多条件查询access数据库 - .NET技术 / ASP.NET

页面有5个dropdownlist（ddl1,ddl2,ddl3,ddl4,ddl5）一个TextBox (txt1)
他们可以任意组合去查询数据库
如果其中的莫一个为控制则不参与查询条件中，
能给个代码最好，给个思路也非常的感谢！

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string sql=" select * from table where 1=1"

if(ddl1.selectValue!=""){
  sql+=" and ddl='"+ddl1.selectValue+"'"
}
if(ddl2.selectValue!=""){
  sql+=" and ddl='"+ddl2.selectValue+"'"
}

如此这般

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写个拼写sql语句的函数
C# code:

string sqlStr = "select * from table1 where 1=1 "
if (param1.trim() ！= "")
sqlStr += "and column1='" + param1.trim();
........



 

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StringBuilder sb = new StringBuilder();
  sb.Append("select a.kh,a.name,b.fkfs,b.skje,b.czje,b.idate,b.czy from hyxx a,hycz b");
  sb.Append(" where a.id=b.hyid ");
  sb.Append(" and (a.kh=@kh or @kh is null)");
  sb.Append(" and (Convert(char(10),b.idate,120) >= @start or @start is null) ");
  sb.Append(" and(Convert(char(10),b.idate,120) <= @endTime or @endTime is null)");
  SqlParameter[] para = new SqlParameter[]