How to make mdichild load at the center of mdiparent window

Answer 1

I tried showing the child with the MDI container form as owner, but caused an exception for me. You could manually set the location before showing the child as follows:

Form2 f = new Form2();
f.MdiParent = this;
f.StartPosition = FormStartPosition.Manual;
f.Location = new Point((this.ClientSize.Width - f.Width) / 2,
                       (this.ClientSize.Height - f.Height) / 2);
f.Show();

EDIT:

f.StartPosition = FormStartPosition.CenterScreen;

is the correct way to center an mdichild on its parent form.

Answer 2

I experimented a bit with this, and first came to the same solution as Patrick. But I was bugged by the following statement in the documentation of the StartPosition property:

You can also position the form to display in the center of the screen or in the center of its parent form for forms such as multiple-document interface (MDI) child forms.

So, I decided that there must be a way. And there is, though I don't find it all intuitive: set the StartPosition to CenterScreen (not CenterParent):

MdiChildUI form = new MdiChildUI();
form.MdiParent = this;
form.StartPosition = FormStartPosition.CenterScreen;
form.Show();

Of course, you can also set it in the designer instead of in code.

Answer 3

Setting start position as center screen works perfect for me.