How can WPF objects deriving from Freezable be frozen in XAML?

To freeze a Freezable object declared in markup, you use the Freeze attribute defined in XML namespace http://schemas.microsoft.com/winfx/2006/xaml/presentation/options.

In the following example, a SolidColorBrush is declared as a page resource and frozen. It is then used to set the background of a button.

<Page   xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"  xmlns:po="http://schemas.microsoft.com/winfx/2006/xaml/presentation/options"   xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"  mc:Ignorable="po">  <Page.Resources>    <!-- This brush is frozen -->    <SolidColorBrush x:Key="MyBrush" po:Freeze="True" Color="Red" />  </Page.Resources>  <!-- Use the frozen brush -->  <Button Background="{StaticResource MyBrush}">Click Me</Button></Page>

Source: Freezable Objects Overview

Add this to your xaml namespace declarations:

xmlns:po="http://schemas.microsoft.com/winfx/2006/xaml/presentation/options"xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"mc:Ignorable="po"

then, in your freezable objects, include this attribute

po:Freeze="True"