Question

fromI have this linq query to build a json (of string and bool?) from an IQueryable :

var ret = from c in results select new { country = c.EN, schengen = c.Schengen };

I would like to append new items to it manually : (pseudo code)

ret = ret /* add this -> */ { country = "some new country", schengen = true }

I’ve tried to do that :

//End up with cannot convert from AnonymousType#2 to AnonymousType#1
var listRet = ret.ToList();
listRet.Add(new { country ="", schengen = true });

As it is an anonymous type that I build I cannot find a way to add it. I always end up with conversion error

Answer 1

Anonymous types are still statically typed and C# compiler generates a separate class for each anonymous type definition occurrence. You need a named class in this case. It’s a good practice for data transfer objects anyway. I use JSON DTOs like this, using data annotations and DataContractJsonSerializer.

[DataContract]
public class CountryInfo
{
    [DataMember(Name = "country")]
    public string Country { get; set; }

    [DataMember(Name = "schengen", EmitDefaultValue = false)
    public bool? Schengen { get; set; }
}

This way I have a well-documented JSON “protocol”, which also uses C# naming conventions before serialization, but JS naming conventions after.