File.OpenRead(String) Method
Definition
Opens an existing file for reading.
public:
static System::IO::FileStream ^ OpenRead(System::String ^ path);
public static System.IO.FileStream OpenRead (string path);
static member OpenRead : string -> System.IO.FileStream
Public Shared Function OpenRead (path As String) As FileStream
Parameters
- path
- String
The file to be opened for reading.
Returns
A read-only FileStream on the specified path.
Exceptions
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.
The specified path is invalid, (for example, it is on an unmapped drive).
path
specified a directory.
-or-
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.
Examples
The following example opens a file for reading.
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;
}
}
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)
{
Console.WriteLine(temp.GetString(b));
}
}
}
}
Imports System.IO
Imports System.Text
Public Class Test
Public Shared Sub Main()
Dim path As String = "c:\temp\MyTest.txt"
If Not File.Exists(path) Then
' Create the file.
Using fs As FileStream = File.Create(path)
Dim info As Byte() = New UTF8Encoding(True).GetBytes("This is some text in the file.")
' Add some information to the file.
fs.Write(info, 0, info.Length)
End Using
End If
' Open the stream and read it back.
Using fs As FileStream = File.OpenRead(path)
Dim b(1023) As Byte
Dim temp As UTF8Encoding = New UTF8Encoding(True)
Do While fs.Read(b, 0, b.Length) > 0
Console.WriteLine(temp.GetString(b))
Loop
End Using
End Sub
End Class
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.