C# Definition:

       /// <summary>
    /// contains information about the current state of both physical and virtual memory, including extended memory
    /// </summary>
    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto)]
    public class MEMORYSTATUSEX
    {
        /// <summary>
        /// Size of the structure, in bytes. You must set this member before calling GlobalMemoryStatusEx.
        /// </summary>
        public uint dwLength;

        /// <summary>
        /// Number between 0 and 100 that specifies the approximate percentage of physical memory that is in use (0 indicates no memory use and 100 indicates full memory use).
        /// </summary>
        public uint dwMemoryLoad;

        /// <summary>
        /// Total size of physical memory, in bytes.
        /// </summary>
        public ulong ullTotalPhys;

        /// <summary>
        /// Size of physical memory available, in bytes.
        /// </summary>
        public ulong ullAvailPhys;

        /// <summary>
        /// Size of the committed memory limit, in bytes. This is physical memory plus the size of the page file, minus a small overhead.
        /// </summary>
        public ulong ullTotalPageFile;

        /// <summary>
        /// Size of available memory to commit, in bytes. The limit is ullTotalPageFile.
        /// </summary>
        public ulong ullAvailPageFile;

        /// <summary>
        /// Total size of the user mode portion of the virtual address space of the calling process, in bytes.
        /// </summary>
        public ulong ullTotalVirtual;

        /// <summary>
        /// Size of unreserved and uncommitted memory in the user mode portion of the virtual address space of the calling process, in bytes.
        /// </summary>
        public ulong ullAvailVirtual;

        /// <summary>
        /// Size of unreserved and uncommitted memory in the extended portion of the virtual address space of the calling process, in bytes.
        /// </summary>
        public ulong ullAvailExtendedVirtual;

        /// <summary>
        /// Initializes a new instance of the <see cref="T:MEMORYSTATUSEX"/> class.
        /// </summary>
        public MEMORYSTATUSEX()
        {
        this.dwLength = (uint)Marshal.SizeOf(typeof(NativeMethods.MEMORYSTATUSEX));
        }
       }

VB Definition:

<StructLayout(LayoutKind.Sequential, CharSet:=CharSet.Auto)> _

Public Class MEMORYSTATUSEX

     ''' <summary>
     ''' Initializes a new instance of the <see cref="T:MEMORYSTATUSEX" /> class.
     ''' </summary>
     Public Sub New()
          Me.dwLength = CType(Marshal.SizeOf(GetType(MEMORYSTATUSEX)), UInt32)
     End Sub


      ' Fields
      ''' <summary>
      ''' Size of the structure, in bytes. You must set this member before calling GlobalMemoryStatusEx.
      ''' </summary>
      Public dwLength As UInt32
      ''' <summary>
      ''' Number between 0 and 100 that specifies the approximate percentage of physical memory that is in use (0 indicates no memory use and 100 indicates full memory use).
      ''' </summary>
      Public dwMemoryLoad As UInt32
      ''' <summary>
      ''' Size of unreserved and uncommitted memory in the extended portion of the virtual address space of the calling process, in bytes.
      ''' </summary>
      Public ullAvailExtendedVirtual As UInt64
      ''' <summary>
      ''' Size of available memory to commit, in bytes. The limit is ullTotalPageFile.
      ''' </summary>
      Public ullAvailPageFile As UInt64
      ''' <summary>
      ''' Size of physical memory available, in bytes.
      ''' </summary>
      Public ullAvailPhys As UInt64
      ''' <summary>
      ''' Size of unreserved and uncommitted memory in the user mode portion of the virtual address space of the calling process, in bytes.
      ''' </summary>
      Public ullAvailVirtual As UInt64
      ''' <summary>
      ''' Size of the committed memory limit, in bytes. This is physical memory plus the size of the page file, minus a small overhead.
      ''' </summary>
      Public ullTotalPageFile As UInt64
      ''' <summary>
      ''' Total size of physical memory, in bytes.
      ''' </summary>
      Public ullTotalPhys As UInt64
      ''' <summary>
      ''' Total size of the user mode portion of the virtual address space of the calling process, in bytes.
      ''' </summary>
      Public ullTotalVirtual As UInt64

End Class

User-Defined Field Types:

None.

Notes: