CODEWITHSUNDEEP
c#typescasting
zhuber
zhuber

Reputation: 5524

Assign another type to specific type

I have base class thats inherited by multiple classes

public class Animal
{
    public int Id { get; set; }

    public static Animal Get(int id)
    {
        return ...
    }
}

public class Cat : Animal
{
    public CatPayload Payload { get; set; }
}

public class Dog : Animal
{
    public DogPayload Payload { get; set; }
}

public class CatPayload
{
    public int Lives { get; set; }
}

public class DogPayload
{
    public bool IsDangerous { get; set; }
}

I store only Animal identifier in the database, so when I'm getting it using static method I get instance of Animal and I can't get strongly-typed instance of Payload. What would be the best way to implement this? Only thing I currently have on mind is checking type of animal instance if it matches any of the subclasses, but I'm not sure if there some simpler way?

Upvotes: 0

Views: 37

Answers (2)

Martin Staufcik
Martin Staufcik

Reputation: 9490

1) Inheritance is supported in EF. This guide shows how it can be done:

Tutorial: Implement Inheritance with EF in an ASP.NET MVC 5 app

2) You might also consider using a flat structure for your data model in which the entities are referencing each other with foreign keys:

public class Cat
{
    public int AnimalId { get; set; }

    [ForeignKey(nameof(AccountId))]
    public Animal Animal { get; set; }

    public CatPayload Payload { get; set; }
}

3) For the payload you might use a string property for persistance containing json of the serialized class:

[NotMapped]
[JsonIgnore]
CatPayload Payload { get; set; }

public string PayloadJson
{
    get => Payload == null ? null : JsonConvert.SerializeObject(Payload);
    set => Payload = value == null ? null : JsonConvert.DeserializeObject<CatPayload>(value);
}

Upvotes: 1

sommmen
sommmen

Reputation: 7608

I find your answer lacking a bit in details, so i don't know if this helps, but otherwise please extend your answer with more details, especially the parts of code that use these classes.

You can easily check with pattern matching:


// Creates a Cat, casts to an animal type
Animal myAnimal = new Cat(3);

if(myAnimal is Cat castedAnimalToCat)
{
   // myCat is Animal returned true, which means we have a cat object.
   // castedAnimalToCat is now a new variable of type Cat
   Console.WriteLine($"{castedAnimalToCat.CatPayload}");
}

if(myAnimal is Dog castedAnimalToDog)
{
  // ...
}

So somwhere in your database logic you can cast this to the right operand. You can do some more fancier things with reflection, but your concern is always time safety and complexity with that.

Upvotes: 1

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