[8.0.100-alpha.1.23056.11] Form opens multiple times when launched from UserControl with EventHandler in AutoVersionsDB App

.NET version

.NET SDK:
Version:   8.0.100-alpha.1.23056.11
Commit:    7bea0af7fe 

Runtime Environment:
OS Name:     Windows
OS Version:  10.0.19045
OS Platform: Windows
RID:         win10-x64
Base Path:   C:\Program Files\dotnet\sdk\8.0.100-alpha.1.23056.11\ 

Host:
  Version:      8.0.0-alpha.1.23055.3
  Architecture: x64
  Commit:       9197fd5551 

.NET SDKs installed:
  8.0.100-alpha.1.23056.11 [C:\Program Files\dotnet\sdk] 

.NET runtimes installed:
  Microsoft.AspNetCore.App 8.0.0-alpha.1.23055.4 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 8.0.0-alpha.1.23055.3 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.WindowsDesktop.App 8.0.0-alpha.1.23055.1 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App] 

Did it work in .NET Framework?

Yes

Did it work in any of the earlier releases of .NET Core or .NET 5+?

Yes

Verify Scenarios: 1). Windows 10 21H2 AMD64 + dotnet-sdk-8.0.100-alpha.1.23060.31: Fail 2). Windows 10 21H2 AMD64 + dotnet-sdk-8.0.100-alpha.1.23056.11: Fail 3). Windows 10 21H2 AMD64 + dotnet-sdk-8.0.100-alpha.1.23053.3: Pass 4) Windows 10 21H2 AMD64 + dotnet-sdk-7.0.102-win-x64: Pass 5). Windows 10 21H2 AMD64 + dotnet-sdk-6.0.405-win-x64: Pass 6). Windows 10 21H2 AMD64 + dotnet-sdk-5.0.505-win-x64: Pass

Issue description

When testing the 3rd party app AutoVersionsDB with latest .NET 8 runtime, Form opens multiple times when launched from UserControl with EventHandler.

Application Name: AutoVersionsDB OS: Windows 10 21H2 CPU: X64 .NET Build Number: dotnet-sdk-8.0.100-alpha.1.23056.11 App or App Source checking at: https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1716419 Github Link: https://github.com/modi-w/AutoVersionsDB

Steps to reproduce

The machine only has 8.0 installed. And DOTNET_ROLL_FORWARD_ON_NO_CANDIDATE_FX=2 is set.

1.Launch application from “%app_client_root%\AutoVersionsDB\AutoVersionsDB.WinApp.exe”.
2.Click “New Project” button.
3.Type “test” in Id. 4.Click “Save” button. ( if you receive errors, ignore) 5.Click “Menu” icon. 6.Click “DB Process” button. 7.Click “add” button. 8.Click Cancel

Expected Result: Input box should close Actual Result: Input box closes and opens again

Minimal Repro Steps: Minimal repro sample attached: 2605123.zip

1. Create WinForms App, change the form name to MainForm
2. Create UserContol, and add this code, also add drag a button to control (button1)

 public partial class UserControl1 : UserControl  //not repro when it is inherit from Form
    {
        MyClass obj = new MyClass();
        public UserControl1()
        {
            InitializeComponent();
        }
        protected override void OnLoad(EventArgs e)
        {
            base.OnLoad(e);
            obj.TestEvent += _OnTestEvent; //if we move this line to constructor, not repro
        }
        private void _OnTestEvent(object sender, EventArgs e)
        {
            Form2 fmr = new Form2();
            fmr.ShowDialog();
        }
        private void button1_Click(object sender, EventArgs e)
        {
            obj.OpenForm();
        }
    }
    public class MyClass
    {
        public event EventHandler<EventArgs> TestEvent;
        public void OpenForm()
        {
            var eventsArgs = new EventArgs();
            TestEvent(this, eventsArgs);
        }
    }

1. Add UserContol to MainForm
2. Create another Form for popup window (Form2 )
3. Add this code to close the from

public partial class Form2 : Form
    {
        public Form2()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            this.Close();
        }
    }

1. Build and launch the app
2. Click button to open window
3. Close the window

Excepted Result: Pop Up window should close Actual Result: (when we run in NET8, it works when we run on previous versions) Window close and open again

Findings: When we move this line obj.TestEvent += _OnTestEvent; to constructor, issue not repro This issue only repro when we attach EventHandler in UserControl, not repro with Forms.

@dotnet-actwx-bot @dotnet/compat

[MelonWang1]

Verified on latest .NET 8.0.100-preview.2.23123.5 build, issue is fixed. No ‘reopening’ behavior. Screenshot as below:

[Nora-Zhou01]

Verified this on .NET 8.0 Preview 2.0 TP build: 8.0.100-preview.2.23151.8, issue was fixed. No ‘reopening’ behavior. Test result is same as above screenshot.