WinForms focus issue in .NET 9

[jewicht]

We have an issue when we create a WinForms form from the ribbon.

It works fine in .NET 4.8, 6.0 and 8.0:

but does not in 9.0, it types in the Excel spreadsheet below the form:

We have no idea how to debug this. Do you think it's an issue with .NET?

See this code to be able to reproduce: https://github.com/jewicht/ExcelDNA-Samples/tree/add-form-to-ribbon-example (Ribbon.sln is modified to show a form with a textbox.)

[govert]

This sounds like a problem that has been discussed from time to time. See the threads here: https://groups.google.com/g/exceldna/c/WV5P4QVzo8M/m/QioOVV8ZAwAJ https://groups.google.com/g/exceldna/c/5GWoKylgZbA/m/RhBkvqTAAAAJ

This is perhaps the most relevant suggestion https://stackoverflow.com/questions/19458721/cant-type-on-a-wpf-window-in-a-vsto-addin

The following property must be changed before showing the popup window. Globals.ThisAddIn.Application.Interactive = false; And then reset to true on close Globals.ThisAddIn.Application.Interactive = true;

I know this more as an issue with WPF, so I'm surprised that you are reporting this with WinForms. I also know this problem from previous .NET versions, maybe there has been an update to Windows Forms in .NET 9 which affects this.

[jewicht]

Thanks for the hints. To try toggling Interactive, I had to find a way to block the execution on the form creation and display, and ShowDialog() did the trick by itself.

So in the end, I had to modify from

public void OnButtonPressed(IRibbonControl control)
{
    new Form1 { Visible = true, TopMost = true };
}

to

public void OnButtonPressed(IRibbonControl control)
{
    var form = new Form1 { Visible = false, TopMost = true };
    form.ShowDialog();
}