Markup extension resolve value of a property at runtime. These are dynamic placeholder for attribute values in XAML. They are surrounded by curly braces (i.e {}) like StaticResource NormalBackgorundBrush}”. First identifier within a pair of curly braces is the name of extension. And all preceding are the named parameter in the form of Property=Value. Below are some of build in mark up extension ? Binding : For binding values of two properties ? TemplateBinding : For binding a control template to dependency property f control ? DynamicResource: For Auto updating lookup of resource entry ? StaticResoure: For one time lookup of resource entry ? X:Null : For returning Null ? X:Static: for resolving value of static property Example Now if you type text into textbox , as the text property changes , the bining mark up exntsion automatically updated the content of label.