c# winform 窗体最大化后挡住了任务栏

this.WindowState = FormWindowState.Normal;
      this.FormBorderStyle = FormBorderStyle.Sizable;
      this.Top = 0;
      this.Left = 0;
      this.Width = Screen.PrimaryScreen.WorkingArea.Width;
      this.Height = Screen.PrimaryScreen.WorkingArea.Height;