Progect/DiagramPage.xaml

<Page x:Class="WpfApp1.DiagramPage"
      xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
      xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
      xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
      xmlns:local="clr-namespace:WpfApp1"
      mc:Ignorable="d" 
      d:DesignHeight="450" d:DesignWidth="800"
      Title="DiagramPage">

    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="75"/>
            <RowDefinition Height="*"/>
            <RowDefinition Height="75"/>
        </Grid.RowDefinitions>
        <Image Source="/Resources/logo.png" Margin="541,0,3,0"/>
        <Grid Background="#FF90D5FF" Panel.ZIndex="-2"></Grid>
        <Grid Grid.Row="2" Background="#FF90D5FF"></Grid>
        <Frame NavigationUIVisibility="Hidden" ContentRendered="MainFrame_ContentRendered" Grid.Row="1" Name="MainFrame"></Frame>
        <StackPanel Orientation="Horizontal" HorizontalAlignment="Center">
            <Button Content="Экспорт в Excel" Width="175" x:Name="BtnExportToExcel" Click="BtnExportToExcel_Click"/>
        </StackPanel>
    </Grid>
</Page>