File::OpenRead Method (String^)

.NET Framework (current version)

Opens an existing file for reading.

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

Syntax

public:
static FileStream^ OpenRead(
	String^ path
)

Parameters

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.

Exceptions

Exception	Condition
ArgumentException	path is a zero-length string, contains only white space, or contains one or more invalid characters as defined by InvalidPathChars.
ArgumentNullException	path is null.
PathTooLongException	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.
DirectoryNotFoundException	The specified path is invalid, (for example, it is on an unmapped drive).
UnauthorizedAccessException	path specified a directory. -or- The caller does not have the required permission.
FileNotFoundException	The file specified in path was not found.
NotSupportedException	path is in an invalid format.
IOException	An I/O error occurred while opening the file.

Remarks

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.

Examples

The following example opens a file for reading.

C++

using namespace System;
using namespace System::IO;
using namespace System::Text;

int main()
{
   String^ path = "c:\\temp\\MyTest.txt";

   if (  !File::Exists( path ) )
   {
      // Create the file.
      FileStream^ fs = File::Create( path );
      try
      {
         array<Byte>^info = (gcnew UTF8Encoding( true ))->GetBytes( "This is some text in the file." );

         // Add some information to the file.
         fs->Write( info, 0, info->Length );
      }
      finally
      {
         if ( fs )
            delete (IDisposable^)fs;
      }
   }

   // Open the stream and read it back.
   FileStream^ fs = File::OpenRead( path );
   try
   {
      array<Byte>^b = gcnew array<Byte>(1024);
      UTF8Encoding^ temp = gcnew UTF8Encoding( true );
      while ( fs->Read( b, 0, b->Length ) > 0 )
      {
         Console::WriteLine( temp->GetString( b ) );
      }
   }
   finally
   {
      if ( fs )
         delete (IDisposable^)fs;
   }
}

Security

FileIOPermission

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

Version Information

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