//<查询>按钮

    void btn_select_Click(object sender, EventArgs e)

    {

        using (CarDataContext con = new CarDataContext())

        {

            //进行查询，将查询到的数据放入Queryable集合中

            IQueryable<Car> clist = con.Car.AsQueryable();

            //其特点是：读到词句代码时不会立即执行，而是在进行数据绑定时执行

            //优点：此期间可以进行添加查询条件，以减少数据库查询内容，来减少内存占用量

            //对每一个条件文本框进行判断，是否有限制条件

            string name = txt_name.Text.Trim();

            string brand = txt_brand.Text.Trim();

            string price = txt_price.Text.Trim();

            if (name.Length > )

            {

                //如果有限制条件则添加查询条件

                clist = clist.Where(r => r.Name.Contains(name.Trim()));

            }

            if (brand.Length > )

            {

                clist = clist.Where(r => r.Brand.Contains(brand.Trim()));

            }

            if (price.Length > )

            {

                string s = DropDownList1.SelectedValue;

                if (s == "=")

                    clist = clist.Where(r => r.Price == Convert.ToDecimal(price));

                if (s == ">=")

                    clist = clist.Where(r => r.Price >= Convert.ToDecimal(price));

                if (s == "<=")

                    clist = clist.Where(r => r.Price <= Convert.ToDecimal(price));

            }

            //绑定数据-此时Queryable进行数据库查询并绑定数据

            Repeater1.DataSource = clist;

            Repeater1.DataBind();

        }

void Button2_Click(object sender, EventArgs e)

    {

        //先按照查询条件，将所有的数据分别查询全部出来

        using(mydbDataContext con = new mydbDataContext())

        {

            var nameList = con.car.AsQueryable();

            var brandList = con.car.AsQueryable();

            var priceList = con.car.AsQueryable();

            string name = txt_name.Text.Trim();

            string brand = txt_brand.Text.Trim();

            string price = txt_price.Text.Trim();

            if (name.Length > )

            {

                nameList = nameList.Where(r => r.name.Contains(name));

            }

            if (brand.Length > )

            {

                brandList = brandList.Where(r => r.brand.Contains(brand));

            }

            if (price.Length > )

            {

                string aa = DropDownList1.SelectedValue;

                if (aa == "=")

                    priceList = priceList.Where(r => r.price == Convert.ToDecimal(price));

                if (aa == ">=")

                    priceList = priceList.Where(r => r.price >= Convert.ToDecimal(price));

                if (aa == "<=")

                    priceList = priceList.Where(r => r.price <= Convert.ToDecimal(price));

            }

            //取集合的交集

            var allList = nameList.Intersect(brandList).Intersect(priceList);

            Repeater1.DataSource = allList;

            Repeater1.DataBind();

        }

    }