子MDI表单显示在父MDI控件下方

Question

I have 2 Forms; Form1 and Form2. In Form1, there's a MenuStrip and a button. When I click the button, Form2 appears below the Form1 button.

private void button1_Click(object sender, EventArgs e)
{
    Form2 frm = new Form2();
    frm.MdiParent = this;
    frm.StartPosition = FormStartPosition.CenterScreen;
    frm.WindowState = FormWindowState.Maximized;
    frm.Show();
}

Answer 1

Child forms in an MDI container always underlay other controls that are directly placed on the MDI container:

You'll see the same behavior if you move the Form underneath your menu too, although since the MenuStrip is docked, you should see scroll bars that allow you to view the entire Form.

Either merge your button onto the MenuStrip:

Or dock it to an edge somewhere: (this looks ridiculous, but it's just to demonstrate; you could dock a panel and move it in there, or play around with a ToolStrip, for example)