Could not load file or assembly system windows forms

ℹ️ UPDATE: Workaround here for those who need it.

. . .

There appears to be a critical problem with the new 6.0.2 update which makes apps compiled with it fail to start on machines running 6.0.1.

To reproduce, do the following:

1. Visit Windows Update to update the runtime on your dev machine, and also update Visual Studio 2022 using Visual Studio Installer.
2. On a client/test machine, install the 6.0.1 desktop runtime. Direct Link
3. On your dev machine, create a new WinForms project, build it and copy the executable files to the client/test machine.
4. Run it and it will not start. Event logs show the following:

Application: WinFormsApp1.exe
CoreCLR Version: 6.0.121.56705
.NET Version: 6.0.1
Description: The process was terminated due to an unhandled exception.
Exception Info: System.IO.FileLoadException: Could not load file or assembly 'System.Windows.Forms, Version=6.0.2.0, Culture=neutral, PublicKeyToken=b77a5c561934e089'. The located assembly's manifest definition does not match the assembly reference. (0x80131040)
File name: 'System.Windows.Forms, Version=6.0.2.0, Culture=neutral, PublicKeyToken=b77a5c561934e089'
   at WinFormsApp1.Program.Main()

This problem did not happen on .NET 5. I was under the impression patch versions are generally compatible with each other, and I use <RollForward>LatestPatch</RollForward> in my real app, but even with that setting it still crashes.

This is a blocking issue for me because if I distribute an update for my app built on 6.0.2 and the client is still running 6.0.1, that will be bad if the app suddenly stops working.

I have an NUnit test project dedicated for unit testing which has a Target Framework of .Net Core 2.1. This test project has references of two other Projects one of which is a Windows Form based application and the other is a Class Library based application for database interactions. Both of these projects has a target framework of .Net Framework 4.6.1

I am writing a test for testing a method of the Class Library based application to test the output of the method. But it’s showing the following error,

‘System.IO.FileNotFoundException : Could not load file or assembly ‘System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089′. The system cannot find the file specified.’

I have tried the following fixes and none of them worked.

• Removing the project references and adding them again
• Changing build platform target from AnyCPU to X86 and x64
• Adding dependant assemblies tag inside a .config file. (Interesting things is .NET Core 2.1 doesn’t provide with a .config file)

This is the test class (Test_DataClasses.cs),

using System;
using System.Collections.Generic;
using System.Text;
using NUnit.Framework;
using System.Data.SQLite;
using SharedDataClasses;
using MantechAutomationControl;
using System.IO;
using System.Reflection;

namespace MAC_Testing
{
[TestFixture]
class Test_DataClasses
{
    #region Tests
    [Test]
    public void t_m_initializeDatabase()
    {
        //Assign
        string v_dbLocation = Path.Combine("M:\\For_Jabed\\MAC\\MAC\\MantechAutomationControl\\bin\\Debug\\", "DB.sqlite");
        //Act
        DataClasses_v2.m_initializeDatabase();
        //Assert
        Assert.That(new FileInfo(v_dbLocation), Does.Exist);
    }
    #endregion
}
}

And this is the method the above test is trying to validate,

public static class DataClasses_v2
{
    #region Variables 
    #endregion
    #region Methods
    public static void  m_initializeDatabase()
    {
        string v_executableLocation = Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location);
        string v_dbLocation = Path.Combine(v_executableLocation, "DB.sqlite");
        if (!File.Exists(v_dbLocation))
        {
            DialogResult o_createDBFileDialogBox = MessageBox.Show("Could not find the database in the expected location:\n" + v_dbLocation + "\n\nWould you like to create a new blank database file?", "Warning", MessageBoxButtons.YesNo);
            if (o_createDBFileDialogBox == DialogResult.Yes)
            {
                SQLiteConnection.CreateFile(v_dbLocation);
                using (SQLiteConnection o_dbConnection = new SQLiteConnection(@"DataSource=" + v_dbLocation + ";Version=3;"))
                {
                    o_dbConnection.Open();
                }
            }
            else
                return;
        }
    }

I don’t really understand whats going on here. Although point to be noted I actually was working towards to use Nunit Form dll to work with Forms (DialogBox) as the method to be tested had a DialogBox to work with.

In the test project there is another class and the tests written inside those class works fine for the Same target ‘Class Library’ based project to validate a different function.

Hopefully someone will be able to explain whats going on here.

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