File.Open Method (String, FileMode, FileAccess)
Opens a FileStream on the specified path, with the specified mode and access.
Assembly: mscorlib (in mscorlib.dll)
'Declaration Public Shared Function Open ( _ path As String, _ mode As FileMode, _ access As FileAccess _ ) As FileStream 'Usage Dim path As String Dim mode As FileMode Dim access As FileAccess Dim returnValue As FileStream returnValue = File.Open(path, mode, _ access)
- Type: System.String
The file to open.
- Type: System.IO.FileMode
A FileMode value that specifies whether a file is created if one does not exist, and determines whether the contents of existing files are retained or overwritten.
path is a zero-length string, contains only white space, or contains one or more invalid characters as defined by InvalidPathChars.
access specified Read and mode specified Create, CreateNew, Truncate, or Append.
path is Nothing.
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).
An I/O error occurred while opening the file.
path specified a file that is read-only and access is not Read.
path specified a directory.
The caller does not have the required permission.
mode is Create and the specified file is a hidden file.
mode or access specified an invalid value.
The file specified in path was not found.
path is in an invalid format.
The following example opens a file with read-only access.
Imports System Imports System.IO Imports System.Text Public Class Test Public Shared Sub Main() ' This sample assumes that you have a folder named "c:\temp" on your computer. Dim filePath As String = "c:\temp\MyTest.txt" Dim fs As FileStream ' Delete the file if it exists. If File.Exists(filePath) = True Then File.Delete(filePath) End If ' Create the file. fs = File.Create(filePath) 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) fs.Close() ' Open the stream and read it back. fs = File.Open(filePath, FileMode.Open, FileAccess.Read) Dim b(1024) As Byte Dim temp As UTF8Encoding = New UTF8Encoding(True) ' Display the information on the console. Do While fs.Read(b, 0, b.Length) > 0 Console.WriteLine(temp.GetString(b)) Loop Try ' Try to write to the file fs.Write(b, 0, b.Length) Catch e As Exception Console.WriteLine("Writing was disallowed, as expected: " & e.ToString()) End Try fs.Close() End Sub End Class
Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune
The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.