ASP.NET EF 使用LinqPad 快速學習Linq

使用LinqPad這個工具可以很快學習並掌握linq[Language Integrated Query]

linqPad官方下載地址：http://www.linqpad.net/

linqPad4百度雲下載(for .NET Framework4.0/4.5)：鏈接：http://pan.baidu.com/s/1gflmRDp  密碼：3n3f

linqPad5百度雲下載(for .NET Framework 4.6)：鏈接：http://pan.baidu.com/s/1dE5Z0VB  密碼：qpgc

LINQPad is not just for LINQ queries, but any C#/F#/VB expression, statement block or program. Put an end to those hundreds of Visual Studio Console projects cluttering your source folder and join the revolution of LINQPad scripters and incremental developers.

Reference your own assemblies and NuGet packages. Prototype your ideas in LINQPad and then paste working code into Visual Studio. Or call your scripts directly from the command-line.

Experience LINQPad’s rich output formatting, optional debugger and autocompletion, and the magic of dynamic development and instant feedback! 

LINQPad 並非只為 LINQ 查詢，但任何 C# /F #/VB 表達式、 語句塊或程序。結束這些數百個視覺工作室控制台項目塞滿您的源文件夾和參加革命的 LINQPad 腳本編寫者和增量的開發人員。

引用你自己的程序集和 NuGet 程序包。原型的你的想法在 LINQPad，然后粘貼工作代碼到 Visual Studio。或直接從命令行調用您的腳本。

體驗 LINQPad 的豐富的輸出格式、 可選的調試器和自動完成和神奇的動態發展和即時反饋 ！

 

 

 先在數據庫創建一個數據庫MyFirstEF 和CustomerInfo和OrderInfo兩張表

create database MyFirstEF
on primary
(
    name='MyFirstEF.mdf',
    --修改為自己電腦上SQL DB路徑
    filename='E:\ProgramMSSQLServerDB\MyFirstEF.mdf',
    size=5mb,
    maxsize=100mb,
    filegrowth=10%
)
log on
(
    name='MyFirstEF_log.ldf',
    --修改為自己電腦上SQL DB路徑
    filename='E:\ProgramMSSQLServerDB\MyFirstEF_log.ldf',
    size=2mb,
    maxsize=100mb,
    filegrowth=5mb
)
go

use MyFirstEF
go

create table CustomerInfo
(
    id int identity(1,1) primary key,
    customerName nvarchar(100) not null,
    customerDate datetime
)
go

create table OrderInfo
(
  id int identity(1,1) primary key,
  orderName nvarchar(100),
  customerId int
)
go


insert into CustomerInfo 
select 'aa',GETDATE() union all
select 'bb',GETDATE() union all
select 'cc',GETDATE() union all
select 'dd',GETDATE() 
go

insert into OrderInfo
select 'bike1',2 union all
select 'bike2',2 union all
select 'car1',3 union all
select 'car2',3 union all
select 'chezi1',4 union all
select 'chezi2',4 union all
select 'test1',5 union all
select 'test2',5
go

select * from CustomerInfo
go

select * from OrderInfo
go

安裝完畢linqPad之后，打開軟件 --Add Connection-->Build data context automatically(Default(LINQ to SQL))

我們在linqPad的query標簽里把Language 選擇為c# Expression ，把Connection 選擇數據MyFirstEF 

1：Linq left join(left join 是Left outer join 簡寫)

在面板中輸入Linq，點擊運行或者直接按F5【注意CustomerInfo/OrderInfo及字段 都需要按照EF中的格式寫(不能按照數據庫格式)】

from c in CustomerInfo
join o in OrderInfo
on c.Id equals o.CustomerId
into MyLeftJoin
from tt in MyLeftJoin.DefaultIfEmpty()
select new 
{
    cname=c.CustomerName,
    //這里主要第二個集合有可能為空。需要判斷
    //oname=tt==null?"":tt.OrderName
    oname=tt.OrderName
}

對應SQL為：

SELECT [t0].[customerName] AS [cname], [t1].[orderName] AS [oname]
FROM [CustomerInfo] AS [t0]
LEFT OUTER JOIN [OrderInfo] AS [t1] ON ([t0].[id]) = [t1].[customerId]

對應lambda表達式為：

CustomerInfo
   .GroupJoin (
      OrderInfo, 
      c => (Int32?)(c.Id), 
      o => o.CustomerId, 
      (c, MyLeftJoin) => 
         new  
         {
            c = c, 
            MyLeftJoin = MyLeftJoin
         }
   )
   .SelectMany (
      temp0 => temp0.MyLeftJoin.DefaultIfEmpty (), 
      (temp0, tt) => 
         new  
         {
            cname = temp0.c.CustomerName, 
            oname = tt.OrderName
         }
   )

2:Linq right join(right join 是Right outer join 簡寫)[最后生成SQL還是left join]

 在面板中輸入Linq，點擊運行或者直接按F5

from o in OrderInfo
join c in CustomerInfo
on o.CustomerId equals c.Id
into MyRightJoin
from tt in MyRightJoin.DefaultIfEmpty()
select new
{
    //這里集合有可能為空。需要判斷
       //cname=tt==null?"":tt.CustomerName,
    cname=tt.CustomerName,
    oname=o.OrderName
}

對應SQL為：

SELECT [t1].[customerName] AS [cname], [t0].[orderName] AS [oname]
FROM [OrderInfo] AS [t0]
LEFT OUTER JOIN [CustomerInfo] AS [t1] ON [t0].[customerId] = ([t1].[id])

對應lambda表達式為：

OrderInfo
   .GroupJoin (
      CustomerInfo, 
      o => o.CustomerId, 
      c => (Int32?)(c.Id), 
      (o, MyRightJoin) => 
         new  
         {
            o = o, 
            MyRightJoin = MyRightJoin
         }
   )
   .SelectMany (
      temp0 => temp0.MyRightJoin.DefaultIfEmpty (), 
      (temp0, tt) => 
         new  
         {
            cname = tt.CustomerName, 
            oname = temp0.o.OrderName
         }
   )

3：Linq inner join

在面板中輸入Linq，點擊運行或者直接按F5

from c in CustomerInfo
join o in OrderInfo
on c.Id equals o.CustomerId
select new
{
    cname=c.CustomerName,
    oname=o.OrderName
}

對應SQL為：

SELECT [t0].[customerName] AS [cname], [t1].[orderName] AS [oname]
FROM [CustomerInfo] AS [t0]
INNER JOIN [OrderInfo] AS [t1] ON ([t0].[id]) = [t1].[customerId]

對應lambda表達式為：

CustomerInfo
   .Join (
      OrderInfo, 
      c => (Int32?)(c.Id), 
      o => o.CustomerId, 
      (c, o) => 
         new  
         {
            cname = c.CustomerName, 
            oname = o.OrderName
         }
   )

暫時就到這里，其他的參考官方文檔。 

 參考鏈接：

ASP.NET MVC EF直接更新數據(不需查詢)：http://www.cnblogs.com/Dr-Hao/p/5255630.html

ASP.NET EF(LINQ/Lambda查詢)：http://www.cnblogs.com/Dr-Hao/p/5356928.html