Partial class support vs Specify a base class

Question

Partial class support vs Specify a base class

Laurent Guigon 311

Hi,
I asked this question a few months ago.

The answer explained the difference between the two approaches.

Today, I'm wondering what the best practice is:

Should I always use the "Specify a base class" approach?
Or perhaps combine it with the partial class approach?
Or even use partial classes that inherit from a base class?

What are your advice regarding the "code behind" design?

If the third way is the best, can you give me a code sample showing how to implement this ?

AgaveJoe 1,510 Reputation points

2023-07-30T10:41:09.64+00:00

You are asking a design question without providing the design intention! When it comes to design, the idea is to review feature definitions to determine which approach best fits a use case. In this case, the deciding factor is whether to use object oriented programming (base class) or not (partial class).

Inheritance enables a new classes to reuse, extend, and modify the behavior defined in a base class. If the design has a "type of" relationships then a base class (inheritance) is a possible design approach.

Inheritance - derive types to create more specialized behavior

A partial class is a single class spread across one or more files. But a partial class is still a single class.

Partial Classes and Methods (C# Programming Guide)

Code generators build a partial class so OOP is not forced on developers.
Laurent Guigon 311 Reputation points

2023-08-03T12:45:54.1966667+00:00

I just asked about Blazor and if there's a best practice regarding whether to specify a base class or use partial classes. I've seen tutorials with both the 'Specify a base class' pattern and the 'partial class support', and it's a bit confusing to me. I'd like to follow DRY (Don't Repeat Yourself) and SOLID principles as much as possible. In my opinion, partial class support will be the default implementation, and if I need inheritance, then I'll use the 'Specify a base class' pattern. However, I'm not aware of any recommendations about the best practices, so I'm seeking your help to clarify my understanding. I've been a .NET web developer for 14 years, and this is just an upgrade to my practices.
AgaveJoe 1,510 Reputation points

2023-08-03T14:01:24.5166667+00:00

Partial classes are a compiler feature to aid code maintenance.

Source code generators create partial classes so developers can add properties, methods, fields, etc to the class in a separate file. The code generator can run many times without overwriting the developer's changes.

Partial Classes and Methods (C# Programming Guide)

In my opinion, partial class support will be the default implementation, and if I need inheritance, then I'll use the 'Specify a base class' pattern.

I feel making every class a partial is unnecessary unless there is a valid code maintenance reason to do so.
Laurent Guigon 311 Reputation points

2023-08-04T09:40:12.3566667+00:00

So, you prefer to code your C# code directly in your .razor files? I prefer to separate the code and the HTML. Maybe it's a reminiscence of the old WebForms' code-behind pattern...

2 answers

Your answer

AgaveJoe 1,510 Reputation points

2023-07-30T10:41:09.64+00:00

You are asking a design question without providing the design intention! When it comes to design, the idea is to review feature definitions to determine which approach best fits a use case. In this case, the deciding factor is whether to use object oriented programming (base class) or not (partial class).

Inheritance enables a new classes to reuse, extend, and modify the behavior defined in a base class. If the design has a "type of" relationships then a base class (inheritance) is a possible design approach.

Inheritance - derive types to create more specialized behavior

A partial class is a single class spread across one or more files. But a partial class is still a single class.

Partial Classes and Methods (C# Programming Guide)

Code generators build a partial class so OOP is not forced on developers.
Laurent Guigon 311 Reputation points

2023-08-03T12:45:54.1966667+00:00

I just asked about Blazor and if there's a best practice regarding whether to specify a base class or use partial classes. I've seen tutorials with both the 'Specify a base class' pattern and the 'partial class support', and it's a bit confusing to me. I'd like to follow DRY (Don't Repeat Yourself) and SOLID principles as much as possible. In my opinion, partial class support will be the default implementation, and if I need inheritance, then I'll use the 'Specify a base class' pattern. However, I'm not aware of any recommendations about the best practices, so I'm seeking your help to clarify my understanding. I've been a .NET web developer for 14 years, and this is just an upgrade to my practices.
AgaveJoe 1,510 Reputation points

2023-08-03T14:01:24.5166667+00:00

Partial classes are a compiler feature to aid code maintenance.

Source code generators create partial classes so developers can add properties, methods, fields, etc to the class in a separate file. The code generator can run many times without overwriting the developer's changes.

Partial Classes and Methods (C# Programming Guide)

In my opinion, partial class support will be the default implementation, and if I need inheritance, then I'll use the 'Specify a base class' pattern.

I feel making every class a partial is unnecessary unless there is a valid code maintenance reason to do so.
Laurent Guigon 311 Reputation points

2023-08-04T09:40:12.3566667+00:00

So, you prefer to code your C# code directly in your .razor files? I prefer to separate the code and the HTML. Maybe it's a reminiscence of the old WebForms' code-behind pattern...

Answer 1

Bruce (SqlWork.com) 77,686 Volunteer Moderator

a base class is used for inheritance. Modern design practice is to avoid having a very deep inheritance tree, that is more than a base class and an inherited class. the main use case is a library class that allow user extension. as changes to the super classes can break an inherited class, this technique is considered fragile.

partial classes allow the class definition to be split into multiple files. the main use case, is customizing auto generated code. the autogenerated code can be regenerated without deleting the custom code.

interface design or composition is often preferred over inheritance.

also you can use extension methods to extend a class.

https://learn.microsoft.com/en-us/dotnet/csharp/programming-guide/classes-and-structs/extension-methods

Laurent Guigon 311 Reputation points

2023-08-03T12:53:34.58+00:00

I know it. I asked what is the best practice for Blazor implementation between the 'Specify a base class' pattern and the 'partial class support' pattern... 'Specify a base class,' okay, but why use inheritance while there's no polymorphism behind it? Maybe in the future, I'll use another class derived from this base class? Maybe in the future, I'll be the richest man on Earth (LOL)... So I'm just asking how you do it in your company to implement Blazor? What is the best way to handle this?
Bruce (SqlWork.com) 77,686 Reputation points Volunteer Moderator

2023-08-04T19:47:55.2266667+00:00

There is nothing unique about Blazor that affects design decisions. Razor pages use a base class that you could override (this was common with MVC controllers to get common properties and methods). But injection is probably a better solution.

as I stated partial classes best use case is to extend generated code, especially add properties. Probably any code generator you use will do this. Not a good use case otherwise.

I avoid class inheritance. Many use cases can be replaces by generics instead. You probably should be using interfaces rather than base classes.

so my recommendation is to avoid both base classes and partial classes. When you need them you will know.

Answer 2

Laurent Guigon 311

I found this topic on the net. If I understood it correctly, a good practice is to separate C# and Razor code by using a partial class (MyPage.razor + MyPage.razor.cs, which is the partial class). If you use the same instructions in several pages, then you should factorize it! Create a base class and use inheritance in the .razor.cs code.

Bruce (SqlWork.com) 77,686 Reputation points Volunteer Moderator

2023-08-09T18:06:26.3833333+00:00

razor page with a code behind is not really a partial class. the code behind defines the @model class. if named pagename.cshtml.cs, visual studio will group together, but you do not need to follow this convention. you may also want the models in a separate folder.

whether to use separate page model files is a preference. I think it encourages too much code in the page model vs separate modules. The razor code should just be the UI and the mapping of the page model to business objects and calling the injected business layer.

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Partial class support vs Specify a base class

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