Use Windows Forms in a .Net Core Class Library - .NET Core Control Library

Question

I am trying to create a .net core 3 class library that references the .net core 3 version of winform (so this assembly can itself be referenced by a .net core 3 WinForm assembly).

A new .net core WinForm project references Microsoft.WindowsDesktop.App.WindowsForms, however I can't find any nuget package with that name.

What do I need to do to reference the .net core 3 winform?

Is "net core 3 winform" a thing? Are you trying to migrate old winforms application into .net core? — Sinatr
– Sinatr, Commented Aug 15, 2019 at 13:37
It looks very beta to me, Google say release is September 2019. Without form designer.. kek. — Sinatr
– Sinatr, Commented Aug 15, 2019 at 13:45
I am trying to write from scratch (not migrating) a WinForm helper assembly to be shared between .net core 3 WinForm applications. There is a UI to create a .net core 3 WinForm application. I just can't find a way to create a .net core 3 class assembly referencing WinForm. — Charles
– Charles, Commented Aug 15, 2019 at 13:50

Reza Aghaei · Accepted Answer · 2020-12-09 20:11:23Z

30

Update: In later versions of VS 2019 (I tried Version 16.8.2) there is a project template for Windows Forms Control Library for .NET Core.

Currently Windows Forms .NET Core is in Preview mode and I don't know any official Nuget package or Project template for Windows Forms Control Library in .NET Core in VS 2019 16.2.2.

But to create a Windows Forms Control Library, you can use the following instructions:

Add a new project of type Class Library (.NET Core)
After project created, right click on project file and choose Edit Project File
Change the project SDK to <Project Sdk="Microsoft.NET.Sdk.WindowsDesktop">
Specify windows forms as UI technology by adding <UseWindowsForms>true</UseWindowsForms>.

Now the project file should be like the following:

<Project Sdk="Microsoft.NET.Sdk.WindowsDesktop">
  <PropertyGroup>
    <OutputType>Library</OutputType>
    <TargetFramework>netcoreapp3.0</TargetFramework>
    <UseWindowsForms>true</UseWindowsForms>
  </PropertyGroup>
</Project>

Now you can add Windows forms elements like Form or UserControl to this project and build the project without any problem.

edited Dec 9, 2020 at 20:11

answered Aug 15, 2019 at 16:25

Reza Aghaei

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13 Comments

Reza Aghaei Over a year ago

If for some reason you are looking for dlls, you can find them in C:\Program Files\dotnet\packs\Microsoft.WindowsDesktop.App.Ref\3.0.0-preview6-27626-01\ref\netcoreapp3.0 (depending to installed version of the framework).

Charles Over a year ago

I tried your suggestion but the "System.Windows.Forms" namespace isn't made available in that project.

JRB Over a year ago

Hello Reza, great answer and it's working for netcoreapp3.0. I had the feeling i had to close visual studio once before it started working. Do you know a way to also have it work for .netstandard2.0 and .netstandard2.1. I haven't been able to do that yet.

pushkin Over a year ago

@JRB Did you ever figure out how to do this with Standard 2.1?

pushkin Over a year ago

@JRB Thanks for the update. That does appear to be the right thing to do to get winforms to work; class assembly for core not standard

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Russell Munro · Accepted Answer · 2021-06-10 03:14:00Z

10

I had a core 3.1 web app referring to a Framework 4.5.2 project that had dependencies on System.Windows.Forms. The fix for me was to add the below line to web app csproj file:

FrameworkReference Include="Microsoft.WindowsDesktop.App.WindowsForms"

<Project Sdk="Microsoft.NET.Sdk.Web">

  <PropertyGroup>
    <TargetFrameworks>netcoreapp3.1</TargetFrameworks>
    <UseWindowsForms>true</UseWindowsForms>
  </PropertyGroup>

  <ItemGroup>
    <FrameworkReference Include="Microsoft.WindowsDesktop.App.WindowsForms" />
  </ItemGroup>

</Project>

edited Jun 10, 2021 at 3:14

answered Aug 11, 2020 at 0:15

Russell Munro

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Comments

J R · Accepted Answer · 2021-03-02 11:18:45Z

8

The currently accepted answer appears to be somewhat outdated. The recent syntax requires the target to be specified in the TargetFramework tag, not in the Sdk tag:

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <OutputType>Library</OutputType>
    <TargetFramework>net5.0-windows</TargetFramework>
    <UseWindowsForms>true</UseWindowsForms>
    <GenerateAssemblyInfo>false</GenerateAssemblyInfo>
  </PropertyGroup>

</Project>

More info here

answered Mar 2, 2021 at 11:18

J R

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InteXX · Accepted Answer · 2024-07-08 21:35:16Z

3

In alternative you can add a new project of Windows Form Type and then set the output type to Libray.

<OutputType>Library</OutputType>

edited Jul 8, 2024 at 21:35

InteXX

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answered May 4, 2020 at 8:24

Roberto Bergamini

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Kirsten · Accepted Answer · 2022-03-01 00:18:26Z

2

For me, with net5 I needed the following in my project

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
      <TargetFramework>net5.0-windows</TargetFramework>
      <UseWindowsForms>true</UseWindowsForms>
  </PropertyGroup>

answered Mar 1, 2022 at 0:18

Kirsten

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