Content update - Read-only dependency properties (user story 1878471) (#1230)

* Improve collection-type dp snippets that are readonly.

* Add article, snippets, toc, and redirects

* Minor edit

* Update target framework to .NET 6.0

dotnet-desktop-guide/net/wpf/properties/snippets/read-only-dependency-properties/vb/Application.xaml

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

dotnet-desktop-guide/net/wpf/properties/snippets/read-only-dependency-properties/vb/Application.xaml.vb

@@ -0,0 +1,6 @@
+Class Application
+
+    ' Application-level events, such as Startup, Exit, and DispatcherUnhandledException
+    ' can be handled in this file.
+
+End Class

dotnet-desktop-guide/net/wpf/properties/snippets/read-only-dependency-properties/vb/AssemblyInfo.vb

@@ -0,0 +1,11 @@
+Imports System.Windows
+
+'The ThemeInfo attribute describes where any theme specific and generic resource dictionaries can be found.
+'1st parameter: where theme specific resource dictionaries are located
+'(used if a resource is not found in the page,
+' or application resource dictionaries)
+
+'2nd parameter: where the generic resource dictionary is located
+'(used if a resource is not found in the page,
+'app, and any theme specific resource dictionaries)
+<Assembly: ThemeInfo(ResourceDictionaryLocation.None, ResourceDictionaryLocation.SourceAssembly)>

dotnet-desktop-guide/net/wpf/properties/snippets/read-only-dependency-properties/vb/CodeSampleVb.vbproj

@@ -0,0 +1,22 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>WinExe</OutputType>
+    <TargetFramework>net6.0-windows</TargetFramework>
+    <RootNamespace>CodeSampleVb</RootNamespace>
+    <UseWPF>true</UseWPF>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Import Include="System.Windows" />
+    <Import Include="System.Windows.Controls" />
+    <Import Include="System.Windows.Data" />
+    <Import Include="System.Windows.Documents" />
+    <Import Include="System.Windows.Input" />
+    <Import Include="System.Windows.Media" />
+    <Import Include="System.Windows.Media.Imaging" />
+    <Import Include="System.Windows.Navigation" />
+    <Import Include="System.Windows.Shapes" />
+  </ItemGroup>
+
+</Project>

dotnet-desktop-guide/net/wpf/properties/snippets/read-only-dependency-properties/vb/MainWindow.xaml

@@ -0,0 +1,12 @@
+<Window x:Class="CodeSampleVb.MainWindow"
+    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+        Title="Readonly dependency properties" Height="100" Width="400">
+
+    <StackPanel>
+        
+        <Button Click="Button_Click">Increment property value</Button>
+        <Label Name="lblFishCount" Content="Aquarium fish count: 0"/>
+
+    </StackPanel>
+</Window>

dotnet-desktop-guide/net/wpf/properties/snippets/read-only-dependency-properties/vb/MainWindow.xaml.vb

@@ -0,0 +1,47 @@
+Namespace CodeSampleVb
+
+    ' <summary>
+    ' Interaction logic for MainWindow.xaml.
+    ' </summary>
+    Partial Public Class MainWindow
+        Inherits Window
+
+        ReadOnly _aquarium As New Aquarium()
+
+        Public Sub New()
+            InitializeComponent()
+        End Sub
+
+        Private Sub Button_Click(sender As Object, e As RoutedEventArgs)
+            ' Test setting a value.
+            _aquarium.SetValue(Aquarium.FishCountPropertyKey, _aquarium.FishCount + 1)
+            lblFishCount.Content = $"Aquarium fish count: {_aquarium.FishCount}"
+        End Sub
+
+    End Class
+
+    '<RegisterReadOnlyDependencyProperty>
+    Public Class Aquarium
+        Inherits DependencyObject
+
+        ' Register a dependency property with the specified property name,
+        ' property type, owner type, And property metadata.
+        ' Assign DependencyPropertyKey to a nonpublic field.
+        Friend Shared ReadOnly FishCountPropertyKey As DependencyPropertyKey =
+            DependencyProperty.RegisterReadOnly(
+                name:="FishCount",
+                propertyType:=GetType(Integer),
+                ownerType:=GetType(Aquarium),
+                typeMetadata:=New FrameworkPropertyMetadata())
+
+        ' Declare a public get accessor.
+        Public ReadOnly Property FishCount As Integer
+            Get
+                Return GetValue(FishCountPropertyKey.DependencyProperty)
+            End Get
+        End Property
+
+    End Class
+    '</RegisterReadOnlyDependencyProperty>
+
+End Namespace