1、linq to sql 的多條件動態查詢確實是一件頭痛的事情，用表達式樹或反射方法要寫一大堆代碼，有時候想想與其這么復雜，還不如回到手動sql 拼接的年代，但是技術總是向前發展的，終歸還是要在linq 上解決這一問題，無意在網上發現一個還算比較簡單的辦法，分享一下: void showdata() using (dbdatacontext db = new dbdatacontext(database.connectionstring) expressionfunc expr = n = getcondition(n); var _query = db.t_bargins.where(expr

2、.compile().select(b = new b.f_money, b.f_name ); foreach (var item in _query) response.write(item.f_name +   + item.f_money.tostring() + ); / 得到合同金額大于6000, 或合同名稱中包含江華 字的條件private bool getcondition(t_bargin _table) bool _result = false ; decimal _minmoney = 6000 ; if (_minmoney 0) _result |=

3、 _table.f_money = _minmoney; string _name = 江華 ; if (!string.isnullorempty(_name) _result |= _table.f_name.contains(_name); return _result; 借助老外寫的一個擴展表達式的類，可以把上篇中的代碼寫得更優雅這是 predicatebuilder的源文件public static class predicatebuilder public static expressionfunc true () return f = true ; public static e

4、xpressionfunc false () return f = false; publicstatic expressionfunc or (this expressionfunc expr1, expressionfunc expr2) var invokedexpr = expression.invoke (expr2, expr1.parameters.cast (); return expression.lambdafunc (expression.or (expr1.body, invokedexpr), expr1.parameters); publicstatic expre

5、ssionfunc and (this expressionfunc expr1, expressionfunc expr2) var invokedexpr = expression.invoke (expr2, expr1.parameters.cast (); return expression.lambdafunc (expression.and (expr1.body, invokedexpr), expr1.parameters); 下面是使用示例：list getproductsbyand(params string keywords) dbdatacontext db = ne

6、w dbdatacontext(database.connectionstring); iqueryable query = db.products; foreach (string keyword in keywords) string temp = keyword; query = query.where(p = p.description.contains(keyword); / 翻譯后的sql 語句 : /select t0.id, t0.name, t0.description /from dbo.product as t0 /where (t0.description like %

7、手機 %) and (t0.description like %6111%) return query.tolist(); list getproductsbyor(params string keywords) dbdatacontext db = new dbdatacontext(database.connectionstring); var predicate = predicatebuilder.false(); foreach (string keyword in keywords) string temp = keyword; predicate = predicate.or(p

8、 = p.description.contains(temp); var query = db.products.where(predicate); / 翻譯后的sql 語句 : /select t0.id, t0.name, t0.description /from dbo.product as t0 /where (t0.description like %6111%) or (t0.description like %2350%) return query.tolist(); void showdata() /var _products = getproductsbyor(6111, 2

9、350); /repeater1.datasource = _products; /repeater1.databind(); var predicate = predicatebuilder.true(); string _name = 6111; if (! string .isnullorempty(_name) predicate = predicate.and(p = p.name.contains(_name); string _description = 長虹 ; if (! string .isnullorempty(_description) predicate = predicate.and(p = p.description.contains(_description); using (dbdatacontext db =