为什么我们需要DTO / VIewModels而不是在MVC Core中使用部分类？

Question

I have an application in MVC CORE and in this application, i am using DTO/ViewModels. First I get from database and fill into the viewModels/DTOs. DTOs are more helpful because we can customize it in our own way rather than Microsoft Entity Framework pure generated poco classes. We can place data annotations, make more properties and can utilize them for more customization.

But now i am facing the performance issues from this layer/DTO/ViewModel.

Because For such large data, c# loops are much slowing down my application.

Can't/Shouldn't i use the Partial Classes and write data annotations and write our own properties there.

What will be the issue in it ?

Answer 1

Because For such large data, c# loops are much slowing down my application

Use restrictions in queries. I dont know why you need 1,000,000 records at once. if you need the 1,000,000 records do paging. Is not the fact that you are using EF objects directly that is going to give you performance.

You can use the partial classes in EF objects and add new properties and add them Annotations and all that, but my advice is don't use EF objects across your application. You loose abstraction, low coupling, your Domain model shouldn't be aware of infrastructure concerns(EF). Model should be focus on Model. Look at Uncle Bob, Clean Architecure https://8thlight.com/blog/uncle-bob/2012/08/13/the-clean-architecture.html for some insight. After reading you figure it out, why using EF objects could not be such a great idea.

This is a very vast topic to talk about. Hope help you with my 5 cents