WPF CustomControl

Choose the right base class

UIElement	Layout, Input, Focus and Events
FrameworkElement	Style, ToolTip, ContextMenu, and etc.
Control	Template, Foreground, Background, FontSize
ContentControl	ContentProperty
HeaderedContentControl	HeaderProperty TabControl, Expander, GroupBox
ItemsControl	ItemCollection
Selector	ComboBox, ListBox, ListView, TabControl
RangeBase	Slider, ProgressBar MinimumProperty, MaximumProperty

Override the Default Style

static MyCustomControl()
{
    DefaultStyleKeyProperty.OverrideMetadata(
        typeof(MyCustomControl),
        new FrameworkPropertyMetadata(typeof(MyCustomControl));
}

Create a default Style

<ResourceDictionary
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:sys="clr-namespace:System;assembly=mscorlib"
    xmlns:sd="clr-namespace:System.Drawing;assembly=System.Drawing"
    xmlns:swm="clr-namespace:System.Windows.Media;assembly=PresentationCore">
 
    <Style TargetType="{x:Type local:MyCustomControl}">
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type local:MyCustomControl}">
                    ...
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>
 
</ResourceDictionary>

public static readonly DependencyProperty MyContentProperty =
    DependencyProperty.Register(
        nameof(MyContent),
        typeof(object),
        typeof(MyCustomControl),
        new FrameworkPropertyMetadata(
            null,
            FrameworkPropertyMetadataOptions.AffectsRender |
            FrameworkPropertyMetadataOptions.AffectsParentMeasure));
 
public object MyContent
{
    get => GetValue(MyContentProperty);
    set => SetValue(MyContentProperty, value);
}