pluginWindow.xaml

<Window x:Class="testPlugin.myWindow"
             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:testPlugin"
             mc:Ignorable="d" 
        Closing="Window_Closing"
        Closed="Window_Closed"
        Title="My Plugin UI 2"
             Width="500">
    <TabControl>
        <TabItem Header="Event listener">
            <Grid>
                <Grid.RowDefinitions>
                    <RowDefinition Height="Auto"></RowDefinition>
                    <RowDefinition Height="*"></RowDefinition>
                    
                </Grid.RowDefinitions>
                <TextBlock TextWrapping="Wrap">Events received from main application 2: </TextBlock>
                <TextBox Name="txtLog" Margin="4,4" Grid.Row="1"></TextBox>

        
            </Grid>
        </TabItem>
        <TabItem Header="Tagging example">

            <Grid>
                <Grid.ColumnDefinitions>
                    <ColumnDefinition Width="Auto"></ColumnDefinition>
                    <ColumnDefinition Width="*"></ColumnDefinition>
                </Grid.ColumnDefinitions>
                <Grid.RowDefinitions>
                    <RowDefinition Height="Auto"></RowDefinition>
                    <RowDefinition Height="Auto"></RowDefinition>
                    <RowDefinition Height="Auto"></RowDefinition>
                    <RowDefinition Height="Auto"></RowDefinition>
                    <RowDefinition Height="*"></RowDefinition>
                </Grid.RowDefinitions>
                <TextBlock TextWrapping="Wrap">Type a tag name here</TextBlock>
                <TextBlock TextWrapping="Wrap" Grid.Row="1">Type a file name (will full path) here</TextBlock>

                <TextBox Name="txtTagName" Grid.Column="1" Margin="4">Tag 1</TextBox>
                <TextBox Name="txtFilePath" Grid.Column="1" Grid.Row="1" Margin="4">C:\users\foo\Documents\test.pdf</TextBox>
                <Button Grid.ColumnSpan="2" Name="btnTag" Grid.Row="2" Padding="4,4" Margin="4,4" Grid.Column="0" Click="btnTag_Click">Tag this file with this tag</Button>
                <Button Grid.ColumnSpan="2" Name="btnUntag" Grid.Row="3" Padding="4,4" Margin="4,4" Grid.Column="0" Click="btnUntag_Click">Untag this file from this tag</Button>
            </Grid>
            
        </TabItem>
    </TabControl>

</Window>