Hello,

We are having a problem with com interop. We have a Visual Foxpro dll (
FOXPRO 8 ) that returns an ADODB.Recordset

The fox dll is compiled as an Com+ dll. When we use that dll in ASP it works
fine. When we try to use it in a c# application ( Windows or ASP.NET ) we
keep getting exceptions.

The first idea was to try the same thing with a VB com+ dll, but the same
error occurs. It seems that the wrapper class generated by Visual studio .net
doesn't function correctly.

Below i will describe a few tests we did to find the source of the problem.
We have a Com dll with the following Fox Code

DEFINE CLASS testADODB as Session Olepublic
    PROCEDURE moGetRecordSet as ADODB.RecordSet
        loDB = CREATEOBJECT("test.testADODB_DB")
        RETURN loDB.moGetRecordSet
    ENDPROC
ENDDEFINE

DEFINE CLASS testADODB_DB as Session Olepublic
    PROCEDURE moGetRecordSet
        loRS = CREATEOBJECT("ADODB.RecordSet")
        RETURN loRS
    ENDPROC
ENDDEFINE

When i create a wrapper class in VS.NET 2003 ( By adding a reference to a
COM dll ) and call the Com DLL with the following c# code

test.testADODBClass testClass = new test.testADODBClass();
ADODB.Recordset recset = testClass.moGetRecordSet();
if( recset == null )
    return;
if( recset.State > 0 )
{
    lblResult.Text = "RecCount: " + recset.RecordCount;
}
else
{
    lblResult.Text = recset.GetType().ToString();
}

This code compiles just fine, but when I run this code i get an
ExecutionEngineException. When I look in the documentation of this exception
the remarks say: "Execution engine errors are fatal errors that should never
occur." so that doesn't help either.

The strange thing is that if I change the FOX dll defenition so that the
return type is a variant instead of a ADODB.Recordset and cast it to an
ADODB.Recordset in my C# code it works correctly.

I'm also pretty sure the Com dll is correct because it works fine in classic
asp and it is also possible to call the dll itself with the following C# code.

object comObj;
Type comType;
comType = Type.GetTypeFromProgID( "myComProgID" );
comObj = Activator.CreateInstance( comType );
object ret = comType.InvokeMember( "myComFunction"
	, BindingFlags.InvokeMethod | BindingFlags.Default
	, null
	, comObj
	, new object[]{ "param1","param2", "param3" } );
ADODB.Recordset recset = (ADODB.Recordset)ret;
MessageBox.Show( recset.RecordCount.ToString() );

So I think there is something wrong with the interop assembly generated by
VS.NET. How can i use the COM wrappers generated by VS.net without getting
this exception?