Return type from a Linq using a simple table

Question

Very simple basic thing...but it's driving me in nuts.To be direct: What's wrong ?

        public List<PAGE> ListAllPages(int PortalId, string KeyPar1, string KeyPar2, string Culture)
        {
            SqlServerDataContext SqlServer = new SqlServerDataContext();
            var AllPages = (from p in SqlServer.PAGEs
                            where p.Culture.Equals(Culture)
                            orderby p._DateTime descending
                            select new { p._DateTime, p.Title, p.Tag, p.Briefing  });
            return AllPages.ToList();
        }

The return line is the error:

Error 1 Cannot implicitly convert type 'System.Collections.Generic.List<AnonymousType#1>' to 'System.Collections.Generic.List<Newton.PAGE>' c:\users\marcojr\documents\visual studio 11\Projects\Newton\Newton\Newton.svc.cs 21 20 Newton

Answer 1

Hi MarcoJr;

In the function signature it states that you will be returning a List<PAGE> data type but what you are returning is a collection of Anonymous type. This part of the query :

select new { p._DateTime, p.Title, p.Tag, p.Briefing  });

Creates an Anonymous type that is returned in a collection.

It is not a good idea to return an Anonymous type from a function so you have a couple of options return a complete row of PAGEs which will correct the issue making the select clause as follows:

select p);

Or create a new class to hold a new type and return that to the caller of the function. So let say we create a new class called PartOfPage then you will need to change the select to this:

select new PartOfPage { DT = p._DateTime, Title = p.Title, Tag = p.Tag, Briefing = p.Briefing  });

// Correct the data type for the properties
public class PartOfPage
{
    public DateTime DT { get; set; }
    public String Title { get; set; }
    public String Tag { get; set; }
    public String Briefing { get; set; }
}

and change the return type of the function to List<PartOfPage>.

Hope that helps.

  

---

Fernando (MCSD)

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Answer 2

 public List<PAGE> ListAllPages(int PortalId, string KeyPar1, string KeyPar2, string Culture)
        {
            SqlServerDataContext SqlServer = new SqlServerDataContext();
            var AllPages = (from p in SqlServer.PAGEs
                            where p.Culture.Equals(Culture)
                            orderby p._DateTime descending
                            select new PAGE{_DateTime= p._DateTime, Title= p.Title, Tag=p.Tag, Briefing=p.Briefing  });
            return AllPages.ToList();
        }

    Hope it can give you some help.

---

Best Regards,
If a post answers your question, please click "Mark As Answer" on that post and "Mark as Helpful".

Answer 3

Nope..I performed this way in another method..check this..

        public List<CATEGORy> ListEnabledCategories(int PortalId, string KeyPar1, string KeyPar2, string Culture, int ParentId)
        {
            SqlServerDataContext SqlServer = new SqlServerDataContext();
            var Cats = (from p in SqlServer.CATEGORies
                        where p.PortalId.Equals(PortalId)
                        where p.Culture.Equals(Culture)
                        where p.IsActive.Equals(true)
                        where p.ParentId.Equals(ParentId)
                        orderby p._Order
                        select new CATEGORy {   Name = p.Name,
                                                CustomOptions=p.CustomOptions,
                                                Tag= p.Tag
                        });      
            return Cats.ToList();

        }

And the error is the same on this page :http://msdn.microsoft.com/query/dev11.query?appId=Dev11IDEF1&l=EN-US&k=k(EHNotSupported);k(TargetFrameworkMoniker-.NETFramework,Version%3Dv4.5);k(DevLang-csharp)&rd=true

Because Category is a table like Page is a table too.

 public List<PAGE> ListAllPages(int PortalId, string KeyPar1, string KeyPar2, string Culture)
        {
            SqlServerDataContext SqlServer = new SqlServerDataContext();
            var AllPages = (from p in SqlServer.PAGEs
                            where p.Culture.Equals(Culture)
                            orderby p._DateTime descending
                            select new PAGE{_DateTime= p._DateTime, Title= p.Title, Tag=p.Tag, Briefing=p.Briefing  });
            return AllPages.ToList();
        }

    Hope it can give you some help.

---

Best Regards,
If a post answers your question, please click "Mark As Answer" on that post and "Mark as Helpful".

Answer 4

Hi MarcoJr,

Does this issue has been resolved yet? If it doesn’t I would suggest you should get a try on Fernando’s advice or you could update the latest status of this issue here.

Best Regards,

---

Tony Xiao [MSFT]
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