使弹出窗体相对控件的位置固定的方法！

在点击Button弹出一个新窗体时，希望窗体位于Button的上面，改变Button位置点击新窗体的位置始终相对固定。

           BlankFrm m_listViewUI = new BlankFrm();        
            this.listBox1.Items.Clear();
            m_listViewUI.StartPosition = FormStartPosition.Manual;       
            m_listViewUI.Location = new Point(Control.MousePosition.X, Control.MousePosition.Y - 250 - 28);
            //m_listViewUI.Location = pt;
            m_listViewUI.Name = "listViewUI1";
            m_listViewUI.Padding = new System.Windows.Forms.Padding(4);
            m_listViewUI.Size = new System.Drawing.Size(200, 250);

开始用这种方法，好像有些繁琐！

            m_listViewUI = new BlankFrm();
            int x, y;
            int Screen_x = System.Windows.Forms.Screen.PrimaryScreen.WorkingArea.Size.Width;
            int Screen_y = System.Windows.Forms.Screen.PrimaryScreen.WorkingArea.Size.Height;
            this.listBox1.Items.Clear();
            m_listViewUI.StartPosition = FormStartPosition.Manual;
            Control control = (Control)sender;
            //MessageBox.Show(this.PointToClient(this.btnAdd.Location).X.ToString() + "  " + this.PointToClient(this.btnAdd.Location).Y.ToString());
            Point pt1 = control.PointToScreen((sender as Button).Location);
            x = this.PointToScreen((sender as Button).Location).X;
            y = pt1.Y - 250 - 28;
            m_listViewUI.Location = new Point(x, y);
            m_listViewUI.Name = "listViewUI1";
            m_listViewUI.Padding = new System.Windows.Forms.Padding(4);
            m_listViewUI.Size = new System.Drawing.Size(200, 250);