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

/// 
        /// 按条件查询        /// 
        ///         ///         private void BtSearch_Click_1(object sender, EventArgs e)        {            List
     
       wherelist = new List
      
       ();            List
       
         parametlist = new List
        
         ();                        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;            }        }