Linq To Entities 的語(yǔ)法基礎(chǔ)可以參考：

Microsoft Language Integrated Query (LINQ) 從入門到精通

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1.使用ObjectQuery類的ToTraceString()方法顯示查詢SQL語(yǔ)句

???????????? Console.WriteLine(customers.ToTraceString());

2.基于表達(dá)式的查詢語(yǔ)法

??? ObjectQuery<Customers> customers = edm.Customers;

??? IQueryable<Customers> cust1 = from c in customers

????????????????????????????????? where c.CustomerID == "ALFKI"

????????????????????????????????? select c;

3.基于方法的查詢語(yǔ)法

??? var cust2 = edm.Customers.Where(c => c.CustomerID == "ALFKI");

4.排序分頁(yè)

IQueryable<Customers> cust10 = (from c in customers

??????????????????????????????????????? orderby c.CustomerID

??????????????????????????????????????? select c).Skip(0).Take(10);

或者

var cust = edm.Customers.OrderBy(c => c.CustomerID).Skip(0).Take(10);

5.可使用的聚合運(yùn)算符有Average、Count、Max、Min 和 Sum。

????? var maxuprice = edm.Products.Max(p => p.UnitPrice);

????? Console.WriteLine(maxuprice.Value);

6. 可以的連接有Join 和 GroupJoin 方法。GroupJoin組聯(lián)接等效于左外部聯(lián)接，它返回第一個(gè)（左側(cè)）數(shù)據(jù)源的每個(gè)元素（即使其他數(shù)據(jù)源中沒(méi)有關(guān)聯(lián)元素）。

using (var edm = new NorthwindEntities())

??? {

????? var query = from d in edm.Order_Details

????????????????? join order in edm.Orders

????????????????? on d.OrderID equals order.OrderID

????????????????? select new

??????????????????? {

??????????????????????? OrderId = order.OrderID,

??????????????????????? ProductId = d.ProductID,

??????????????????????? UnitPrice = d.UnitPrice

??????????????????? };

??????? foreach (var q in query)

??????? Console.WriteLine("{0},{1},{2}",q.OrderId,q.ProductId,q.UnitPrice);

}

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參考文章：

http://www.pin5i.com/showtopic-24045.html

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未完成！

轉(zhuǎn)載于:https://www.cnblogs.com/doubleyan/archive/2010/03/07/2164770.html

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