c# CheckBox 全部选择与取消选择

protected void CheckBoxAll_CheckedChanged(object sender, EventArgs e)
{
foreach (GridViewRow gvr in GridView1.Rows)
{
CheckBox cbox = (CheckBox)gvr.FindControl("CheckAll");
cbox.Checked = this.CheckBoxAll.Checked;
this.CheckBoxAll.Text = this.CheckBoxAll.Checked ? "取消选择" : "全部选择";
}
}