c# - Enum description to string with AutoMapper

Question

I'm trying to project from my Order model to my OrderDTO model. Order has an enum. The problem is that projection doesn't work if I try to to get the Description attribute from the Enum. Here it's my code:

• OrderStatus.cs:

  public enum OrderStatus {
      [Description("Paid")]
      Paid,
  
      [Description("Processing")]
      InProcess,
  
      [Description("Delivered")]
      Sent
  }
  

• Order.cs:

  public class Order {
      public int Id { get; set; }
      public List<OrderLine> OrderLines { get; set; }
      public OrderStatus Status { get; set; }
  }
  

• OrderDTO.cs:

  public class OrderDTO {
      public int Id { get; set; }
      public List<OrderLineDTO> OrderLines { get; set; }
      public string Status { get; set; }  
  }
  

With this following configuration in my AutoMapper.cs:

cfg.CreateMap<Order, OrderDTO>().ForMember(
    dest => dest.Status,
    opt => opt.MapFrom(src => src.Status.ToString())
);

Projection works, but I get an OrderDTO object like this:

 - Id: 1
 - OrderLines: List<OrderLines>
 - Sent //I want "Delivered"!

I don't want Status property to be "Sent", I want it to be as its associated Description attribute, in this case, "Delivered".

I have tried two solutions and none of them have worked:

1. Using ResolveUsing AutoMapper function as explained here, but, as it's stated here:

ResolveUsing is not supported for projections, see the wiki on LINQ projections for supported operations.

2. Using a static method to return the Description attribute in String by Reflection.

   cfg.CreateMap<Order, OrderDTO>().ForMember(
       dest => dest.Status,
       opt => opt.MapFrom(src => EnumHelper<OrderStatus>.GetEnumDescription(src.Status.ToString()))
   );
   

But this gives me the following error:

LINQ to Entities does not recognize the method 'System.String GetEnumDescription(System.String)' method, and this method cannot be translated into a store expression.

Then, how can I achieve this?

Answer 1

You can add an extension method like this one (borrowed the logic from this post):

public static class ExtensionMethods
{
    static public string GetDescription(this OrderStatus This)
    {
        var type = typeof(OrderStatus);
        var memInfo = type.GetMember(This.ToString());
        var attributes = memInfo[0].GetCustomAttributes(typeof(DescriptionAttribute), false);
        return ((DescriptionAttribute)attributes[0]).Description;
    }
}

Then access it in your map:

cfg => 
{
    cfg.CreateMap<Order, OrderDTO>()
    .ForMember
    (
        dest => dest.Status,
        opt => opt.MapFrom
        (
            src => src.Status.GetDescription()
        )
    );
}

This results in what you are asking for:

Console.WriteLine(dto.Status);  //"Delivered", not "sent"

See a working example on DotNetFiddle

Edit1: Don’t think you can add a local look up function like that to LINQ to entities. It would only work in LINQ to objects. The solution you should pursue perhaps is a domain table in the database that allows you to join to it and return the column that you want so that you don’t have to do anything with AutoMapper.