InnerJoin操作：

 

private void InnerJoinQuery()

     {    ///构建数据源

         List<UserInfo> users = new List<UserInfo>();

         List<RoleInfo> roles = new List<RoleInfo>();

         for (int i = 1; i < 10; i++)

         {

              users.Add(new UserInfo(i, "User0" + i.ToString(),"User0" + i.ToString() + "@web.com",i * 2));

              roles.Add(new RoleInfo(i,"RoleName0" + i.ToString()));                               u.RoleID

         }

          ///查询ID值小于9，且角色包含在roles中的用户

        var value = from u in users

                    where u.ID < 9

                    join r in roles on u.RoleID equals r.ID   //找出u.RoleID与r.ID相同的u和r

                    select new

                    {

                        u.Username,

                        r.RoleName

                    };