I came across the same problem with C-style arrays only last week. I solved it the same way.
I have been getting some very odd behavior though - ExecutionEngineExceptions and other random exceptions (even exceptions which claim I am unable to write to the EventLog, which is patently false). So, reluctantly, I've decided to write an unmanaged proxy which converts a C-style array method into a SafeArray. Regards, Richard > -----Original Message----- > From: Moderated discussion of advanced .NET topics. > [mailto:[EMAIL PROTECTED]]On Behalf Of Andrew Hopper > Sent: 14 October 2002 15:37 > To: [EMAIL PROTECTED] > Subject: Re: [ADVANCED-DOTNET] FW: Interop: Handling OUT parameter of > array, gets error "Can not use SizeParamIndex for byref array > parameters."?? > > > Hello, Thomas- > > From what I understand, using the SizeParamIndex to marshal arrays only > works for marshaling data from managed code into COM and will not work > for out parameters. Due to this, I'm afraid you won't be able to use the > default marshaling provided by the framework. However, you should still > be able to accomplish this task - it will simply require a little more > work on your part. > > I would change the method declaration to be: > ... > // Eliminate PreserveSig unless you need to interpret the HRESULT > /// <summary> > /// The Next method retrieves a specified number of pins in the > enumeration sequence > /// </summary> > /// <param name="cPins">Number of pins to retrieve</param> > /// <param name="ppPins">Array of size cPins that is filled with IPin > pointers</param> > /// <param name="pcFetched">Pointer to a variable that receives the > number of pins retrieved</param>void Next( > // Pass the count we expect > int cPins, > // pass a pointer to a pointer that points to allocated memory > ref IntPtr ppPins, > // pass a pointer to an int that will be filled with the count > out int pcFetched > ); > ... > > You would then have to wrap the method call in some helper code: > // I'm assuming you already have obtained a pointer to > // the IEnumPins interface and stored it in pEnum... > IEnumPins pEnum; > int numPins, > cFetched, > sizeOfIntPtr; > IntPtr pPinArray = IntPtr.Zero, > pPin; > IPin[] arrayOfPins; > > try > { > // This is kind of anal - you could easily just use 4 instead of > calculating > // the size... > sizeOfIntPtr = Marshal.SizeOf(typeof(IntPtr)); > > numPins = 42; //Put some real number here... > // Allocate space to hold the array > pPinArray = Marshal.AllocCoTaskMem[sizeOfIntPtr * numPins]; > // Fill the array > pEnum.Next(numPins, ref pPinArray, out cFetched); > // Allocate space to hold the array of interfaces > arrayOfPins = new IPin[cFetched]; > // Load the array elements > for(int counter = 0; counter < cFetched; counter++) > { > // nibble off an IntPtr at a time, > // incrementing the offset as we go > pPin = Marshal.ReadIntPtr(pPinArray, counter * sizeOfIntPtr); > // convert the IntPtr to a managed pointer to an IPin > arrayOfPins[counter] = (IPin)Marshal.GetObjectForIUnknown(pPin); > } > } > finally > { > if(pPinArray != IntPtr.Zero) Marshal.FreeCoTaskMem(pPinArray); > } > > // Do something with the array > ... > > Hope this works (and helps)! > -Andy Hopper > > > -----Original Message----- > From: Moderated discussion of advanced .NET topics. > [mailto:[EMAIL PROTECTED]] On Behalf Of Thomas > Tomiczek > Sent: Monday, October 14, 2002 6:49 AM > To: [EMAIL PROTECTED] > Subject: [ADVANCED-DOTNET] FW: Interop: Handling OUT parameter of array, > gets error "Can not use SizeParamIndex for byref array parameters."?? > > > > Hello, simple question (so to say). > > > > I ham trying to manage interoo for interface arrays. > > > > This interface definition is not working. It is for a DirectShow > > Interface: > > > > [ComVisible(true), ComImport, > > Guid("56a86892-0ad4-11ce-b03a-0020af0ba770"), > > InterfaceType( ComInterfaceType.InterfaceIsIUnknown )] > > public interface IEnumPins { > > [PreserveSig] > > int Next( > > [In] int cPins, > > [Out, MarshalAs(UnmanagedType.LPArray, > > SizeParamIndex=2)] out IPin[] ppPins, > > [Out] out int pcFetched ); > > > > [PreserveSig] > > int Skip( [In] int cPins ); > > void Reset(); > > void Clone( [Out] out IEnumPins ppEnum ); > > } > > > > When trying to use the next function, I get this error: > > > > An unhandled exception of type > > 'System.Runtime.InteropServices.MarshalDirectiveException' occurred in > > > thonaconsulting.directshow.dll > > Additional information: Can not use SizeParamIndex for byref > > array parameters. > > > > That is sad, because I stop having clues on how to get this out. > > Basically I try to get the next x pins. The 2nd parameter (index 1) > > returns an array to the pints taken, and the third parameter returns > > the number of pins put into the arrray. > > > > The error appears under .NET framework 1.1 - no way to check 1.0 > > easly. > > > The stack trace shows that the error apears within the marshalling: > > at ThonaConsulting.DirectShow.IEnumPins.Next(Int32 cPins, IPin[]& > ppPins, Int32& pcFetched) > at > ThonaConsulting.DirectShow.Utilities.FilterUtility.GetPin(IBaseFilter > Filter, PinDirection Direction) in > c:\work\thonaconsulting\directshow\thonaconsulting.directshow\utilities\ > filterutility.cs:line 29 > > > Any clues? > > > > Thomas Tomiczek > > THONA Consulting Ltd. > > (Microsoft MVP C#/.NET) > > You can read messages from the Advanced DOTNET archive, unsubscribe from > Advanced DOTNET, or subscribe to other DevelopMentor lists at > http://discuss.develop.com. > > You can read messages from the Advanced DOTNET archive, > unsubscribe from Advanced DOTNET, or > subscribe to other DevelopMentor lists at http://discuss.develop.com. You can read messages from the Advanced DOTNET archive, unsubscribe from Advanced DOTNET, or subscribe to other DevelopMentor lists at http://discuss.develop.com.
