在linq中对wp7中的三个表进行联接查询 [英] join queries in linq for three table in wp7

问题描述

我已经在
下创建了一个Web服务.

i had created one web service as under

public List<String> ge()
   {
      var r = from c in db.Favourite_tbls
                join o in db.Menu_tbls on c.fk_menu_id equals o.pk_menu_id
               select new
               {
                   o.menu_name
               };
      return r.ToList();

   }

但这会在return语句中给我错误....
我的退货类型应该是什么..

but it will give me error in return statement....
what should my return type..

Error:

cannot implicitly converts type system.collection.generic.list(annoymus type#1) to 
system.collection.generic.list(string)

推荐答案

问题实际上是Linq问题，而不是WP7问题.当您执行select new {...}语句时，该查询将成为匿名类型.这与List< string>方法的返回类型.

您也许可以尝试像这样更改查询...

The issue is really a Linq issue here and not a WP7 one. The query makes an anonymous type when you do the select new { ... } statement. This is not the same as the List<string> return type for the method.

You might be able to try changing the query like this...

public List<String> ge()
   {
      var r = from c in db.Favourite_tbls
                join o in db.Menu_tbls on c.fk_menu_id equals o.pk_menu_id
               select new String(o.menu_name);
      return r.ToList();

   }

您也可以创建一个仅包含字符串的类，并使用它.如果您想要其中的一个样本，请告诉我.

You could also make a class that just had a string in it and use that as well. If you want a sample of that let me know.

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