Help in converting vb.net function to C#.net

[nurcky]

I need help converting vb.net code to c#. here it is.

    'Get the ID File Type from file path name
    Public Function GetFileType(ByVal fileName As String) As EFile
        Dim i As Integer
        For i = 0 To SFile
            If InStr(1, fileName, VTFile(i).fileExt) = Len(fileName) - Len(VTFile(i).fileExt) + 1 Then
                GetFileType = VTFile(i).fileID
                Exit Function
            End If
        Next
        GetFileType = EFile.NOTDEF
    End Function

**Edited:**

This is what i got so far in C#

        //Get the ID File Type from file path name
        public EFile GetFileType(string fileName)
        {
            EFile functionReturnValue = default(EFile);
            int i = 0;
            for (i = 0; i <= SFile; i++)
            {
                if (Strings.InStr(1, fileName, VTFile[i].fileExt) == Strings.Len(fileName) - Strings.Len(VTFile[i].fileExt) + 1)
                {
                    functionReturnValue = VTFile[i].fileID;
                    return functionReturnValue;
                }
            }
            functionReturnValue = EFile.NOTDEF;
            return functionReturnValue;
        }

i get errors at this line:

    if (Strings.InStr(1, fileName, VTFile[i].fileExt) == Strings.Len(fileName) - Strings.Len(VTFile[i].fileExt) + 1)

its complaining of "Strings.IpStr( )" and "Strings.Len()" .
Error code:The name 'Strings' does not exist in the current context.

thanks in advance