DefaultInitializer Class

The DefaultInitializer extension is invoked when the user adds an object from the Toolbox to the design surface. Derive from the DefaultInitializer class to configure default initial values for your object. For example, you might add some default content to a button control or set a panel's width and height to a constant value, so that it does not collapse to zero size when it is added to the design surface. When created from the Toolbox, the element's property values appear in XAML view.

Note
Do not set default initial values in an element's constructor. The designer may not call your constructor, and in this case your default initial values are not set at design time. Instead, use the DefaultInitializer class or the ClearValue method to set default initial values.

The following code example shows how to override the InitializeDefaults method to set the default value for a Button control's Content property to "Button".

using System;

using Microsoft.Windows.Design.Model;
using Microsoft.Windows.Design.Features;

namespace DemoControlLibrary.VisualStudio.Design
{
    [Feature(typeof(ButtonDefaults))]
    public class DemoButton { }

    class ButtonDefaults : DefaultInitializer
    {
        public override void InitializeDefaults(ModelItem item)
        {
            item.Content.SetValue("Button");
        }
    }
}

Reference

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