Open WPF form from a VSTO outlook addin

So first of all there is no item called WPF Form, there is only User Control for WPF. So once the WPF UserControl is created in the XAML you notice that this is the code

<UserControl x:Class="SQL_openertak2.ServerList"
             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" 
             mc:Ignorable="d" d:DesignHeight="454" d:DesignWidth="259" SizeToContent="WidthAndHeight">
    <Grid>
        <ListBox Height="410" HorizontalAlignment="Left" Margin="12,12,0,0" Name="listBox1" VerticalAlignment="Top" Width="242" />
        <Button Content="Button" Height="23" HorizontalAlignment="Left" Margin="12,427,0,0" Name="button1" VerticalAlignment="Top" Width="75" Click="button1_Click" />
    </Grid>
</UserControl>

So i have looked thru the XAML code. So as you can see that the whole thing is USERCONTROL you have to change it to WINDOW then you will be able to see the .Show()

But take note that you also have to change the code in the xaml.cs

cause it will be like this by default

public partial class ServerList : UserControl

Change it to

public partial class ServerList : Window

well for obvious reasons!! :)