linqor怎麼寫

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 大概是這樣，如果有bug 請你自己調下。

當然，可以自己手寫，但是大多數時候我們不會手寫。

手寫連線資料庫這塊，一般用於做個教程之類的，簡單直觀。

我也簡單的寫一個，以SQL SERVER的NORTHwinD資料庫為例吧：

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);

我還是貼程式碼吧，說是說不明白的。

以下是我的一個專案裡面的節選，分別實現了增刪查改功能，你可以看看LINQ對資料的操作。

/// <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;

}

DateTime dt = DateTime.Now； //當前時間

DateTime startWeek = dt.AddDays(1 - Convert.ToInt32(dt.DayOfWeek.ToString("d")））； //本週週一

DateTime endWeek = startWeek.AddDays(6)； //本週週日

var q = items.where(p=>p.date >= startWeek && p.date