一、MessageBox的Buttons
MessageBox.Show可以出现有按钮的对话框
例如:
 DialogResult dr = MessageBox.Show("是否要继续吗?", "警告!!!", MessageBoxButtons.OKCancel);//它弹出的对话框如下图所示
            if (dr == DialogResult.OK)//只有按下确定按钮才执行下面
            {
                label1.Text = "天气不错";
            }

除此之外MessageBoxButtons还有好几种对话框
二、三级联动
三个Combobox
 public Form1()// Form1的构造函数
        {
            InitializeComponent();
            AreaDataBind(comboBox1, "0001");
            AreaDataBind(comboBox2, comboBox1.SelectedValue.ToString());
            AreaDataBind(comboBox3, comboBox2.SelectedValue.ToString());
        }
 public void AreaDataBind(ComboBox cb, string Pcode)
        {
            cb.DataSource = new ChinaData().Select(Pcode);//数据源
            cb.DisplayMember = "AreaName";//显示值
            cb.ValueMember = "AreaCode";//实际值
        }
        private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
        {
            AreaDataBind(comboBox2, comboBox1.SelectedValue.ToString());
        }
        private void comboBox2_SelectedIndexChanged(object sender, EventArgs e)
        {
            AreaDataBind(comboBox3, comboBox2.SelectedValue.ToString());
        }
DateTime类型比较大小:
原文:http://www.cnblogs.com/zblc2016/p/5910595.html