private void 步JsonToolStripMenuItem_Click(object sender, EventArgs e) { foreach (Form f in MdiChildren) { if (f.Name == "FrmJsonFilesWatcher") { f.Visible = true; f.Activate(); f.WindowState = FormWindowState.Maximized; return; } } FrmJsonFilesWatcher fm = new FrmJsonFilesWatcher(); fm.MdiParent = this; fm.WindowState = FormWindowState.Maximized; fm.Show(); }