Error

 #ERASE ALL THIS AND PUT XAML BELOW between the @" "@
$inputXML = @"
<Window x:Class="WpfApp1.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:WpfApp1;assembly=WpfApp1Assembly"
        mc:Ignorable="d"
        Title="HG Folder &amp; Permission Deployment" Height="350" Width="525">
    <Grid RenderTransformOrigin="0.511,0.507" Background="{x:Null}">
        <Image HorizontalAlignment="Left" Height="100" Margin="10,10,0,0" Name="Image" VerticalAlignment="Top" Width="70" Source="C:\Users\jfitzgerald\Pictures\img1.jpg"/>
        <TextBlock HorizontalAlignment="Left" Margin="115,10,0,0" Name="TextBlock" TextWrapping="Wrap" Text="This useful tool is a front end for a powerful PowerShell script that will allow you to deploy a propertie's folder and subfolders, with the proper permissions, in the Review drive." VerticalAlignment="Top" Height="97" Width="392"/>
        <Button Content="OK" HorizontalAlignment="Left" Name="Button" Margin="432,289,0,0" VerticalAlignment="Top" Width="75"/>
        <Label Content="Username&#xD;&#xA;" Name="Label" HorizontalAlignment="Left" Margin="81,172,0,0" VerticalAlignment="Top" RenderTransformOrigin="0.5,0.5" Width="63" Height="26"/>
        <TextBox HorizontalAlignment="Left" Name="TextBox" Height="23" Margin="158,175,0,0" TextWrapping="Wrap" Text="Enter Your Username" VerticalAlignment="Top" Width="120" RenderTransformOrigin="0.499,0.456"/>

    </Grid>
</Window>
"@

$inputXML = $inputXML -replace 'mc:Ignorable="d"','' -replace "x:N",'N' -replace '^<Win.*', '<Window'

[void][System.Reflection.Assembly]::LoadWithPartialName('presentationframework')
[xml]$XAML = $inputXML

#Read XAML

    $reader=(New-Object System.Xml.XmlNodeReader $xaml)
try{$Form=[Windows.Markup.XamlReader]::Load( $reader )}
catch{Write-Warning "Unable to parse XML, with error: $($Error[0])`n Ensure that there are NO SelectionChanged properties (PowerShell cannot process them)"
    throw}

#===========================================================================
# Load XAML Objects In PowerShell
#===========================================================================

$xaml.SelectNodes("//*[@Name]") | %{"trying item $($_.Name)";
    try {Set-Variable -Name "WPF$($_.Name)" -Value $Form.FindName($_.Name) -ErrorAction Stop}
    catch{throw}
    }

Function Get-FormVariables{
if ($global:ReadmeDisplay -ne $true){Write-host "If you need to reference this display again, run Get-FormVariables" -ForegroundColor Yellow;$global:ReadmeDisplay=$true}
write-host "Found the following interactable elements from our form" -ForegroundColor Cyan
get-variable WPF*
}

Get-FormVariables

#===========================================================================
# Actually make the objects work
#===========================================================================

#Sample entry of how to add data to a field

#$vmpicklistView.items.Add([pscustomobject]@{'VMName'=($_).Name;Status=$_.Status;Other="Yes"})

#===========================================================================
# Shows the form
#===========================================================================
write-host "To show the form, run the following" -ForegroundColor Cyan
'$Form.ShowDialog() | out-null'
WARNING: Unable to parse XML, with error: Exception calling "Load" with "1" argument(s): "Cannot create unknown type '{http://schemas.microsoft.com/winfx/2006/xaml/presentation}Null'."
 Ensure that there are NO SelectionChanged properties (PowerShell cannot process them)
Exception calling "Load" with "1" argument(s): "Cannot create unknown type '{http://schemas.microsoft.com/winfx/2006/xaml/presentation}Null'."
At line:30 char:5
+ try{$Form=[Windows.Markup.XamlReader]::Load( $reader )}
+     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : NotSpecified: (:) [], ParentContainsErrorRecordException
    + FullyQualifiedErrorId : XamlParseException