C
C#•4w ago
biohazrd

Generics w/ EF Core

I have an API that I don't control that looks something like this: 
public interface ICategorized { public int CategoryId { get; set; } }
public interface ITypeA { }
public interface ITypeB { }
public class CategoryA : ICategorized, ITypeA { public int CategoryId { get; set; } }
public class StreamA : ICategorized, ITypeA { public int CategoryId { get; set; } }
public class CategoryB : ICategorized, ITypeB { public int CategoryId { get; set; } }
public class StreamB : ICategorized, ITypeB { public int CategoryId { get; set; } }
public interface ICategorized { public int CategoryId { get; set; } }
public interface ITypeA { }
public interface ITypeB { }
public class CategoryA : ICategorized, ITypeA { public int CategoryId { get; set; } }
public class StreamA : ICategorized, ITypeA { public int CategoryId { get; set; } }
public class CategoryB : ICategorized, ITypeB { public int CategoryId { get; set; } }
public class StreamB : ICategorized, ITypeB { public int CategoryId { get; set; } }
I want to be able to create and store Filter objects in my database: 
public class FilterA { public int CategoryId { get; set; } }
public class FilterB { public int CategoryId { get; set; } }
public DbSet<FilterA> AFilters { get; set; }
public DbSet<FilterB> BFilters { get; set; }
public class FilterA { public int CategoryId { get; set; } }
public class FilterB { public int CategoryId { get; set; } }
public DbSet<FilterA> AFilters { get; set; }
public DbSet<FilterB> BFilters { get; set; }
However, when trying to use generic methods, I can't access the DbSet for the particular filter that I need: 
public IEnumerable<T> Filter<T>(this IEnumerable<T> items) where T : ICategorized
{
  // Doesnt work because I don't have DbSets of CategoryA/StreamA or B
  var filters = context.Set<T>().ToList();

  // Doesnt work because cant do pattern matching on generic type parameters and also ick
  if (T is A)
  {
    var filters = context.Set<FilterA>().ToList();
  }
}
public IEnumerable<T> Filter<T>(this IEnumerable<T> items) where T : ICategorized
{
  // Doesnt work because I don't have DbSets of CategoryA/StreamA or B
  var filters = context.Set<T>().ToList();

  // Doesnt work because cant do pattern matching on generic type parameters and also ick
  if (T is A)
  {
    var filters = context.Set<FilterA>().ToList();
  }
}
Basically, I want to easily be able to retrieve (or add) the appropriate Filter from my database, while keeping my various methods generic
2 Replies
ero
ero•4w ago
are you looking for if (typeof(T) == typeof(A))?
Sehra
Sehra•4w ago
maybe consider TPH as well https://learn.microsoft.com/en-us/ef/core/modeling/inheritance#table-per-hierarchy-and-discriminator-configuration
Inheritance - EF Core
How to configure entity type inheritance using Entity Framework Core

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