Does Bindingsource repeatedly call the value of a control parameter?

Question

I have a simple DTO class that I set as the data source of a binding source in a form.

The form contains a user control with the Value property. This property:

 [Browsable(false)] [Bindable(BindableSupport.Yes, BindingDirection.TwoWay)] public virtual T Value { get { return this.value; } set { this.value = value; } } 

When the control is bound to the binding source, the setter is called 6 times. When control is not connected, the setter is called only 2 times

In both cases, the first call occurs because there is a line in the constructor code:

 mycontrol.Value = null; 

And the last call, because I set the value. So the first and last calls are normal. However, when control is connected, why is the setter called 4 more times?