CODEWITHSUNDEEP
c#linqgenerics
Mostafa Bouzari
Mostafa Bouzari

Reputation: 10230

Cannot implicitly convert type 'System.Collections.Generic.List<<anonymous type>>' to 'System.Collections.Generic.List<string>'

my code supposed to check two conditions and return the values but when i try to return q this error shows up

Cannot implicitly convert type 'System.Collections.Generic.List<< anonymous type: string Name, string File>>' to 'System.Collections.Generic.List< string>

and i tried everything but nothing worked also don't know to set List<string> or set it as List<EF_Model.PDF> ,PDF is a DTO in my model

this is my code 

  internal List<string> Customers_File(int _id)
    {
        using (var Context = new EF_Model.CoolerEntities())
        {
            var q = from c in Context.Customers
                    where c.Id == _id &&
                    c.Ref_PDF != null
                    select new { c.PDF.Name, c.PDF.File };
            return q.ToList();
        }
    }

Upvotes: 5

Views: 13063

Answers (4)

Jamiec
Jamiec

Reputation: 136074

You need to define an object with your to properties

public class PdfInfo
{
    public string Name{get;set;}
    public string File{get;set;}
}

Return a list of them from your method

internal List<PdfInfo> Customers_File(int _id)

And finally project to those, in place of an anonymous object:

....
select new PdfInfo() { Name=c.PDF.Name, File = c.PDF.File };

Upvotes: 1

steliosbl
steliosbl

Reputation: 8921

You are getting this error because you have defined Customers_File as returning a list of strings. However, the list q that you return doesn't fit that description.

In your query, when you do

select new { c.PDF.Name, c.PDF.File };

..you are making an Anonymous Type, and storing it in the collection q. This type has two fields and is clearly not a string.

Some possible solutions are:

  • Change your method to have return type List<object> instead of List<string> (not recommended).
  • Make your object into a string via some form of serialization (JSON or XML).
  • Create a class or struct for this data and change the return type of your method to List<dataClass>

Upvotes: 0

GraemeMiller
GraemeMiller

Reputation: 12253

You have declared your return type as string but are returning an a list of anonymous objects with two properties. That won't work. If you want to return a string you need to create a single string per list item. If you want to return object change your return type

Upvotes: 0

MistyK
MistyK

Reputation: 6222

You have to convert the anonymous object into a string representation.(Note I'm using C# 6.0 feature - string interpolation, you can replace it with string.Format in the previous versions. Example:

return q.Select(x=>$"Name = {x.PDF.Name} File = {c.PDF.File}").ToList();

Upvotes: 3

Related Questions