I'm having serious doubts about the design for my Web application.

I wanted to separate the business logic from the interface so I made a Web API that handles all the requests to the database.

It's an ASP.NET Web API with Entity framework and a unit of work and generic repository pattern. So far, everything is good.

PROBLEM

Where I need help is I can't figure out an efficient way of sharing objects between the API and the application.

I don't want to serialize directly the entity object, I thought it would be a bad practice because if the entity model changes, I could end up with serializing large objects for no reason.

How it's implemented now

Because my interface is ASP.NET Web application in C# and my API is in C#, I made a common library with the definition of all my classes I want to share between them.

I know that solution won't work when I will develop an android app, I will have to create my classes again in Java but that's not my biggest problem.

The problem is I feel like I'm always converting my objects.

EXAMPLE

Here's an example of my work flow :

I start with a model with all the objects and the data annotations for my form then user would POST that model to a controller.

In the controller I have to convert this model to a class in my common library then send that object to my API.

Then a controller in my API catch the call and convert that object to an entity object to update the database.

So I have 3 classes

1. The model for the view with all the data annotation for the validation (Client)
2. The common library classes to share the objects (DLL)
3. The Entity classes (API)

I have a feeling that I do something really wrong. Is there something more elegant? I would like to make sure that I have a good solution for this problem before the project gets too big.

Thank you

I'm having serious doubts about the design for my Web application.

I wanted to separate the business logic from the interface so I made a Web API that handles all the requests to the database.

It's an ASP.NET Web API with Entity framework and a unit of work and generic repository pattern. So far, everything is good.

PROBLEM

Where I need help is I can't figure out an efficient way of sharing objects between the API and the application.

I don't want to serialize directly the entity object, I thought it would be a bad practice because if the entity model changes, I could end up with serializing large objects for no reason.

How it's implemented now

Because my interface is ASP.NET Web application in C# and my API is in C#, I made a common library with the definition of all my classes I want to share between them.

I know that solution won't work when I will develop an android app, I will have to create my classes again in Java but that's not my biggest problem.

The problem is I feel like I'm always converting my objects.

EXAMPLE

Here's an example of my work flow :

I start with a model with all the objects and the data annotations for my form then user would POST that model to a controller.

In the controller I have to convert this model to a class in my common library then send that object to my API.

Then a controller in my API catch the call and convert that object to an entity object to update the database.

So I have 3 classes

1. The model for the view with all the data annotation for the validation (Client)
2. The common library classes to share the objects (DLL)
3. The Entity classes (API)

I have a feeling that I do something really wrong. Is there something more elegant? I would like to make sure that I have a good solution for this problem before the project gets too big.