Question

I have two DPs that I update in a DefiningGeometry get:

protected override Geometry DefiningGeometry
{
    get
    {
        StartSc = sc.Transform(Start);
        EndSc = sc.Transform(End);
        //Start and End are also dependencies properties.    
    ...
    }
}

I bind to StartSc and EndSc but the target never gets updated, it always stays the default value of 0. Start and End change, so that is not the issue, I am wondering if assignment in the DefiningGeometry get doesn’t have an effect on the properties. Does anyone see any obvious mistake?

Note: I had the same variables names which were hiding the DPs from a derived class, removing the hiding the above code worked, but the bellow answer works either way.

Answer 1

If you bind to DPs and you are in the control’s code you want to use SetCurrentValue (not the CLR-wrappers (StartSc & EndSc) which use SetValue) because otherwise you overwrite the existing bindings with the concrete value.

Also as i said, avoid doing things in getters, it is really hard to tell when and how often they get called.