private void statisticToolStripMenuItem_Click(object sender, EventArgs e) { if (pnMain.Controls["CRStatistic"] == null) { pnMain.Controls.Clear(); CRStatistic CRStatistic = new CRStatistic(); CRStatistic.TopLevel = false; pnMain.Controls.Add(CRStatistic); CRStatistic.FormBorderStyle = System.Windows.Forms.FormBorderStyle.None; CRStatistic.Dock = DockStyle.Fill; CRStatistic.Show(); } }