I am developing an application in C# using Microsoft visual studio .NET 2003.
Basically, I imported a com dll in my application by adding reference to the
COM dll.  The com event in the original dll has the following signature:

HSESULT AddModifyGroupIndication(
[in] unsigned long groupListSize,
[in, size_is(groupListSize)] groupListStruct* groupList)

where groupListSize is number of items (structures) the groupList pointer is
pointing to and
groupList is a pointer to first item (structure of type groupListStruct) in
the memory.

when I imported the dll, the .NET interop marshaller converted the above
event as follows:

.method public hidebysig newslot abstract virtual
           instance void  AddModifyGroupIndication(
[in] valuetype unsigned int32 groupListSize,
[in] valuetype TCSAPILib.groupListStruct& groupList) runtime managed
internalcall

As shown above the pointer (groupList) to first structure in the memory got
converted to a reference (ref) to the structure.

I am doing the following in AddModifyGroupIndication event handler in C# to
get all the items (structures) but it does not work:

------------------
private void RadioSubscriberManagerClass_AddModifyGroupIndication(
uint groupListSize,
ref TCSAPILib.groupListStruct groupList)
{

IntPtr fp;
IntPtr np;
TCSAPILib.groupListStruct  obj ;           
           
unsafe
{                               
int size = System.Runtime.InteropServices.Marshal.SizeOf(typeof
(TCSAPILib.groupListStruct  ));

fp = new IntPtr(size*(groupListSize));                               
try
{                   
  fp = System.Runtime.InteropServices.Marshal.AllocCoTaskMem(size* (int)  
groupListSize);                       
 
System.Runtime.InteropServices.Marshal.StructureToPtr groupList,fp,true);
                                                                               
for ( int i = 0; i < groupListSize; i ++ )
{                       
   np = new IntPtr((int)fp + (i * size));                                  
         
 
obj  = (TCSAPILib.groupListStruct )  
System.Runtime.InteropServices.Marshal.PtrToStructure( np,
typeof(TCSAPILib.groupListStruct ));

OnDebugEvt("---"+obj.groupAddress.ssi.ToString()); //debug
}
}
catch (Exception e1)
{
 OnDebugEvt("---Exception: "+e1.ToString());
}
finally
{
   System.Runtime.InteropServices.Marshal.FreeCoTaskMem(fp);   
}

}       

-------------------------------

The problem----
1.  The problem is StructureToPtr method seems to be coping only first
structure from the memory.
2.  As we cannot not get memory address of a managed type (groupList), how
would I get the remaining items (structures) in the memory in my event
handler.