Association between ObjectItem and task

Hello,

I want to connect a task to an ObjectItem (in this case a cable). I tried it through EngineeringBase.Interop.dll and through an EB assistent. Both ways did not work. I get an exception, that the method is not allowed.
Below you find the code of the assistant. Am I doing something wrong or is this operation not supported (yet)? I can perform this operation through the GUI.
I am using EB Version 7.2.0 Build 1385.

public class MyPlugIn : PlugInWizard

    {

        /// <summary>

        ///     Runs the wizard.

        /// </summary>

        /// <param name="myApplication">Application object instance</param>

        public override void Run(Application myApplication)

        {

 

            var task = myApplication.ActiveProject.ExecutionTasksFolder.NewChild((ObjectKind)431, (ObjectType)2433, false);

            task.Attributes.FindById(AttributeId.Designation).Value = "Testaufgabe";

            task.Store();

 

            var cable = myApplication.ActiveProject.EquipmentFolder.NewChild(ObjectKind.Cable, ObjectType.CableUnspecified, false);

            cable.Attributes.FindById(AttributeId.Designation).Value = "Testkabel";

            cable.Store();

 

            try

            {

                task?.SourceAssociations.Add((AssociationRole)146, cable);

            }

            catch (Exception e)

            {

                MessageBox.Show(e.ToString());

                throw;

            }

        }

    }

Best regards
Matthias