Add Linked Parameter

[C-Hoppen]

Hello,

I need to add a parameter to an existing DerivedParameterTable:

Inventor.ObjectCollection oParamsLinken;
oParamsLinken = oApp.TransientObjects.CreateObjectCollection();

Inventor.Parameter p1 = oParamsSteuerbauteil["beh"];
oParamsLinken.Add(p1);

// oAssmDefSteuerbaugruppe.Parameters.DerivedParameterTables.Count is 0

Inventor.DerivedParameterTable oDerivedParamTable;
oDerivedParamTable = oAssmDefSteuerbaugruppe.Parameters.DerivedParameterTables.Add2(
   oPartDocSteuerbauteil.FullFileName,
   oParamsLinken);

// oAssmDefSteuerbaugruppe.Parameters.DerivedParameterTables.Count is 1

// *** Test                     

// link a second parameter
//
Inventor.Parameter p2 = oParamsSteuerbauteil["fpu_z"];

// works:
//
oParamsLinken.Add(p2);
oDerivedParamTable.LinkedParameters = oParamsLinken;

// fails:
//
//Inventor.DerivedParameterTable oDerivedParamTable2;
//oDerivedParamTable2 = oAssmDefSteuerbaugruppe.Parameters.DerivedParameterTables[1];

//Inventor.ObjectCollection oParamsLinken2;
//oParamsLinken2 = oDerivedParamTable2.LinkedParameters;

//oParamsLinken2.Add(p2);

//oDerivedParamTable2.LinkedParameters = oParamsLinken2; // <--- throws an "unknown exeption"

// *** Test

The first part works fine (as shown in api sample "Selectively link paramaters").

The second part fails. How can I add a parameter later? Assume the file was saved, closed an reopened.

Thanks

Christoph