通过拼接SQL字符串实现多条件查询

一、通过拼接SQL字符串的方法的好处是：

1、方便查询条件的扩展。

2、简化业务逻辑的判断。

二、例子：

1、界面设计

2、点击查询的代码

        /// <summary>
        /// 按条件查询
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void BtSearch_Click_1(object sender, EventArgs e)
        {
            List<string> wherelist = new List<string>();
            List<SqlParameter> parametlist = new List<SqlParameter>();
            
            if (CbMzh.Checked)
            {
                wherelist.Add("mzh=@mzh");
                parametlist.Add(new SqlParameter("@mzh", TbMzh.Text));
            }
            if (CbXm.Checked)
            {
                wherelist.Add("xm like '%'+@xm+'%'");
                parametlist.Add(new SqlParameter("@xm", TbXm.Text));
            }
            if (CbJbmc.Checked)
            {
                wherelist.Add("jbzd like '%'+@jbzd+'%'");
                parametlist.Add(new SqlParameter("@jbzd", TbJbmc.Text));
            }
            if (CbJzlb.Checked)
            {
                wherelist.Add("jzlb=@jzlb");
                parametlist.Add(new SqlParameter("@jzlb", ComBoxJzlb.Text));
            }
            if (CbJzks.Checked)
            {
                wherelist.Add("jzks=@jzks");
                parametlist.Add(new SqlParameter("@jzks", TbJzks.Text));
            }
            if (CbJzys.Checked)
            {
                wherelist.Add("jzys=@jzys");
                parametlist.Add(new SqlParameter("@jzys", TbJzys.Text));
            }
            if (CbJzrq.Checked)
            {
                wherelist.Add("jzrq between @start and @end");
                string start = DpStart.Value.ToString("yyyy-MM-dd") + " 00:00:00";
                string end = DpEnd.Value.ToString("yyyy-MM-dd") + " 23:59:59";
                parametlist.Add(new SqlParameter("@start", start));
                parametlist.Add(new SqlParameter("@end", end));
            }
            if (CbJbmcjqcx.Checked)
            {
                wherelist.Add("jbzd = @jbzd");
                parametlist.Add(new SqlParameter("@jbzd", TbJbmc1.Text));
            }
            string whereSql = string.Join(" and ", wherelist);
            string sql = "select mzh,xm,xb,csny,age,pcid,jzks,jzys,jbzd,zddm,gzdw,jtzz,lxfs,jzlb,jzrq,xy from his_mzjzrz";
            if (wherelist.Count > 0)
            {
                sql = sql + " where " + whereSql + " order by jzrq desc";
            }
            else
            {
                MessageBox.Show("请选择检索条件！");
                return;
            }
            DataTable dt = MsSqlHelper.ExecuteDataTable(sql, parametlist.ToArray());
            MzrzGridView.DataSource = dt;
            toolStripStatusLabel2.Text = string.Format("共检索到{0}条记录", dt.Rows.Count.ToString());
            toolStripProgressBar1.Minimum = 0;
            toolStripProgressBar1.Maximum = dt.Rows.Count;
            for (int i = 0; i <= dt.Rows.Count; i++)
            {
                toolStripProgressBar1.Value = i;
            }

        }