Merge main into live

.github/workflows/build-validation.yml

@@ -1,27 +1,12 @@
 # This is a basic workflow to help you get started with Actions
-name: Snippets 5000
+name: 'Snippets 5000'
 
 # Controls when the action will run. Triggers the workflow on push or pull request
 on:
-  pull_request:
+  pull_request_target:
     paths:
-      - "**.cs"
-      - "**.vb"
-      - "**.fs"
-      - "**.cpp"
-      - "**.h"
-      - "**.xaml"
-      - "**.razor"
-      - "**.cshtml"
-      - "**.vbhtml"
-      - "**.csproj"
-      - "**.vbproj"
-      - "**.fsproj"
-      - "**.vcxproj"
-      - "**.sln"
-      - "**global.json"
-      - "**snippets.5000.json"
     branches: '*'
+    types: [opened, synchronize, reopened]
 
 env:
   DOTNET_INSTALLER_CHANNEL: '6.0'
@@ -30,8 +15,8 @@ env:
 
 # A workflow run is made up of one or more jobs that can run sequentially or in parallel
 jobs:
-  # This workflow contains a single job called "build"
-  build:
+  # This workflow contains a single job called "build snippets"
+  build-snippets:
     # The type of runner that the job will run on
     runs-on: windows-latest
 

.openpublishing.redirection.json

@@ -548,6 +548,14 @@
         {
             "source_path": "dotnet-desktop-guide/framework/wpf/properties/how-to-override-metadata-for-a-dependency-property.md",
             "redirect_url": "/dotnet/desktop/wpf/advanced/how-to-override-metadata-for-a-dependency-property?view=netframeworkdesktop-4.8"
+        },
+        {
+            "source_path": "dotnet-desktop-guide/net/wpf/advanced/dependency-property-callbacks-and-validation.md",
+            "redirect_url": "/dotnet/desktop/wpf/properties/dependency-property-callbacks-and-validation?view=netdesktop-6.0"
+        },
+        {
+            "source_path": "dotnet-desktop-guide/framework/wpf/properties/dependency-property-callbacks-and-validation.md",
+            "redirect_url": "/dotnet/desktop/wpf/advanced/dependency-property-callbacks-and-validation?view=netframeworkdesktop-4.8"
         }
     ]
 }

dotnet-desktop-guide/net/wpf/properties/dependency-property-callbacks-and-validation.md

@@ -0,0 +1,100 @@
+---
+title: "Dependency property callbacks and validation"
+description: Learn how to implement dependency property callbacks and validation in Windows Presentation Foundation (WPF).
+ms.date: "11/11/2021"
+dev_langs:
+  - "csharp"
+  - "vb"
+helpviewer_keywords:
+  - "dependency properties [WPF], validation"
+  - "coerce-value callbacks [WPF]"
+  - "callbacks [WPF], validation"
+  - "dependency properties [WPF], callbacks"
+  - "validation of dependency properties [WPF]"
+---
+<!--The acrolinx score was 92 on 11/11/2021-->
+
+# Dependency property callbacks and validation (WPF .NET)
+
+This article describes how to define a dependency property and implement dependency property callbacks. The callbacks support value validation, value coercion, and other logic that's needed when a property value changes.
+
+## Prerequisites
+
+The article assumes a basic knowledge of dependency properties, and that you've read [Dependency properties overview](dependency-properties-overview.md). To follow the examples in this article, it helps if you're familiar with Extensible Application Markup Language (XAML) and know how to write WPF applications.
+
+## Validate-value callbacks
+
+Validate-value callbacks provide a way for you to check whether a new dependency property value is valid before it's applied by the property system. This callback raises an exception if the value doesn't meet the validation criteria.
+
+Validate-value callbacks can only be assigned to a dependency property once, during property registration. When registering a dependency property, you have the option to pass a <xref:System.Windows.ValidateValueCallback> reference to the <xref:System.Windows.DependencyProperty.Register(System.String,System.Type,System.Type,System.Windows.PropertyMetadata,System.Windows.ValidateValueCallback)> method. Validate-value callbacks aren't part of property metadata, and can't be overridden.
+
+The effective value of a dependency property is its applied value. The effective value is determined through [property value precedence](dependency-property-value-precedence.md) when multiple property-based inputs exist. If a validate-value callback is registered for a dependency property, the property system will invoke its validate-value callback on value change, passing in the new value as an object. Within the callback, you can cast the value object back to the type registered with the property system, and then run your validation logic on it. The callback returns `true` if the value is valid for the property, otherwise `false`.
+
+If a validate-value callback returns `false`, an exception is raised and the new value is not applied. Application writers must be prepared to handle these exceptions. A common use of validate-value callbacks is validating enumeration values, or constraining numeric values when they represent measurements that have limits. Validate-value callbacks are invoked by the property system in different scenarios, including:
+
+- Object initialization, which applies a default value at creation time.
+- Programmatic calls to <xref:System.Windows.DependencyObject.SetValue%2A>.
+- Metadata overrides that specify a new default value.
+
+Validate-value callbacks don't have a parameter that specifies the <xref:System.Windows.DependencyObject> instance on which the new value is set. All instances of a `DependencyObject` share the same validate-value callback, so it can't be used to validate instance-specific scenarios. For more information, see <xref:System.Windows.ValidateValueCallback>.
+
+The following example shows how to prevent a property, typed as <xref:System.Double>, being set to <xref:System.Double.PositiveInfinity> or <xref:System.Double.NegativeInfinity>.
+
+:::code language="csharp" source="./snippets/dependency-property-callbacks-and-validation/csharp/MainWindow.xaml.cs" id="ValueValidationScenario":::
+:::code language="vb" source="./snippets/dependency-property-callbacks-and-validation/vb/MainWindow.xaml.vb" id="ValueValidationScenario":::
+
+:::code language="csharp" source="./snippets/dependency-property-callbacks-and-validation/csharp/MainWindow.xaml.cs" id="TestValueValidationScenario":::
+:::code language="vb" source="./snippets/dependency-property-callbacks-and-validation/vb/MainWindow.xaml.vb" id="TestValueValidationScenario":::
+
+## Property-changed callbacks
+
+Property-changed callbacks notify you when the effective value of a dependency property has changed.
+
+Property-changed callbacks are part of dependency property metadata. If you derive from a class that defines a dependency property, or add your class as an owner of a dependency property, you can override the metadata. When overriding metadata, you have the option to provide a new <xref:System.Windows.PropertyChangedCallback> reference. Use a property-changed callback to run logic that's needed when a property value changes.
+
+Unlike validate-value callbacks, property-changed callbacks have a parameter that specifies the <xref:System.Windows.DependencyObject> instance on which the new value is set. The next example shows how a property-changed callback can use the `DependencyObject` instance reference to trigger coerce-value callbacks.
+
+## Coerce-value callbacks
+
+Coerce-value callbacks provide a way for you to get notified when the effective value of a dependency property is about to change, so that you can adjust the new value before it's applied. In addition to being triggered by the property system, you can invoke coerce-value callbacks from your code.
+
+Coerce-value callbacks are part of dependency property metadata. If you derive from a class that defines a dependency property, or add your class as an owner of a dependency property, you can override the metadata. When overriding the metadata, you have the option to provide a reference to a new <xref:System.Windows.CoerceValueCallback>. Use a coerce-value callback to evaluate new values and coerce them when necessary. The callback returns the coerced value if coercion occurred, otherwise it returns the unaltered new value.
+
+Similar to property-changed callbacks, coerce-value callbacks have a parameter that specifies the <xref:System.Windows.DependencyObject> instance on which the new value is set. The next example shows how a coerce-value callback can use a `DependencyObject` instance reference to coerce property values.
+
+> [!NOTE]
+> Default property values can't be coerced. A dependency property has its default value set on object initialization, or when you clear other values using <xref:System.Windows.DependencyObject.ClearValue%2A>.
+
+### Coerce-value and property-changed callbacks in combination
+
+You can create dependencies between properties on an element, by using coerce-value callbacks and property-changed callbacks in combination. For example, changes in one property force coercion or re-evaluation in another dependency property. The next example shows a common scenario: three dependency properties that respectively store the current value, minimum value, and maximum value of a UI element. If the maximum value changes so that it's less than the current value, the current value is then set to the new maximum value. And, if the minimum value changes so that it's greater than the current value, the current value is then set to the new minimum value. In the example, the <xref:System.Windows.PropertyChangedCallback> for the current value explicitly invokes the <xref:System.Windows.CoerceValueCallback> for the minimum and maximum values.
+
+:::code language="csharp" source="./snippets/dependency-property-callbacks-and-validation/csharp/MainWindow.xaml.cs" id="CurrentMinMaxScenario":::
+:::code language="vb" source="./snippets/dependency-property-callbacks-and-validation/vb/MainWindow.xaml.vb" id="CurrentMinMaxScenario":::
+
+## Advanced callback scenarios
+
+### Constraints and desired values
+
+If a locally set value of a dependency property is changed through coercion, the unchanged locally set value is retained as the *desired value*. If the coercion is based on other property values, the property system will dynamically reevaluate the coercion whenever those other values change. Within the constraints of the coercion, the property system will apply a value that's closest to the desired value. Should the coercion condition no longer apply, the property system will restore the desired value&mdash;assuming no higher [precedence](/dotnet/desktop/wpf/properties/dependency-property-value-precedence#dependency-property-setting-precedence-list) value is active. The following example tests coercion in the current value, minimum value, and maximum value scenario.
+
+:::code language="csharp" source="./snippets/dependency-property-callbacks-and-validation/csharp/MainWindow.xaml.cs" id="TestCurrentMinMaxScenario":::
+:::code language="vb" source="./snippets/dependency-property-callbacks-and-validation/vb/MainWindow.xaml.vb" id="TestCurrentMinMaxScenario":::
+
+Fairly complex dependency scenarios can occur when you have multiple properties that are dependent on one another in a circular manner. Technically, there's nothing wrong with complex dependencies&mdash;except that a large number of re-evaluations can reduce performance. Also, complex dependencies that are exposed in the UI might confuse users. Treat <xref:System.Windows.PropertyChangedCallback> and <xref:System.Windows.CoerceValueCallback> as unambiguously as possible, and don't over-constrain.
+
+### Cancel value changes
+
+By returning <xref:System.Windows.DependencyProperty.UnsetValue> from a <xref:System.Windows.CoerceValueCallback>, you can reject a property value change. This mechanism is useful when a property value change is initiated asynchronously, but when it's applied is no longer valid for the current object state. Another scenario might be to selectively suppress a value change based on where it originated. In the following example, the `CoerceValueCallback` calls the <xref:System.Windows.DependencyPropertyHelper.GetValueSource%2A> method, which returns a <xref:System.Windows.ValueSource> structure with a <xref:System.Windows.BaseValueSource> enumeration that identifies the source of the new value.
+
+:::code language="csharp" source="./snippets/dependency-property-callbacks-and-validation/csharp/MainWindow.xaml.cs" id="GetValueSourceScenario":::
+:::code language="vb" source="./snippets/dependency-property-callbacks-and-validation/vb/MainWindow.xaml.vb" id="GetValueSourceScenario":::
+
+## See also
+
+- <xref:System.Windows.ValidateValueCallback>
+- <xref:System.Windows.PropertyChangedCallback>
+- <xref:System.Windows.CoerceValueCallback>
+- [Dependency properties overview](dependency-properties-overview.md)
+- [Dependency property metadata](dependency-property-metadata.md)
+- [Custom dependency properties](custom-dependency-properties.md)

dotnet-desktop-guide/net/wpf/properties/how-to-override-metadata-for-a-dependency-property.md

@@ -18,7 +18,7 @@ When you derive from a class that defines a dependency property, you inherit the
 
 ## Background
 
-A class that defines a dependency property can specify its characteristics in <xref:System.Windows.PropertyMetadata> or one of its derived types, such as <xref:System.Windows.FrameworkPropertyMetadata>. Examples of those characteristics are the default value and callback references that trigger on property change and/or coercion value change. Many classes that define dependency properties, specify property metadata during dependency property registration. When metadata isn't specified during registration, the WPF property system assigns a `PropertyMetadata` object with default values. Derived classes that inherit dependency properties through class inheritance have the option to override the original metadata of any dependency property. In this way, derived classes can selectively modify dependency property characteristics to meet class requirements. When calling <xref:System.Windows.DependencyProperty.OverrideMetadata(System.Type,System.Windows.PropertyMetadata)>, a derived class specifies its own type as the first parameter, and a metadata instance as the second parameter.
+A class that defines a dependency property can specify its characteristics in <xref:System.Windows.PropertyMetadata> or one of its derived types, such as <xref:System.Windows.FrameworkPropertyMetadata>. One of those characteristics is the default value of a dependency property. Many classes that define dependency properties, specify property metadata during dependency property registration. When metadata isn't specified during registration, the WPF property system assigns a `PropertyMetadata` object with default values. Derived classes that inherit dependency properties through class inheritance have the option to override the original metadata of any dependency property. In this way, derived classes can selectively modify dependency property characteristics to meet class requirements. When calling <xref:System.Windows.DependencyProperty.OverrideMetadata(System.Type,System.Windows.PropertyMetadata)>, a derived class specifies its own type as the first parameter, and a metadata instance as the second parameter.
 
 A derived class that overrides metadata on a dependency property must do so before the property is placed in use by the property system. A dependency property is placed in use when any instance of the class that registers the property is instantiated. To help meet this requirement, the derived class should call <xref:System.Windows.DependencyProperty.OverrideMetadata%2A> within its static constructor. Overriding the metadata of a dependency property after its owner type is instantiated won't raise exceptions, but will result in inconsistent behaviors in the property system. Also, a derived type can't override the metadata of a dependency property more than once, and attempts to do so will raise an exception.
 

dotnet-desktop-guide/net/wpf/properties/snippets/dependency-property-callbacks-and-validation/csharp/App.xaml.cs

@@ -0,0 +1,11 @@
+using System.Windows;
+
+namespace CodeSampleCsharp
+{
+    /// <summary>
+    /// Interaction logic for App.xaml
+    /// </summary>
+    public partial class App : Application
+    {
+    }
+}

dotnet-desktop-guide/net/wpf/properties/snippets/dependency-property-callbacks-and-validation/csharp/AssemblyInfo.cs

@@ -0,0 +1,10 @@
+using System.Windows;
+
+[assembly: ThemeInfo(
+    ResourceDictionaryLocation.None, //where theme specific resource dictionaries are located
+                                     //(used if a resource is not found in the page,
+                                     // or application resource dictionaries)
+    ResourceDictionaryLocation.SourceAssembly //where the generic resource dictionary is located
+                                              //(used if a resource is not found in the page,
+                                              // app, or any theme specific resource dictionaries)
+)]

dotnet-desktop-guide/net/wpf/properties/snippets/dependency-property-callbacks-and-validation/csharp/CodeSampleCsharp.csproj

@@ -0,0 +1,24 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>WinExe</OutputType>
+    <TargetFramework>net5.0-windows</TargetFramework>
+    <UseWPF>true</UseWPF>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Update="Properties\Resources.Designer.cs">
+      <DesignTime>True</DesignTime>
+      <AutoGen>True</AutoGen>
+      <DependentUpon>Resources.resx</DependentUpon>
+    </Compile>
+  </ItemGroup>
+
+  <ItemGroup>
+    <EmbeddedResource Update="Properties\Resources.resx">
+      <Generator>ResXFileCodeGenerator</Generator>
+      <LastGenOutput>Resources.Designer.cs</LastGenOutput>
+    </EmbeddedResource>
+  </ItemGroup>
+
+</Project>

dotnet-desktop-guide/net/wpf/properties/snippets/dependency-property-callbacks-and-validation/csharp/MainWindow.xaml

@@ -0,0 +1,8 @@
+<Window x:Class="CodeSampleCsharp.MainWindow"
+    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+        Title="Dependency property callbacks and validation" Height="200" Width="800" Loaded="RunTests">
+    <Grid>
+        <Label x:Name="lblMessage" HorizontalAlignment="Stretch" Margin="10" VerticalAlignment="Stretch"/>
+    </Grid>
+</Window>