Add article, snippets, toc, and redirects (#1233)

dotnet-desktop-guide/net/wpf/properties/snippets/dependency-property-security/csharp/app.xaml

@@ -0,0 +1,9 @@
+<Application x:Class="CodeSampleCsharp.App"
+             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+             xmlns:local="clr-namespace:CodeSampleCsharp"
+             StartupUri="MainWindow.xaml">
+    <Application.Resources>
+         
+    </Application.Resources>
+</Application>