CODEWITHSUNDEEP
c#linqlist
Bob Tway
Bob Tway

Reputation: 9613

What return type to use for a method that returns a list of anonymous type?

Doing some refactoring of old code, the developer responsible long having left.

He bequeathed me this bit of Linq:

var orders = memberOrders
   .Join(members, x => x.MemberID, y => y.MemberID, (x,y) => new { Order = x , y.MemberName })
   .OrderByDescending(x => x.Order.MailingDate).ToList();

Which creates some sort of dual value list with an Order object connected to a MemberName string for that object.

I want a function to return this. However, I cannot figure out what type it is that the function needs to return.

Calling GetType() reveals it's called List`1, which isn't terribly helpful. It looks like a List<T> constructed on the fly by the compiler into a custom object.

What is it, and how can I return it from a function?

Upvotes: 1

Views: 118

Answers (3)

Christos
Christos

Reputation: 53958

It's a list of objects of an anonymous type with two properties.

The first property is called Order and the second is called MemberName.

I want a function to return this. However, I cannot figure out what type it is that the function needs to return.

It would be more meaningful then, if you could define a class with this two properties and then return a sequence of them. Like below:

public class ClassName
{
    public TypeOfOrder Order { get; set; }
    public TypeOfMemberName MemberName { get; set; }   
}

Then you declare the method for getting the orders. 

public IEnumerable<ClassName> GetOrders()
{
   var orders = memberOrders.Join(members, 
                                  x => x.MemberID, 
                                  y => y.MemberID, 
                                 (x,y) => new ClassName 
                                 { 
                                     Order = x,
                                     MemberName = y.MemberName 
                                 }).OrderByDescending(x => x.Order.MailingDate);           
    return orders;
}

Upvotes: 1

D Stanley
D Stanley

Reputation: 152644

It's returning an list of an anonymous type with two properties: Order and MemberName. Technically you can return a list of an anonymous type (the return type could be object or List<dynamic>), but you then require the caller to use reflection or dynamic to access the properties.

It's safer to create a new type (or use an existing one) and return a list of that instead.

Upvotes: 8

Adriano Carneiro
Adriano Carneiro

Reputation: 58665

It's a list of an anonymous type created at:

new { Order = x , y.MemberName }

Upvotes: 1

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