无法将dto列表转换为动态列表

Question

How can I make this to work? It giving me an error cannot implicitly convert . I have lots of DTO on my WebApp and I need a placeholder variable.

NOTE: This is not the actual code on my WebApp, this is just the same idea on what I want to do.

public class DTO1
{
    public int Id { get; set; }
    public string Name { get; set; }
}

public class DTO2
{
    public int Id { get; set; }
    public string Name { get; set; }
}

public class DTO1Service
{
    public static List<DTO1> GetListOfDTO1()
    {
        return new List<DTO1>
        {
            new DTO1 { Id = 1, Name = "DTO 1" },
            new DTO1 { Id = 2, Name = "DTO 2" }
        };
    }
}

public class DTO2Service
{
    public static List<DTO2> GetListOfDTO2()
    {
        return new List<DTO2>
        {
            new DTO2 { Id = 1, Name = "DTO 1" },
            new DTO2 { Id = 2, Name = "DTO 2" }
        };
    }
}

public class Program
{
    public static void Main(string[] args)
    {
        var entities = new List<dynamic>();

        var serviceType = Console.ReadLine();

        if(serviceType == "1")
            entities = (dynamic)DTO1Service.GetListOfDTO1();
        else if (serviceType == "2")
            entities = (dynamic)DTO2Service.GetListOfDTO2();

        Console.ReadLine();
    }
}

Answer 1

You can use Cast method to explicitly cast it to dynamic , like so:

if(serviceType == "1")
        entities = DTO1Service.GetListOfDTO1().Cast<dynamic>().ToList();
else if (serviceType == "2")
        entities = DTO2Service.GetListOfDTO2().Cast<dynamic>().ToList();

Answer 2

You are casting it wrong. You are trying to assign a dynamic to a List<dynamic> instead of the list members

You can either create a new instance and pass the values in

if(serviceType == "1")
    entities = new List<dynamic>(DTO1Service.GetListOfDTO1());
else if (serviceType == "2")
    entities = new List<dynamic>(DTO2Service.GetListOfDTO2());

or just populate the initially created instance

if(serviceType == "1")
    entities.AddRange(DTO1Service.GetListOfDTO1());
else if (serviceType == "2")
    entities.AddRange(DTO2Service.GetListOfDTO2());

I personally prefer the second option as you have already initialized the variable and would just be populating it instead of creating an instance just to reassign it after.

Answer 3

Based on the comment on the question, I am under the impression that OP needed something like that:

public interface IAmDTO {

    int Id { get; set; }

    string Name { get; set; }
}

public class DTO1 : IAmDTO {

    public int Id { get; set; }

    public string Name { get; set; }
}

public class DTO2 : IAmDTO {

    public int Id { get; set; }

    public string Name { get; set; }
}

public class DTO1Service {

    public static List<DTO1> GetListOfDTO1() =>
        new List<DTO1>
        {
        new DTO1 { Id = 1, Name = "DTO 1" },
        new DTO1 { Id = 2, Name = "DTO 2" },
        };
}

public class DTO2Service {

    public static List<DTO2> GetListOfDTO2() =>
        new List<DTO2>
        {
        new DTO2 { Id = 1, Name = "DTO 1" },
        new DTO2 { Id = 2, Name = "DTO 2" },
        };
}
}

public static class DTOExtensions {

public static void DtoHelper(this IEnumerable<IAmDTO> dtoS) {
    foreach(var dto in dtoS) {
        //DO SOMETHING WITH
        var id = dto.Id;
        var name = dto.Name;
    }

}

}