Pro WPF in C# 2010: Windows Presentation Foundation in .NET 4

4.2. Property Validation

When defining any sort of property, you need to face the possibility that it may be set incorrectly. With traditional .NET properties, you might try to catch this sort of problem in the property setter. With dependency properties, this isn't appropriate, because the property may be set directly through the WPF property system using the SetValue() method.

Instead, WPF provides two ways to prevent invalid values:

• ValidateValueCallback. This callback can accept or reject new values. Usually, this callback is used to catch obvious errors that violate the constraints of the property. You can supply it as an argument to the DependencyProperty.Register() method.

• CoerceValueCallback. This callback can change new values into something ...