C# Definition:

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

VB Definition:

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

User-Defined Field Types:

None.

Notes:

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