Can we use this FileSystem.FileOpen

In C# we write this code system generate error
The type or namespace name 'FileSystem' could not be found (are you missing a using directive or an assembly reference?)


which library import

FileSystem.FileOpen(2, "Connection.dll", OpenMode.Binary, OpenAccess.Default, OpenShare.Default, -1);

Are you sure you are not refering to System.IO.FileInfo?
It got 3 overloaded Open methods as follows:
Open(FileMode);
Open(FileMode, FileAccess);
Open(FileMode, FileAccess, FileShare);

FileSystem is a module in the Microsoft.VisualBasic namespace. You can add a reference to the Microsoft.VisualBasic assembly to a C# project and then use the member modules as though they were classes with static members, but I suggest that you just use the System.IO namespace and its members instead, as I suggest that you do in VB.NET as well.