//關閉開啟的MDI子表單
private void tsmClose_Click(object sender, EventArgs e)
{
foreach (Form MDIChild in this.MdiChildren)
{
MDIChild.Close();
}
}
//檔案功能表的「開新檔案」項目
private void tsmNewFile_Click(object sender, EventArgs e)
{
MDIChild newChild = new MDIChild(); //建立子表單
//將目前的表單指定為newChild的MDI父表單
newChild.MdiParent = this;
//記錄子表單的數量
int count = this.MdiChildren.Length;
//設定子表單的標題
newChild.Text = $"我是子表單-{count.ToString()}";
newChild.Show(); //顯示MDI子表單
}