CatProejct/CatProject/MainWindow.xaml

<Window x:Class="CatProject.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:CatProject"
        mc:Ignorable="d"
        Title="MainWindow" Height="550" Width="1000" FontSize="28"> 
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="50"></RowDefinition>
            <RowDefinition></RowDefinition>
            <RowDefinition Height="50"></RowDefinition>
        </Grid.RowDefinitions>
        <TextBlock HorizontalAlignment="Center" VerticalAlignment="Center" FontWeight="Bold">КотоПриложение</TextBlock>
        <Frame Name="FrmMain" Grid.Row="1" NavigationUIVisibility="Hidden"></Frame>
    </Grid>
</Window>