How can I change the base class for a .NET MAUI ContentPage?

Question

Assume I have some common utilities for all of my pages so I want to abstract out a base class for all my content pages to derive from. The problem is that a newly created content page is naturally defined as partial and I can't simply change the code-behind part to use the new base class. The compiler will complain: Partial declarations of 'NewPage1' must not specify different base classes CS0263.

Answer 1

As the error suggest, your NewPage1 can't specify two different base classes . You are specifying BasePage in NewPage1.xaml.cs and by default NewPage1.xaml have ContentPage page specified as base class.

You should set the same base class in xaml also

<local:BasePage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             x:Class="MyProject.Views.NewPage1"
             xmlns:local="clr-namespace:MyProject"
             >
    <VerticalStackLayout>
        <Label 
            Text="Welcome to .NET MAUI!"
            VerticalOptions="Center" 
            HorizontalOptions="Center" />
    </VerticalStackLayout>
</local:BasePage>