全选和选项交互

效果描述：

实现勾选全部选项自动把全选按钮勾上；选项中有一个没有勾选，全选按钮则不勾选

       private int chFlag = 1;//记录是否触发全选事件
        //设置全选按钮状态
        private void SetCheckState()
        {
            string flag = "";
            for (int i = 0; i < lvUser.Items.Count; i++)
            {
                flag += lvUser.Items[i].Checked.ToString().ToLower();
            }
            if (!flag.Contains("true"))
            {
                chFlag = 2;
                cbAll.Checked = false;
                chFlag = 1;
            }
            if (!flag.Contains("false"))
            {
                chFlag = 1;
                cbAll.Checked = true;
            }
            if (flag.Contains("true") && flag.Contains("false"))
            {
                chFlag = 2;
                cbAll.Checked = false;
                chFlag = 1;
            }
        }

        //列表选中事件
        private void lvUser_ItemChecked(object sender, ItemCheckedEventArgs e)
        {
            chFlag = 1;
            SetCheckState();
        }

        //全选按钮事件
        private void cbAll_CheckedChanged(object sender, EventArgs e)
        {
            if (chFlag != 2)
            {
                if (lvUser.Items.Count > 0)
                {
                    if (cbAll.Checked)
                    {
                        foreach (ListViewItem item in lvUser.Items)
                        {
                            item.Checked = true;
                        }
                    }
                    else
                    {
                        foreach (ListViewItem item in lvUser.Items)
                        {
                            item.Checked = false;
                        }
                    }
                }
            }
        }