biohazrd Posts - Answer Overflow

biohazrd

•Created by biohazrd on 2/12/2025 in #help

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

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