Show Dialog box at center of its parent

It's been a mess to show a DialogBox at the center of its parent form. Here is a method to show a dialog.

I am positioning its parent to center but not able to center the DialogBox

private void OpenForm(Object point, Object height, Object width)
{
    FormLoading frm = new FormLoading();
    Point temp = (Point)point;
    Point location = new Point(temp.X + (int)((int)width) / 2, 
                               temp.Y + (int)((int)height) / 2);
    frm.Location = location;
    frm.ShowDialog();
}

private void btnView_Click(object sender, EventArgs e)
{
    try
    {                    
        ThreadStart starter= delegate { OpenForm(currentScreenLocation, 
                                                 this.Height, this.Width); };
        Thread t = new Thread(starter);
        t.Start();
        ////// Some functionality here...
        t.Abort();
    }
    catch (Exception)
    {
    }
}