function MainMenu {
    cls
    [xml]$MainMenuXAML = @"
    <Window
        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"

        Title="Teams Phone Toolbox" Height="220" Width="400">
    <Window.Background>
        <RadialGradientBrush>
            <GradientStop Color="#FFCCD5EF"/>
            <GradientStop Color="#FF6677A8" Offset="2"/>
        </RadialGradientBrush>
    </Window.Background>
    <Canvas>
        <Button x:Name = "Assign_Phone_Numbers"
            Content="Assign Phone Numbers" Canvas.Left="130" Canvas.Top="17.999" HorizontalAlignment="Left" VerticalAlignment="Center" Width="140"
        />
        <Button x:Name = "Export_CSV_of_Database"
            Content="Export CSV of Database" Canvas.Left="130" Canvas.Top="69.354" Width="140" HorizontalAlignment="Center" VerticalAlignment="Top"
        />
        <Button x:Name = "Get_User_Information"
            Content="Get User Information" Canvas.Left="130" Canvas.Top="44.394" HorizontalAlignment="Center" VerticalAlignment="Top" Width="140"
        />
        <Button x:Name = "Options"
            Content="Options" Canvas.Left="130" Canvas.Top="94.314" Width="140" HorizontalAlignment="Center" VerticalAlignment="Top"
        />
        <Button x:Name = "Exit"
            Content="Exit" Canvas.Left="130" Canvas.Top="119.274" Width="140" HorizontalAlignment="Center" VerticalAlignment="Top"
        />
    </Canvas>
</Window>
"@

    $reader = (New-Object System.Xml.XmlNodeReader $MainMenuXAML)
    $window = [Windows.Markup.XamlReader]::Load($reader)
    $window.Add_Loaded({
        $screenWidth = [System.Windows.SystemParameters]::PrimaryScreenWidth
        $screenHeight = [System.Windows.SystemParameters]::PrimaryScreenHeight
        $windowWidth = $window.Width
        $windowHeight = $window.Height
        $window.Left = ($screenWidth - $windowWidth) / 2
        $window.Top = ($screenHeight - $windowHeight) / 2
    })
    $Button_Assign_Phone_Numbers = $window.FindName("Assign_Phone_Numbers")
    $Button_Export_CSV_of_Database = $window.FindName("Export_CSV_of_Database")
    $Button_Get_User_Information = $window.FindName("Get_User_Information")
    $Button_Options = $window.FindName("Options")
    $Button_Exit = $window.FindName("Exit")

    $Button_Assign_Phone_Numbers.Add_Click({
        $window.Close()
        $UserType = "User"
        GetUserUPN
    })

    $Button_Export_CSV_of_Database.Add_Click({
        $dialog = New-Object System.Windows.Forms.SaveFileDialog
        $dialog.Title = "Export CSV of Database"
        $dialog.Filter = "CSV files (*.csv)|*.csv"
        $dialog.InitialDirectory = "c:\temp\"
        $dialog.FileName = "AllNumbers.csv"
        $result = $dialog.ShowDialog()
        if ($result -eq [System.Windows.Forms.DialogResult]::OK) {
            $window.Close()
            $AllNumbers | Export-Csv $dialog.FileName -NoTypeInformation
            MainMenu
        }
    })
    $Button_Get_User_Information.Add_Click({
        $window.Close()
        $UserType = 'Info'
        GetUserUPN
    })
    $Button_Options.Add_Click({
        $window.Close()
        OptionsMenu
    })
    $Button_Exit.Add_Click({
        $window.Close()
    })

    $window.ShowDialog()
}