Xamarin.Forms - Style Inheritance

Introduction

Xamarin.Forms code runs on multiple platforms - each of which has its own filesystem. This means that reading and writing files is most easily done using the native file APIs on each platform. Alternatively, embedded resources are a simpler solution to distribute data files with an app.

Style Inheritance

Style inheritance is performed by setting the Style.BasedOn property to an existing Style. In XAML, this is achieved by setting the BasedOn property to a StaticResource markup extension that references a previously created Style.

Prerequisites

• Visual Studio 2017 or later (Windows or Mac)

Setting up a Xamarin.Forms Project

Start by creating a new Xamarin.Forms project. You wíll learn more by going through the steps yourself.

Create a new or existing Xamarin forms(.Net standard) Project. With Android and iOS Platform. 

BaseStyle

Now, I'm going to create the base style for buttons in App.Xaml. I just add common things for the button. so that we can inherit this base style into another button style by using the BasedOn property.

App.Xaml

<?xml version="1.0" encoding="utf-8"?>
<Application xmlns="http://xamarin.com/schemas/2014/forms" xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" xmlns:d="http://xamarin.com/schemas/2014/forms/design" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" mc:Ignorable="d" x:Class="XamarinApp.App">
    <Application.Resources>

        <Style x:Key="BaseButtonStyle" TargetType="Button">
               <Setter Property="TextColor" Value="White" />
               <Setter Property="BorderWidth" Value="1" />
               <Setter Property="BorderColor" Value="Blue" />
               <Setter Property="FontSize" Value="20" />

        </Style>

     </Application.Resources>
</Application>

Style Inheritance - RedButtonStyle

Here, I'm going to inherit the BaseButtonStyle style into the RedbuttonStyle in App.Xaml. See below example

RedButtonStyle.xaml

<?xml version="1.0" encoding="utf-8"?>
<Application xmlns="http://xamarin.com/schemas/2014/forms" xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" xmlns:d="http://xamarin.com/schemas/2014/forms/design" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" mc:Ignorable="d" x:Class="XamarinApp.App">
    <Application.Resources>

        <Style x:Key="BaseButtonStyle" TargetType="Button">
               <Setter Property="TextColor" Value="White" />
               <Setter Property="BorderWidth" Value="1" />
               <Setter Property="BorderColor" Value="Blue" />
               <Setter Property="FontSize" Value="20" />

        </Style>

        <Style x:Key="RedButtonStyle" TargetType="Button"
            BasedOn="{StaticResource BaseButtonStyle}"> 
            <Setter Property="BackgroundColor" Value="Red" />
         </Style>

    </Application.Resources>
</Application>

GreenButtonStyle

Here, I'm going to inherit base BaseButtonStyle into the RedbuttonStyle in App.Xaml. See below example

GreenButtonStyle.xaml

<?xml version="1.0" encoding="utf-8"?>
<Application xmlns="http://xamarin.com/schemas/2014/forms" xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" xmlns:d="http://xamarin.com/schemas/2014/forms/design" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" mc:Ignorable="d" x:Class="XamarinApp.App">
    <Application.Resources>

        <Style x:Key="BaseButtonStyle" TargetType="Button">
               <Setter Property="TextColor" Value="White" />
               <Setter Property="BorderWidth" Value="1" />
               <Setter Property="BorderColor" Value="Blue" />
               <Setter Property="FontSize" Value="20" />

        </Style>

        <Style x:Key="GreenButtonStyle" TargetType="Button"
            BasedOn="{StaticResource BaseButtonStyle}"> 
            <Setter Property="BackgroundColor" Value="Green" />
         </Style>

        <Style x:Key="RedButtonStyle" TargetType="Button"
            BasedOn="{StaticResource BaseButtonStyle}"> 
            <Setter Property="BackgroundColor" Value="Red" />
         </Style>

    </Application.Resources>
</Application>

Consume Style

Now, I'm going to consume both button styles into the required buttons.

MainPage.Xaml

<?xml version="1.0" encoding="UTF-8"?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:xct="http://xamarin.com/schemas/2020/toolkit"
             x:Class="XamarinApp.LoginPage">
    <ContentPage.Resources>
    </ContentPage.Resources>
    <ContentPage.Content>
        
        <StackLayout HorizontalOptions="Fill"  Margin="50,100" VerticalOptions="Start">
            <Label Text="Style Inheritance" FontSize="Large"/>
            <Button Style="{StaticResource RedButtonStyle}" Text="Red Button"/>
            <Button Style="{StaticResource GreenButtonStyle}" Text="Green Button"/>

        </StackLayout>
    </ContentPage.Content>
</ContentPage>

Run 

See the RedButtonStyle and GreenButtonStyles working.

I hope you have understood how to implement Style Inheritance in Xamarin.Forms.
 
Thanks for reading. Please share your comments and feedback. 

Happy Coding :)