LINQ查询

一、条件查询

1.||查询

        //方式一
        var list = from message in sel.one where message.id == "1" || message.score == "60" select message;
        //方式二
        var list = sel.one.Where(r=>r.id=="1"||r.score=="60");

2.&&查询

        //方式一
        var list = from message in sel.one where message.id == "1" && message.score == "50" select message;
        //方式二
        var list = sel.one.Where(r => r.id == "1" && r.score == "60");

二、模糊查询

1.包含（任意位置）

        //方式一
        var list = from message in sel.one where message.score.Contains("5") select message;
        //方式二
        var list = sel.one.Where(r => r.score.Contains("5"));

2.开头

        //方式一
        var list = from message in sel.one where message.score.StartsWith("5") select message;
        //方式二
        var list = sel.one.Where(r => r.score.StartsWith("5"));

3.结尾

        //方式一
        var list = from message in sel.one where message.score.EndsWith("5") select message;
        //方式二
        var list = sel.one.Where(r => r.score.EndsWith("5"));

三、统计查询

1.个数

var count = con.car.Count();

2.最大值

var Max = con.car.Max(r => r.price);

3.最小值

var Min = con.car.Min(r => r.price);

4.平均值

var avg = con.car.Average(r => r.price);

四、分页查询

    int count = 5;//每页显示的条数
    int page = 1;//页码
    var list = sel.one.Skip(page*count).Take(count);//绑定数据

五、排序查询

1.升序

        //方式一
        var list = from message in sel.one orderby message.score ascending select message;//orderby 子句默认是升序
        //方式二
        var list = sel.one.OrderBy(r=>r.score);

2.降序

        //方式一
        var list = from message in sel.one orderby message.score descending select message;
        //方式二
        var list = sel.one.OrderByDescending(r => r.score);

六、外键显示

return this.brand1.brand_name;

七、组合查询

var list = list1.Intersect(list2).Intersect(list3);//符合list1和list2还有list3的三种查询条件的查询