Passing an inherited class into a method help

Question

User1034446946 posted

I have static class which accepts a List of an inherited class, when i build it to accept a single class it works,however i need ti accept multiple,and in this can I can't get it to work any suggestions?

Answer 1

User303363814 posted

I can't get it to work

Can you add some more detail?  What have you tried?  What was the error?

There are a few different things that you might be trying to do and they have different solutions.  It is easier to explain with a specific example.  So, please, can we see some code of what you have tried?

Answer 2

User-1174608757 posted

Hi EnenDaveyBoy,

According to your description ,static class couldn't be instantiated and inherited. You should use it as a static object.So, if you have met the problem.Could you please share your codes?It will help us to solve your problem.

Best Regards

Wei 

 

Answer 3

User1034446946 posted

public modelc :modelb
{}

public modelb : modela
{}

public modela
{
public int Id {get;set;}
}

public static class Helper
{
public static List<T> Map<T>(this List<T> entities, Guid primaryId, IList<modela> confirmedEntities) where T : someOtherModel
{
return entities;
}
}

this works

var i = new modelc();
entity.SomeNaviagtionEntity.Map(1, i);

but this doesn't

var i =new List<modelc>();

entity.SomeNavigationEntity.Map(1, i);

but i need the second one to work,any suggestions would be appriciated

I am trying to manually map many to many relationships in .netcore 2.1 ef, i am build a generic static class to map it, to the inherited class

Answer 4

User475983607 posted

There are many issues with this design.  The main issue is you are building an extension method which requires a static class.  An extension method is a way to add functionality to an existing type without making changes to the existing source code. 

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

The other issues with the code shown is you cannot inherit from a static class and a static class by definition cannot have members.

A minor issue is you can replace List<T> just T.  

Can you explain what problem "manually mapping many-to-many relationships" solves?   The relationship is exposed through the navigation properties and for the most part simply known.  

Answer 5

User1034446946 posted

There are many issues with this design.  The main issue is you are building an extension method which requires a static class.  An extension method is a way to add functionality to an existing type without making changes to the existing source code. 

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

The other issues with the code shown is you cannot inherit from a static class and a static class by definition cannot have members.

A minor issue is you can replace List<T> just T.  

Can you explain what problem "manually mapping many-to-many relationships" solves?   The relationship is exposed through the navigation properties and for the most part simply known.  

Sorry I added additional formatting to my example to give a better example, I am not mapping inhertiance from a static class, the classes are all just model classes which inheriate fromeach other,the static class is just a helper toholdmy mapping.

I don'tlike automapper,when models get complex, i spend all my timeon automapper telling it what not to do,and I don'tmind building the maps it's simple enough.

According to everything I have read and pluralsight, EF core at this time doesn't automatically map many to many in the same way as EF 6, so i need to build the navigation model,and I don't want to build a helper class for each time I have a many to many relationship that needs mapping.

Answer 6

User475983607 posted

Sorry I added additional formatting to my example to give a better example, I am not mapping inhertiance from a static class, the classes are all just model classes which inheriate fromeach other,the static class is just a helper toholdmy mapping.

You changed the original code.

I don'tlike automapper,when models get complex, i spend all my timeon automapper telling it what not to do,and I don'tmind building the maps it's simple enough.

You're not a fan of automapper.  Are you building a similar API?

According to everything I have read and pluralsight, EF core at this time doesn't automatically map many to many in the same way as EF 6, so i need to build the navigation model,and I don't want to build a helper class for each time I have a many to many relationship that needs mapping.

I use EF Core in a project with many-to-many relationships.  The many-to-many works according to the docs.  Is the problem you do not like adding the "join" entity?

Many-to-many relationships without an entity class to represent the join table are not yet supported. However, you can represent a many-to-many relationship by including an entity class for the join table and mapping two separate one-to-many relationships.

If so, it looks like EF Core 3.0 will have this feature but it does not stop you from creating a many-to-many now.  With all that being said, are you build this feature too?

Answer 7

User1034446946 posted

I am just using simple static extension classes to map,super simple, i wish I was clever enough to build my own API for mapping.

I have the many many relationship built,I just need to convert my viewModels to entites and then link the many to many,I forgot I don't need the original entity, as you didn't with EF,so I have converted it to a simplelist of ids.

I heard that it will be EF core 3 forits added, but nothing is set in stone as yet.

Although I would stilllive the know,why I can add a collection of an inherinted class to a method.

Answer 8

User475983607 posted

EnenDaveyBoy

I am just using simple static extension classes to map,super simple, i wish I was clever enough to build my own API for mapping.

I have the many many relationship built,I just need to convert my viewModels to entites and then link the many to many,I forgot I don't need the original entity, as you didn't with EF,so I have converted it to a simplelist of ids.

I heard that it will be EF core 3 forits added, but nothing is set in stone as yet.

Although I would stilllive the know,why I can add a collection of an inherinted class to a method.

If I understand, the actual issue is populating an an EF entity from a ViewModel?  Can you share the ViewModel and entities or a sample that reproduces this issue?  

Maybe this tutorial will help.

https://docs.microsoft.com/en-us/aspnet/core/data/ef-mvc/complex-data-model?view=aspnetcore-2.2

https://docs.microsoft.com/en-us/aspnet/core/data/ef-mvc/update-related-data?view=aspnetcore-2.2

Answer 9

User303363814 posted

I'm not 100% sure what you are trying to do since the text you have shown is a long way from being a runnable sample (a runnable sample that anyone can use is a great help to people trying to solve your problem).

But … try defining Map like this

public static List<T> Map<T,U>(
                      this List<T> entities,
                      Guid primaryId,
                      IList<U> confirmedEntities)
                         where T : someOtherModel
                         where U : modela
{
   return entities;
}