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:
Please add some!
Alternative Managed API:
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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;}
}
