C# Definition:

private struct MEMORYSTATUSEX
{
    public int Length;
    public int MemoryLoad;
    public ulong TotalPhysical;
    public ulong AvailablePhysical;
    public ulong TotalPageFile;
    public ulong AvailablePageFile;
    public ulong TotalVirtual;
    public ulong AvailableVirtual;
    public ulong AvailableExtendedVirtual;
}

VB Definition:

Structure MEMORYSTATUSEX
   Public Length As Integer
   Public MemoryLoad As Integer
   Public TotalPhysical As ULong
   Public AvailablePhysical As ULong
   Public TotalPageFile As ULong
   Public AvailablePageFile As ULong
   Public TotalVirtual As ULong
   Public AvailableVirtual As ULong
   Public AvailableExtendedVirtual As ULong
End Structure

User-Defined Field Types:

None.

Notes:

Length must be filled in before calling the GlobalMemoryStatusEx method, using Marshal.Sizeof() method