Dependency Property optimisation?

Question

When I set collection value from xaml within the control as such it seems to set value correctly:

Answer 1

The cause is that a local property value has higher precedence than a value from a Style Setter.

Instead of setting a local value, you could use the SetCurrentValue method:

public InjectCustomArray()
{
    InitializeComponent();
    SetCurrentValue(MyPropertyProperty, new ICustomType[0]);
}

See the Dependency Property Value Precedence article on MSDN for more details.