static extern uint GetFullPathName(string lpFileName, uint nBufferLength,

Shared Function GetFullPathName(ByVal lpFileName As String, ByVal nBufferLength As Int32, <Out()> ByVal lpBuffer As System.Text.StringBuilder, <Out()> ByVal lpFilePart As System.Text.StringBuilder) As Int32

uint u = GetFullPathName(sRel, (uint)bufsz, sbFull, out sbFile);  // 1st call: Get necessary bufsz

   u = GetFullPathName(sRel, (uint)bufsz, sbFull, out sbFile);    // Try again, this should succeed