Setting OwnerId of a custom activity
I have created a custom CRM activity that I'm using in a workflow. 
I'm  using this activity as an InArgument to a custom workflow activity. 
In the Execute() method I'm trying to set the OwnerId of the custom CRM activity instance to a system user and calling UpdateObject(entity) on the context object that I have generated using CrmSvcUtil. 


    [Input("Some name")]
    [ReferenceEntity("mycustomactivity")]
    [Required]
    public InArgument<EntityReference> MyCustomActivity{get;set;}


    void Execute(CodeActivityContext context)
    {
    IOrganizationService svc = context.GetExtension<IOrganizationService>();
    var customActivityReference = MyCustomActivity.GetValue(MyCustomActivity);

    //MyServiceContext is an OrganizationServiceContext generated using CrmSvcUtil
    MyServiceContext servicecontext = new MyServiceContext(svc); 
    
    //GetCutomActivityInstance uses the Id to get an instance of the custom activity) 
    MyCustomCRMActivity activityInstance = GetCutomActivityInstance (servicecontext,customActivityReference.Id);

    activityInstance.OwnerId = new EntityReference("systemuser",<SomeGUID>);
    context.UpdateObject(activityInstance);
    context.SaveChanges();
    }

The above does not work, the activity owner is defaulting to my crm user account and is not updated to reflect the owner I'm setting in activityInstance.OwnerId 

Any help would be much appreciated.
Setting OwnerId of a custom activity
===

I have created a custom CRM activity that I'm using in a workflow. 
I'm  using this activity as an InArgument to a custom workflow activity. 
In the Execute() method I'm trying to set the OwnerId of the custom CRM activity instance to a system user and calling UpdateObject(entity) on the context object that I have generated using CrmSvcUtil. 


    [Input("Some name")]
    [ReferenceEntity("mycustomactivity")]
    [Required]
    public InArgument<EntityReference> MyCustomActivity{get;set;}


    void Execute(CodeActivityContext context)
    {
    IOrganizationService svc = context.GetExtension<IOrganizationService>();
    var customActivityReference = MyCustomActivity.GetValue(MyCustomActivity);

    //MyServiceContext is an OrganizationServiceContext generated using CrmSvcUtil
    MyServiceContext servicecontext = new MyServiceContext(svc); 
    
    //GetCutomActivityInstance uses the Id to get an instance of the custom activity) 
    MyCustomCRMActivity activityInstance = GetCutomActivityInstance (servicecontext,customActivityReference.Id);

    activityInstance.OwnerId = new EntityReference("systemuser",<SomeGUID>);
    context.UpdateObject(activityInstance);
    context.SaveChanges();
    }

The above does not work, the activity owner is defaulting to my crm user account and is not updated to reflect the owner I'm setting in activityInstance.OwnerId 

Any help would be much appreciated.