Question

I’ve tried MSDN but there is not an example for deriving from Freezable.

Update:

Yes in the MSDN there’s an example with animations but it’s too complicated.
need something simpler to understand freezable.

Answer 1

Documentation

In the MSDN documentation of the Freezable class, in the Remarks section, you can find the following paragraph:

For information on using and creating your own Freezable objects, see Freezable Objects Overview.

This overview contains a section Creating Your Own Freezable Class, which contains the theoretical background for what you want to do. To find an example, follow the link at the bottom of that section:

For an example of a custom Freezable class, see the Custom Animation Sample.

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Example

Since you specifically asked for a simple example, here is one (adapted from the MSDN page of Freezable.CreateInstanceCore). Remember the following sentence from the theory page:

Every Freezable subclass must override the CreateInstanceCore method. If your class uses dependency properties for all its data, you’re finished.

Let’s say we make a custom class MySimpleColor, which has exactly one boolean property IsRed. To make this class Freezable, we just have to override CreateInstanceCore:

public class MySimpleColor : Freezable
{
    // Here are your properties
    public static readonly DependencyProperty IsRedProperty = 
        DependencyProperty.Register("IsRed", typeof(Boolean), typeof(MySimpleColor));

    // CLR accessor of your property
    public bool IsRed {
        get { return (bool)GetValue(IsRedProperty); }
        set { SetValue(IsRedProperty, value); }
    }

    // All that's needed to make this Freezable
    protected override Freezable CreateInstanceCore() {
        return new MySimpleColor();      
    }
}

That’s it. The code inherited from Freezable ensures that the Freezable methods such as Freeze() or Clone() work exactly as intended.