When the custom control is present within the same project where you are going to use it, you need to add the XMLNS attribute in the following way:
xmlns:controls="clr-namespace:CH05.SearchControl"
This is the same way we added it in the preceding example. The clr-namespace defines the namespace where the controls are available. A single namespace can have one or more controls.
When the custom control is present in a different project to the one where you are going to add it, you need to add the XMLNS attribute in the following way:
xmlns:controls="clr-namespace:CH05.SearchControl;assembly=CH05.SearchControlDemo"
Here, the clr-namespace defines the namespace of the controls, whereas the assembly defines the fully qualified name of the assembly where the control is present.