模型和部分模型，如何避免冗余代码？

Question

I have a model and a partial model which contains only the properties that I need to expose in JSON.

But the properties between the model and his partial model are redundant.

How can I avoid that or improve my approach?

namespace Dashboard.Models.UserModels
{
    public class UserModel
    {
        public int id { get; set; }
        public string dbName { get; set; }
        public string firstname { get; set; }
        public string lastname { get; set; }
        public int idExternal { get; set; }
        public int idInstance { get; set; }
        public string login { get; set; }
        public string password { get; set; }
        public DateTime? dtContractStart { get; set; }
        public DateTime? dtContractEnd { get; set; }
        public string emailPro { get; set; }
        public string emailPerso { get; set; }

        public LuccaUserModel()
        {
            idInstance = -1;
        }

        // partial model for json result
        // not sure is the best way or have to be here
        public class PartialUserModel
        {
            public int id { get; set; }
            public string firstname { get; set; }
            public string lastname { get; set; }
            public string emailPro { get; set; }
            public string emailPerso { get; set; }
            public DateTime? dtContractStart { get; set; }
            public DateTime? dtContractEnd { get; set; }
            public string url { get; set; }
        }

        // UserModel Methods
    }
}

Answer 1

You can rename PartialUserModel UserModelBase class (or leave it as is... it just makes better logical sense to do so) and make UserModel to inherit from it:

public class UserModel : UserModelBase
{
    ...
}

Of course you'll need to remove all duplicate properties from UserModel in this case.

Answer 2

It's a thin line between doing a proper design and building an overkill design. Answer depends on many inputs, among which I chose to have project and model breadth most important.

In hope to have my answer clearer, I have to say I use different terminology. Data which is adopted for use in UI is usually called ViewModel. In your case, you would build UserViewModel which contains necessary subset of information.

If I'm working on a one-off project, I'll reuse model as a ViewModel. I'll do this by having helper method which removes sensitive information, loads up or cuts off data which is lazy loaded from database and does other preparation on data. All this is done with same model class.

If it's not a short term project, I look to create separate ViewModel classes which I map from model data. Then, if I'm working with mostly flat data I use AutoMapper tool to have data automatically copied, instead of writing my own mappers.

As another answer here states, you write a basic class with data you need in UI and extend it with other model data, however this is not a good approach for several reasons.

1. If violates separation of concerns. Project dealing with model and persistance should not know about your ViewModel
2. You may need to flatten data from related objects into ViewModel objects. In that case, your model objects would have fields which should not be there, or would be redundant.
3. You may need calculated fields and helper methods in ViewModel which would again end up in model, confusing everyone that is not updated about design.
4. You could want to adopt several unrelated model classes to same ViewModel class

To try and put it shortly, either reuse model class or create ViewModels. There is unfortunately no clever solution. If you find one, please post a comment as I'd like to hear about it :)