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createstreamonhglobal (ole32)
 
.
Summary

C# Signature:

[DllImport("ole32.dll")]
static extern int CreateStreamOnHGlobal(IntPtr hGlobal, bool fDeleteOnRelease,
   out UCOMIStream ppstm);

VB.NET Signature:

    Declare Function CreateStreamOnHGlobal Lib "ole32" (ByVal hGlobal As IntPtr, ByVal fDeleteOnRelease As Boolean, ByRef ppstm As UCOMIStream) As Long

User-Defined Types:

None.

Notes:

None.

Tips & Tricks:

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Sample Code:

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Alternative Managed API:

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Documentation
From
K. Lazar - C# - kentscode@yahoo.com

Use this signature

       [System.Runtime.InteropServices.DllImport("OLE32.DLL", EntryPoint = "CreateStreamOnHGlobal")] // Create a COM stream from a pointer in unmanaged memory
    extern public static int CreateStreamOnHGlobal(IntPtr ptr, bool delete, out System.Runtime.InteropServices.ComTypes.IStream pOutStm);
    [System.Runtime.InteropServices.DllImport("OLE32.DLL", EntryPoint = "GetHGlobalFromStream")]
    public extern static void GetHGlobalFromStream(IStream stm, ref IntPtr hGlobal);

    public bool PersistLoadComObject(object objComCtrl, string strGUID, byte[] buffer)
    {
        IStream comStream;
        IntPtr  pIPStream = IntPtr.Zero;
        IntPtr  hGlobalMemHandle = (IntPtr)null;
        IntPtr  pIUnk = IntPtr.Zero;
        bool    bRetc=true;
        bool    fClearDirty;
        Int32   iUseCount;
        int     iResult;
        int     S_OK = 0;
        int     E_FAIL = unchecked((int)0x80004005);
        int     E_NOINTERFACE = unchecked((int)0x80004002);
        Guid    IID_IPersistStreamInit = new Guid("7FD52380-4E07-101B-AE2D-08002B2EC713");

        if (Marshal.IsComObject((object)objComCtrl))
        {
        pIUnk = Marshal.GetIUnknownForObject((object)objComCtrl); // returns a pointer to a pointer of the object’s IUnknown Interface
        //Int32 usecount1 = Marshal.AddRef(pIUnk);  // increments the use count
        if (pIUnk == IntPtr.Zero)
        {
            ErrorMsg = "GetIUnknownForObject was zero.";
        }
        else
        {   // get a pointer to IPersistStreamInit interface
            iResult = Marshal.QueryInterface(pIUnk, ref IID_IPersistStreamInit, out pIPStream); // returns a pointer to a pointer for a specified Interface
            if (iResult == E_NOINTERFACE)
            {
            ErrorMsg = "No such interface supported";
            bRetc = false;
            }
            else if (iResult == E_FAIL)
            {
            ErrorMsg = "PersistStreamInit QueryInit failed.";
            bRetc = false;
            }
            else if (iResult == S_OK)
            {
            IPersistStreamInit pPersistStream = (IPersistStreamInit)Marshal.GetObjectForIUnknown(pIPStream);
            int SizeOfIstream = ByteSizeOfIPStreamInit(pPersistStream) * 2;  // two bytes per value -- See my OleSaveToStream (ole32)              
            if (CheckGUIDS(pPersistStream, strGUID))
            {
                IntPtr nativePtr = Marshal.AllocHGlobal(SizeOfIstream); //buffer.Length); // allocate space on the native heap
                Marshal.Copy(buffer, 0, nativePtr, SizeOfIstream);      // copy byte array to native heap
                if (CreateStreamOnHGlobal(nativePtr, true, out comStream) == S_OK) // Create IStream from allocated memory that has buffer data
                {
                 pPersistStream.Load(comStream);
                 fClearDirty = true;
                 pPersistStream.Save(comStream, fClearDirty);
                }
            }
            Marshal.Release(pIPStream);
            }
            iUseCount = Marshal.Release(pIUnk); // decrements the use count
        }
        }
        return (bRetc);
    }

     public bool CheckGUIDS(IPersistStreamInit pPersistStream, string strCtrlGUID)
     {
          bool retc = true;
          Guid ptrClsId = new Guid();
          pPersistStream.GetClassID(ref ptrClsId);
          string strStreamGUID = ptrClsId.ToString().ToUpper();

          if (strStreamGUID != strCtrlGUID.ToUpper())
          {
          _strErrorMsg = strStreamGUID + " " + strCtrlGUID + " mismatch";
          retc = false;
          }
          return (retc);
     }

     public string ErrorMsg
     {
          get {return _strErrorMsg;}
          set {_strErrorMsg = value;}
     }

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