file.");

                // Add some information to the file.
                fs.Write(info, 0, info.Length);

        // Open the stream and read it back.
        using (FileStream fs = File.OpenRead(path)) 
            byte[] b = new byte[1024];
            UTF8Encoding temp = new UTF8Encoding(true);

            while (fs.Read(b,0,b.Length) > 0) 


for reading from the specified file. Associated enumeration: FileIOPermissionAccess.Read

Universal Windows Platform
Available since 10
.NET Framework
Available since 1.1
Available since 2.0
Windows Phone Silverlight
Available since 7.0
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