var result=from t in
(from p in A join q in B
on new {TId=p.id} equals new {TId=q.id}
into tempList
from tt in tempList.DefaultIfEmpty()
select new{aid=(tt == null ? 0 : tt.id),
name=(tt == null ? 0 : tt.name)})
group t by new {t.aid,t.name}
into g
select new{num=g.Count(t=>t.aid),aid=t.aid,name=t.name};
手打linq 大概是这样，如果有bug 请你自己调下。
2. LINQ 怎么写查询,自己写的当然，可以自己手写，但是大多数时候我们不会手写。
手写连接数据库这块，一般用于做个教程之类的，简单直观。
我也简单的写一个，以SQL SERVER的NORTHwinD数据库为例吧：
var db = new DataContext
(@"Data Source=(local);Initial Catalog=Northwind;Integrated Security=true;");
var results = from c in db.GetTable<Customer>()
where c.City == "London"
select c;
foreach (var c in results)
Console.WriteLine("{0}t{1}", c.CustomerID, c.City);
3. LinQ中增删改语句如何写我还是贴代码吧，说是说不明白的。
以下是我的一个项目里面的节选，分别实现了增删查改功能，你可以看看LINQ对数据的操作。
/// <summary>
/// Select
/// </summary>
/// <returns></returns>
public IQueryable Linqmy()
{
var my = from s in db.account select s;
return my;
}
/// <summary>
/// Insert
/// </summary>
/// <param name="name"></param>
/// <param name="pwd"></param>
/// <returns></returns>
public bool LinqInsertmy(string name,string pwd)
{
account account = new account();
account.name = name;
account.pwd = pwd;
db.account.InsertOnSubmit(account);
db.SubmitChanges();
return true;
}
/// <summary>
/// Delete
/// </summary>
/// <param name="id"></param>
/// <returns></returns>
public bool LinqDelete(int id)
{
account account = db.account.Single(a => a.id == id);
db.account.DeleteOnSubmit(account);
db.SubmitChanges();
return true;
}
/// <summary>
/// Update
/// </summary>
/// <param name="id"></param>
/// <param name="name"></param>
/// <param name="pwd"></param>
/// <returns></returns>
public bool LinqUpdate(int id, string name, string pwd)
{
account account = db.account.Single(a => a.id == id);
account.name = name;
account.pwd = pwd;
db.SubmitChanges();
return true;
}
4. linq 查询本周的所有信息DateTime dt = DateTime.Now； //当前时间
DateTime startWeek = dt.AddDays(1 - Convert.ToInt32(dt.DayOfWeek.ToString("d")））； //本周周一
DateTime endWeek = startWeek.AddDays(6)； //本周周日
var q = items.where(p=>p.date >= startWeek && p.date
