using System;
using System.ComponentModel;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Media;

namespace MyControls
{
     public class MyControlTitleContent : Control
     {
          // dependency properties
          public static readonly DependencyProperty MyTitleProperty = DependencyProperty.Register(nameof(MyTitle), typeof(string),
               typeof(MyControlTitleContent), new FrameworkPropertyMetadata(string.Empty, FrameworkPropertyMetadataOptions.Inherits));

          public static readonly DependencyProperty MyTextProperty = DependencyProperty.Register(nameof(MyText), typeof(string),
               typeof(MyControlTitleContent), new FrameworkPropertyMetadata(string.Empty, FrameworkPropertyMetadataOptions.Inherits));

          public static readonly DependencyProperty MyBackgroundProperty = DependencyProperty.Register(nameof(MyBackground), typeof(Brush),
               typeof(MyControlTitleContent), new FrameworkPropertyMetadata(Brushes.Gray, FrameworkPropertyMetadataOptions.AffectsRender | FrameworkPropertyMetadataOptions.AffectsMeasure));

          public static readonly DependencyProperty MyFontSizeProperty = DependencyProperty.Register(nameof(MyFontSize), typeof(double),
               typeof(MyControlTitleContent), new FrameworkPropertyMetadata(16.0, FrameworkPropertyMetadataOptions.AffectsRender | FrameworkPropertyMetadataOptions.AffectsMeasure));

          // properties
          [Bindable(true)]
          [Category("Data"), Description("My title")]
          public string MyTitle
          {
               get => (string)GetValue(MyTitleProperty);
               set => SetValue(MyTitleProperty, value);
          }

          [Bindable(true)]
          [Category("Data"), Description("My text")]
          public string MyText
          {
               get => (string)GetValue(MyTextProperty);
               set => SetValue(MyTextProperty, value);
          }

          [Category("Appearance")]
          public Brush MyBackground
          {
               get => (Brush)GetValue(MyBackgroundProperty);
               set => SetValue(MyBackgroundProperty, value);
          }

          [Category("Appearance")]
          public double MyFontSize
          {
               get => (double)GetValue(MyFontSizeProperty);
               set => SetValue(MyFontSizeProperty, value);
          }

          // constructor
          static MyControlTitleContent()
          {
               DefaultStyleKeyProperty.OverrideMetadata(typeof(MyControlTitleContent), new FrameworkPropertyMetadata(typeof(MyControlTitleContent)));
          }
     }
}

<ResourceDictionary
     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
     xmlns:local="clr-namespace:MyControls">

     <ControlTemplate x:Key="My.Element.TitleContent" TargetType="local:MyControlTitleContent">

          <Border BorderThickness="1" BorderBrush="Black">
               <Grid>
                    <Grid.RowDefinitions>
                         <RowDefinition Height="Auto" />
                         <RowDefinition Height="*" />
                    </Grid.RowDefinitions>

                    <!-- show title -->
                    <TextBlock
                         Text="{TemplateBinding MyTitle}"
                         FontSize="{TemplateBinding MyFontSize}">
                    </TextBlock>

                    <!-- show text -->
                    <Border Grid.Row="1" BorderThickness="0 1 0 0" BorderBrush="Black" Background="{TemplateBinding MyBackground}">
                         <TextBlock
                              Text="{TemplateBinding MyText}"
                              FontSize="{TemplateBinding MyFontSize}">
                         </TextBlock>
                    </Border>

               </Grid>

          </Border>
     </ControlTemplate>

</ResourceDictionary>

<Window x:Class="WpfAppMyControl.MainWindow"
          xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
          xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
          xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
          xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
          xmlns:local="clr-namespace:MyControls"
          mc:Ignorable="d"
          Title="MainWindow" Height="450" Width="800">
    
     <!-- add my library -->
     <Window.Resources>
          <ResourceDictionary>
               <ResourceDictionary.MergedDictionaries>
                    <ResourceDictionary Source="Themes/Generic.xaml"/>
               </ResourceDictionary.MergedDictionaries>
          </ResourceDictionary>
     </Window.Resources>

     <StackPanel Orientation="Horizontal">

          <!-- my control -->
          <local:MyControlTitleContent
          Template="{StaticResource My.Element.TitleContent}"
               MyTitle="My books"
               MyText="Fantastic, Science"
               Width="260" Height="100"
               MyBackground="Yellow"
               MyFontSize="16">
          </local:MyControlTitleContent>

          <!-- my control -->
          <local:MyControlTitleContent
          Template="{StaticResource My.Element.TitleContent}"
               MyTitle="My films"
               MyText="'House with animals'"
               Width="220" Height="100"
               MyBackground="LightGreen"
               MyFontSize="16"
               Margin="5">
          </local:MyControlTitleContent>

     </StackPanel>
</Window>