Question

I have a control, with a certain property that requires a somewhat heavy init routine be called every time the property is changed.

Of course, the public property isn’t required to be set initially, but the init routine must be called with a default value.

How can I structure this, so that the init routine is only called once, regardless of whether the designer set the property or not?

Currently, it is called once in the constructor, and then again when the property setter is called through designer code (if specified). What’s a good way of dealing with this?

Answer 1

If you place the DefaultValueAttribute in front of your property, specifying the actual default value of your property, the windows forms designer will not generate code that initializes the property

[DefaultValue(0)]
private int _myProperty;
public int MyProperty { 
    get { return _value; }
    set
    {
        if (value !=  _myProperty) {
             _myProperty = value;
             HeavyInitialization();
        }
    }
}

Properties are only initialized in InitializeComponent(); if the value specified in the properties window differs from the specified default value.

If you do not need to set this property in the properties window at all, then you can hide it from the properties window with the BrowsableAttribute. You can disable serialization (code generation for InitializeComponent) completely with the DesignerSerializationVisibilityAttribute.

[Browsable(false)]
[DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)]
public int MyProperty {
    ...
}