与WCF一起使用时如何在linq中给别名

本文介绍了与WCF一起使用时如何在linq中给别名的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

我在WCF上使用LINQ 在.dbml文件中，我拖动了sql表，在IService1.cs文件中，我的代码是:

I am using LINQ with WCF in the .dbml file I dragged the sql table, my code in IService1.cs file is:

[OperationContract] List<ASX_D> ASX_D12(String tablename, String company);

我在Service1.svc.cs中的代码是

and my code in Service1.svc.cs is

public List<ASX_D> ASX_D12(string tablename, string company) { var q = (from p in db.ASX_Ds where p.ASX_D_name == company select new { qq=p.ASX_D_close , ff=p.ASX_D_date, ss=p.ASX_D_exchange, oo=p.ASX_D_high, gg=p.ASX_D_low, fg=p.ASX_D_name, dfgdfg=p.ASX_D_open qweqwe=p.ASX_D_sector, cvbcvb=p.ASX_D_symbol, aedasew=p.ASX_D_time, sdfsdf=p.ASX_D_type,ruwoeru=p.ASX_D_volume }); return q.ToList();

但它给出了错误

but it give the error

Cannot implicitly convert type 'System.Collections.Generic.List<AnonymousType#2>' to 'System.Collections.Generic.List<SilverlightProjectwithWCF.Web.ASX_D>' C:\Documents and Settings\hgtech\Desktop\SilverlightProjectwithWCF\SilverlightProjectwithWCF.Web\Service1.svc.cs 134 20 SilverlightProjectwithWCF.Web

How we can give an alias to columns in a LINQ query?

推荐答案

此代码应该有效: This code should work: var q = (from p in db.ASX_Ds where p.ASX_D_name == company select p; return q.ToList();

不需要中间匿名类型，实际上不能将其强制转换为泛型中的返回类型，因此，您想要的类型别名对于像C#这样的强OO语言来说是不起眼的. 如果要限制字段，则应声明 DataContract [ ^ ]包含您要转换的字段，您可以编写转换方法并通话 q.ToList().ConvertAll<datacontracttype>(ConversionFunction); 请参阅列表< T>.方法 [ ^ ] 即使您要发送所有数据，这种转换也是值得的，因为它将接口与对象模型和数据库实现分离开来，并允许服务的版本控制.

The intermediate anonymous type is not required, in fact it can''t be cast to the return type in the generic, so the type aliasing you want is a non-starter in a strongly OO language like C#. If you want to restrict the fields you should declare a DataContract[^]with the fields you want and convert, you can write convertor method and an call q.ToList().ConvertAll<datacontracttype>(ConversionFunction); See List<T>.ConvertAll<TOutput> Method [^] Such conversion is worthwhile even if you want to send all the data as it de-couples your interface from your object model and database implementation and allows versioning of the service.