I am working on a WinUI3 project, in the dependencies my frameworks are stated as Microsoft.NETCore.App and Microsoft.Windows.SDK.Net.Ref. I need a class to represent a rectangular geometry. I have found an already defined class: .windows.rect?view=windowsdesktop-9.0

It seems this class is within WindowsBase assembly that I have within my project under `Microsoft.NETCore.App framework, but I don't know how to reference it ,namespaces

Online it is listed under Windows Desktop 9 (which means Windows Presentation Foundation?), anyway I cannot reference this class from within my project.

Can however reference Windows.Foundation.Rect .foundation.rect?view=winrt-26100 but it misses much of the functionality I need such as IntersectsWith(Rect), Offset, etc...

Also can reference System.Drawing.Rectangle .drawing.rectangle?view=net-8.0 which is listed under .NET but in the description says is designed for Windows Forms which I heard is to be discontinued

So first, I don't understand why I can access one but not the other, also what should I do? To be honest I spent so much time trying to make sense of it all that perhaps it would be better to implement everything with my own code.

I am working on a WinUI3 project, in the dependencies my frameworks are stated as Microsoft.NETCore.App and Microsoft.Windows.SDK.Net.Ref. I need a class to represent a rectangular geometry. I have found an already defined class: https://learn.microsoft/en-us/dotnet/api/system.windows.rect?view=windowsdesktop-9.0

It seems this class is within WindowsBase assembly that I have within my project under `Microsoft.NETCore.App framework, but I don't know how to reference it https://referencesource.microsoft/#WindowsBase,namespaces

Online it is listed under Windows Desktop 9 (which means Windows Presentation Foundation?), anyway I cannot reference this class from within my project.

Can however reference Windows.Foundation.Rect https://learn.microsoft/en-us/uwp/api/windows.foundation.rect?view=winrt-26100 but it misses much of the functionality I need such as IntersectsWith(Rect), Offset, etc...

Also can reference System.Drawing.Rectangle https://learn.microsoft/en-us/dotnet/api/system.drawing.rectangle?view=net-8.0 which is listed under .NET but in the description says is designed for Windows Forms which I heard is to be discontinued

So first, I don't understand why I can access one but not the other, also what should I do? To be honest I spent so much time trying to make sense of it all that perhaps it would be better to implement everything with my own code.

• c#
• winui-3

• WinUI3, Winforms and WPF are 3 "competiting" UI framework, if you will. In general if you work with WinUI3 you don't reference assemblies from the others (PS: none of these 3 is discontinued, Winforms sticks to "old" HWND+GDI windows, WPF is XAML + DirectX9, WinUI3 is the most modern and supports other non-.NET languages like C++ but still lacks some features). Anyway the easiest way to reference System.Windows.Rect or System.Drawing.Rectangle is to create a library, reference WPF or Winforms from there and then reference this newer library from your WinUI3 project. – Simon Mourier Commented Nov 15, 2024 at 19:51
• See this for more background on WinUI3 thomasclaudiushuber/2021/02/05/… – Simon Mourier Commented Nov 15, 2024 at 19:53
• As I said, Windows.Foundation.Rect and System.Drawing.Rectangle, are accessible. I really want is to reference the Rect in WindowsBase and I feel I am really close. I would assume that this assembly System.Windows namespace is overshadowed by the same namespace from other assemblies within the framework. But, I can't figure out how can i access it. Thanks for the link – Eliy Arlev Commented Nov 15, 2024 at 20:02
• In "WinUI", one uses the Microsoft.UI.Xmal.Shapes.Rectangle for "drawing"; and can use the Windows.Foundation.Rect for "geometry". The method in question is "Intersect"; not "IntersectsWith". A further clue is that WinUI uses the "Foundation.Point" versus the "Drawing.Point". I use the FrameworkElement (Canvas left, top; Width and Height) to create the corresponding Rect when I need it. (Add it as an extension method, for example). – Gerry Schmitz Commented Nov 15, 2024 at 20:45
• 1 Re-read what I said. Add a class library project with <TargetFramework>net8.0-windows</TargetFramework> for example and <UseWPF>true<UseWPF> in it, reference that project from your WinUI3 project and you will be able to use System.Windows.Rect from WindowsBase. I never mentioned Windows.Foundation.Rect. – Simon Mourier Commented Nov 16, 2024 at 5:17

1 Answer 1

as Simon Mourier Commented the solution was to add <UseWPF>true</UseWPF> to .csproj project file

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>net8.0-windows10.0.19041.0</TargetFramework>
    <TargetPlatformMinVersion>10.0.17763.0</TargetPlatformMinVersion>
    <UseWPF>true</UseWPF>

However it breaks the project as WinUI auto generated code didn't work propertly.

Was related to How can I reference WindowsBase in .Net5?