[Breaking change]: Crashes due to incorrect usage of DyanmicResource's (#46093)

* [Breaking change]: Crashes due to incorrect usage of `DyanmicResource`'s
Fixes #46089

* Remove quote that snuck in

---------

Co-authored-by: Andy (Steve) De George <[email protected]>

Author: Cam Soper

docs/core/compatibility/10.0.md

@@ -81,3 +81,9 @@ If you're migrating an app to .NET 10, the breaking changes listed here might af
 | [Renamed parameter in HtmlElement.InsertAdjacentElement](windows-forms/10.0/insertadjacentelement-orientation.md)                             | Source incompatible | Preview 1          |
 | [TreeView checkbox image truncation](windows-forms/10.0/treeview-text-location.md)                                                            | Behavioral change   | Preview 1          |
 | [StatusStrip uses System RenderMode by default](windows-forms/10.0/statusstrip-renderer.md)                                                   | Behavioral change   | Preview 1          |
+
+## Windows Presentation Foundation (WPF)
+
+| Title                                                                                            | Type of change                        | Introduced version |
+|--------------------------------------------------------------------------------------------------|---------------------------------------|--------------------|
+| [Incorrect usage of DynamicResource causes application crash](wpf/10.0/dynamicresource-crash.md) | Source incompatible/behavioral change | Preview 4          |

docs/core/compatibility/toc.yml

@@ -78,6 +78,10 @@ items:
                 href: windows-forms/10.0/treeview-text-location.md
               - name: StatusStrip uses System RenderMode by default
                 href: windows-forms/10.0/statusstrip-renderer.md
+          - name: WPF
+            items:
+              - name: Incorrect usage of DynamicResource causes application crash
+                href: wpf/10.0/dynamicresource-crash.md         
       - name: .NET 9
         items:
           - name: Overview
@@ -2290,6 +2294,10 @@ items:
             href: winforms.md
       - name: WPF
         items:
+          - name: .NET 10
+            items:
+              - name: Incorrect usage of DynamicResource causes application crash
+                href: wpf/10.0/dynamicresource-crash.md        
           - name: .NET 9
             items:
               - name: "'GetXmlNamespaceMaps' type change"

docs/core/compatibility/wpf/10.0/dynamicresource-crash.md

@@ -0,0 +1,55 @@
+---
+title: "Breaking change - Incorrect usage of DynamicResource causes application crash"
+description: "Learn about the breaking change in .NET 10 Preview 4 where incorrect usage of DynamicResource now causes application crashes."
+ms.date: 5/12/2025
+ai-usage: ai-assisted
+ms.custom: https://github.com/dotnet/docs/issues/46089
+---
+
+# Incorrect usage of DynamicResource causes application crash
+
+Beginning with .NET 10 Preview 4, applications using `DynamicResource` incorrectly now crash at runtime.
+
+## Version introduced
+
+.NET 10 Preview 4
+
+## Previous behavior
+
+Applications that incorrectly initialized `DynamicResource` would continue running without crashing. The values would fall back to defaults, and an `InvalidOperationException` would appear in the output.
+
+## New behavior
+
+Applications now crash with an error similar to the following:
+
+```output
+System.Windows.Markup.XamlParseException: Set property 'System.Windows.ResourceDictionary.Source' threw an exception.
+```
+
+This occurs when an incorrect resource type is used with `DynamicResource`. For example, the code snippet below causes a crash because a `SolidColorBrush` is used instead of `System.Windows.Media.Color`:
+
+```xml
+<SolidColorBrush x:Key="RedColorBrush" Color="#FFFF0000" />
+<SolidColorBrush x:Key="ResourceName" Color="{DynamicResource RedColorBrush}" />
+```
+
+## Type of breaking change
+
+This is both a [source-incompatible](../../categories.md#source-compatibility) and [behavioral](../../categories.md#behavioral-change) change.
+
+## Reason for change
+
+This change improves the performance of `DynamicResource` usage. The optimization ensures that incorrect resource initialization is caught immediately, preventing unintended behavior.
+
+## Recommended action
+
+To avoid crashes, ensure that the correct resource types are used with `DynamicResource`. For example, the following code resolves the issue by using `System.Windows.Media.Color` instead of `SolidColorBrush`:
+
+```xml
+<Color x:Key="RedColor">#FFFF0000</Color>
+<SolidColorBrush x:Key="ResourceName" Color="{DynamicResource RedColor}" />
+```
+
+## Affected APIs
+
+None.