WPF_BlockEditor/ColorfulEditor/MainWindow.xaml

<Window x:Class="ColorfulEditor.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:cc="clr-namespace:ColorfulEditor.CustomControl"
        xmlns:local="clr-namespace:ColorfulEditor"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <cc:MessageBlock/>
</Window>