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Dynamic Class Loading & System.__COMObject

Hi y'all, here's a tricky one:

I've written a wrapper around a Com Interop-generated assembly in C#. It's
called SDEHandler & implements a previously defined interface, so that I can
use it as a provider, and load instances of it dynamically. In other words,
I use it as a "plugin implementation" of a well-known API (a Provider?).

Inside it I create a DataSet, which gets filled with at least a column
containing values of type SDEPoint, a little struct I've written inside the
SDEHandler assembly, that describes a Point with X,Y doubles as fields.

My problem is that after the caller has executed a method resulting in that
DataSet on a dynamically loaded instance of the SDEHandler, the DataSet
seems to contain instead of SDEPoint instances, objects of type
System.__ComObject.

Casting that into an SDEPoint fails miserably, kust like my other efforts by
using System.Activator, ObjectHandle & ObjRef.

Can anyone point out anything that might be causing me all that frustration
???

Some code snippets:

1) The code that creates the SDEHandler instance in the first place:

public IActionHandler GetHandler(DataSource.DataSource source){
ActionHandlerDescriptor descriptor =
(ActionHandlerDescriptor)handlerDescriptors[source.Type];
if(descriptor==null)
throw new ConfigurationException("Unknown Data Source Type:
"+source.Type);
string strClassName = descriptor.HandlerClass;
string strAssemblyName = descriptor.HandlerAssembly;
//Instantiate an ActionHandler for the given data source name ...
try{
ObjectHandle oPntr = Activator.CreateInstance(strAssemblyName,
strClassName);
return (IActionHandler)oPntr.Unwrap();
}catch(Exception e){
throw new InitialisationException(e);
}
}
2) the code inside the action handler, that fills the DataSet:
... blah-blah ...
for(int i=0; i<rsCount; i++){
try{
int index = 0;
object[] values = new object[rs.TableDesc.FieldCount+1];
// try to get the SHAPE from the recordset ...
try{
Field shape = rs.Fields.Item("SHAPE");
object val = shape.Value;
Console.Out.WriteLine("SHAPE is a point? {0}", (val is
MapObjects2.Point));
values[(values.Length-1)] =
Utilities.ToSDEPoint((MapObjects2.Point)val);
}catch(Exception e){
Console.Out.WriteLine("Failed to get the SHAPE field: {0}", e.Message);
}
foreach(DataColumn col in tbl.Columns){
string strColName = col.ColumnName;
Field fld = rs.Fields.Item(strColName);
values[index] = (fld!=null)?fld.Value:null;
index++;
}
tbl.Rows.Add(values);
rs.MoveNext();
}catch(Exception e){
Console.WriteLine("Exception while parsing rs: {0}", e.Message);
break;
}
}
3) And the code that parses the DataSet & prints out the cols/values ...
public static void PrintDataTable(DataTable dt){
Console.Out.WriteLine("Printing Table:"+dt.TableName);
DataColumnCollection cols = dt.Columns;
foreach(DataRow row in dt.Rows){
for(int i=0; i<cols.Count; i++){
object val = row[i];
Console.Out.WriteLine("Val is a {0}", val.GetType().ToString());
Console.Out.WriteLine(cols[i].ColumnName+" = "+row[i]);
}
}
}

... apparently, all my SDEPoint instances have become System.__ComObject
instances somehow, that will refuse any type of casting, or simple way of
interrogation about properties

Cheers.
Angel
O:]
Jul 21 '05 #1
0 1724

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