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最新推荐文章于 2025-09-10 21:59:39 发布

转载最新推荐文章于 2025-09-10 21:59:39 发布 · 69 阅读

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原文链接：http://www.cnblogs.com/pieux/archive/2012/04/29/2475915.html

文章标签：

#runtime #数据库

本文介绍了Simple.Data中动态查询的方法，包括使用Find和FindAllBy系列函数进行数据检索。通过这些函数可以灵活地构建复杂的查询条件，并支持LINQ风格的表达式。此外，还展示了如何利用这些方法执行更高级的操作，例如联表查询。

Simple.Data wiki 阅读 2

Finding data

Dynamic Find methods

The dynamic Table properties exposed by the Database object will accept a variety of methods starting with Find.

FindBy[…] returns a single dynamic object
FindAllBy[…] return an IEnumerable<dynamic>.

You can access the dynamic and get resolution at runtime or you can “project” to types you specify:

User u = (User)db.Users.FindById(23);
IEnumerable<User> u = db.Users.FindAllByName("Bob").Cast<User>();
IList<User> u = db.Users.All().ToList<User>();

简单翻译：动态Find方法，动态的表格属性接受一系列以Find开头的方法。返回的也是动态类型，所以要转换类型。

FindBy

Simple.Data:

db.Users.FindByNameAndPassword(name, password)

SQL:

SELECT * FROM Users WHERE Name = @p1 and Password = @p2

FindAllBy

Simple.Data:

db.Users.FindAllByType(“Admin”)

SQL:

 SELECT * FROM [Users] WHERE [Users].[Type] = @p1

FindAllBy with a list

Simple.Data:

db.Users.FindAllByType(new[] {"Admin",“Owner”,"CoAdmin"})

参数是一个匿名类，是一个字符串数组列表

SQL:

 SELECT * FROM [Users] WHERE [Users].[Type] IN (p1,p2,@p3)

FindAllBy with a Range

Simple.Data:

db.Users.FindAllByJoinDate(“2010-01-01”.to(“2010-12-31”))

SQL:

 SELECT * FROM [Users] WHERE [Users].[JoinDate] BETWEEN @p1 AND @p2

Find and FindAll

More complex criteria can be expressed using the Find and FindAll methods, which accept an expression, kind of similar to LINQ. Except not LINQ.

Simple.Data:

db.Users.Find(db.Users.JoinDate <= “2010-01-01”)

SQL:

SELECT * FROM [Users] WHERE [Users].[JoinDate] <= @p1

Criteria can be combined using the && and || operators. Parentheses for altering grouping of expressions are supported:

Simple.Data:

db.Users.Find(db.Users.Active.Like(“Y”) && db.Users.JoinDate <= “2010-01-01”)

SQL:

SELECT * FROM [Users] WHERE ([Users].[Active] LIKE @p1 AND [Users].[JoinDate]) <= @p2

Supported operators for Find

Joins

If you have referential integrity set up, Simple.Data will automatically apply joins for Find operations which use sub-object style criteria. Like this:

Simple.Data:

db.Customers.Find(db.Customers.Invoices.Paid == “N”)

SQL:

SELECT [Customers].* FROM [Customers] 
JOIN [Invoices] ON [Customers].[CustomerId] = [Invoices].[CustomerId] 
WHERE [Invoices].[Paid] = @p1

Getting all the data

You can use the All method to return all the data from a table:

Simple.Data:

db.Users.All()

SQL:

SELECT * FROM Users

Like FindAllBy it returns an IEnumerable<dynamic>.

posted on 2012-04-29 08:54 pieux 阅读( ...) 评论( ...) 编辑收藏

转载于:https://www.cnblogs.com/pieux/archive/2012/04/29/2475915.html