For example, a single query can retrieve data from an SQL database and produce an XML stream as output. Query expressions use many familiar C# language constructs, which make them easy to read. The variables in a query expression are all strongly typed. A query isn't executed until you ...
Customers where (from o in db.Orders where o.ShipCountry == “Germany” select o.CustomerID).Contains(c.CustomerID); This query can't be handled by the current data layer, and while no errors are diagnosed at compile time, an error would occur at run time....
LINQDev.Common.Contact.PublishContacts(contacts); 转换Employee对象的ArrayList 为Contact对象数组,我首先将Employee对象的ArrayList使用Cast Standard Query Operator转换成一个IEnumerable<Employee>序列。这是必须的,因为要使用旧的ArrayList集合类。语法上说,ArrayList是存储System.Object 类 类型对象。所以我必须转换Employee...
System.Data.Linq.DataQuery`1[nwind.Order] 这里有一些编译器乱码,但是重要的是nwind.Order部分。 你现在知道如何获取一个nwind.Order序列的数据类型了吧。 如果在debugger下运行该例子时你将乱码throw出来,并检查orders变量,将会在本地窗体显示orders数据类型如下: System.Linq.IQueryable<nwind.Order>{System.Data.L...
When you write queries, the most visible "language-integrated" part of LINQ is the query expression. Query expressions are written in a declarativequery syntax. By using query syntax, you perform filtering, ordering, and grouping operations on data sources with a minimum of code. You use the ...
Northwnd db = new Northwnd(@"c:\northwnd.mdf"); // Query for customers in London. IQueryable<Customer> custQuery = from cust in db.Customers where cust.City == "London" select cust; For more information about how to create specific types of data sources, see the documentation for the ...
With LINQ, a query is a first-class language construct, just like classes, methods, and events. When you write queries, the most visible "language-integrated" part of LINQ is the query expression. Query expressions are written in a declarative query syntax. By using query syntax, you ...
Example - Query syntax Show 6 more Most queries in the introductory Language Integrated Query (LINQ) documentation are written by using the LINQ declarative query syntax. The C# compiler translates query syntax into method calls. These method calls implement the standard query operators, and have na...
// var is used for convenience in these queriesdoubleaverage = numbers1.Average();varconcatenationQuery = numbers1.Concat(numbers2);varlargeNumbersQuery = numbers2.Where(c => c >15); 示例- 混合查询和方法语法 此示例演示如何对查询子句的结果使用方法语法。 只需将查询表达式括在括号中,然后应用点...
from num in numbers where (num % 2) == 0 select num; // 3. Query execution. foreach (int num in numQuery) { Console.Write("{0,1} ", num); } } } 下图演示完整的查询操作。 在 LINQ 中,查询的执行不同于查询本身。 换句话说,仅通过创建查询变量不会检索到任何数据。