In C# code, you bring a namespace into scope with the using directive.

In a XAML page, you reference a namespace with the xmlns attribute of the page. 

each XAML page is compiled into a class, and you specify the 

name of the class that is generated with the x:Class attribute of the page:

The code below shows the namespaces used by the XAML

​

<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"

             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"

             x:Class="MauiXaml.Page1"

             ...>

​

    ...

</ContentPage>

<ContentPage ...

             xmlns:controls="clr-namespace:MyCompany.Controls;assembly=MyCompany.Controls">

    ...

</ContentPage>