FileStream.CanWrite Property tells whether the current stream supports writing.
Imports System Imports System.IO Public Class Test Public Shared Sub Main() Dim path As String = "c:\temp\MyTest.txt" File.SetAttributes(path, File.GetAttributes(path) Or FileAttributes.ReadOnly) Dim fs As FileStream = New FileStream(path, FileMode.OpenOrCreate, FileAccess.Read) If fs.CanWrite Then Console.WriteLine("The stream connected to {0} is writable.", path) Else Console.WriteLine("The stream connected to {0} is not writable.", path) End If fs.Close() End Sub End Class