Linq基础 一、关键词： 1、form xx in xxx select => xx
static void Main(string[] args)
{
using (Model1 db = new Model1()) {
var qu = from s in db.TBLogins
select s;
foreach (var item in qu)
{
Console.WriteLine(item.MobileNumber);
}
}
}
where 筛选
static void Main(string[] args)
{
using (Model1 db = new Model1()) {
var qu = from s in db.TBUsers
where s.Avatar!=null
select s;
foreach (var item in qu)
{
Console.WriteLine(item.Avatar);
}
}
}
group...into:分组
static void Main(string[] args)
{
using (Model1 db = new Model1()) {
var qu = from s in db.TBUsers
group s by s.Sex
into g
select g;
foreach (var item in qu)
{
Console.WriteLine(item.Key);
Console.WriteLine(item.Count());
}
}
Console.ReadKey();
}
orderby...ascending(升序),descending（降序） 排序
static void Main(string[] args)
{
using (Model1 db = new Model1()) {
var qu = from s in db.TBUsers
group s by s.Sex
into g
orderby g.Key descending
select g;
foreach (var item in qu)
{
Console.WriteLine(item.Key);
Console.WriteLine(item.Count());
}
}
Console.ReadKey();
}
join...on..equal :表的关联
static void Main(string[] args)
{
using (Model1 db = new Model1()) {
var qu = from s in db.TBUsers
join a in db.TBLogins
on s.Id equals a.Id
select new { s, a };
foreach (var item in qu)
{
Console.WriteLine(item.a.MobileNumber);
Console.WriteLine(item.s.NickName);
}
}
Console.ReadKey();
}
let:临时变量
static void Main(string[] args)
{
using (Model1 db = new Model1()) {
var qu = from s in db.TBUsers
let a = s.NickName.Length
select new { a1 = a, s };
foreach (var item in qu)
{
Console.WriteLine(item.a1);
}
}
Console.ReadKey();
}
