Error using DialogResult.OK in OpenFileDialog

Question

I copied a OpenFileDialog from one of my other projects but it does not work on the new project.

 OpenFileDialog open = new OpenFileDialog();
        open.Filter = "Binary|*.bin";
        open.RestoreDirectory = true;
        open.Multiselect = false;
        try
        {
            if (open.ShowDialog() == System.Windows.Forms.DialogResult.OK)
            {
               //some code
            }
        }...

The Error says that I'm missing a reference. So i tried to configure the references, but when i click the checkbox for System.Windows.Forms it says that I can not use it because the ActiveX-Library was importet from a .NET-Assembly and that it can not be added. In my previous project i added the reference and everything works fine. How can i add a reference to a .NET-Assembly?

Bonus: Why is this happening? Is there any reason why adding a reference should be blocked within VisualStudio?

-Edit- It is a WPF-App and I am using VisualStudio 2017 with .NET Framework 4.5.2

Answer 1

Try replacing the winform reference with false.

Change this

if (open.ShowDialog() == System.Windows.Forms.DialogResult.OK)

to this

if (open.ShowDialog() == true)