Question

If I call Close() in my WinForm, it seems that even though DialogResult is None at the time, right after I call Close() I see that it is set to Cancel.

Does this sound normal?

Answer 1

That is completely normal, as it is the intended behavior. However, it is not equivalent to clicking the red “X” in the top right corner of the Form if you are using an MDI or ShowDialog().

When a form is displayed as a modal dialog box, clicking the Close
button (the button with an X in the top-right corner of the form)
causes the form to be hidden and the DialogResult property to be set
to DialogResult.Cancel. The Close method is not automatically called
when the user clicks the Close button of a dialog box or sets the
value of the DialogResult property. Instead, the form is hidden and
can be shown again without creating a new instance of the dialog box.
Because of this behavior, you must call the Dispose method of the form
when the form is no longer needed by your application.

The DialogResult value can be overridden though:

You can override the value assigned to the DialogResult property when
the user clicks the Close button by setting the DialogResult property
in an event handler for the Closing event of the form.

http://msdn.microsoft.com/en-us/library/system.windows.forms.form.dialogresult(v=VS.100).aspx