InvalidOperationException: The property 'Company.Id' could not be mapped because it is of type 'CompanyId', which is not a supported primitive type or a valid entity type

[MrYossu]

Just trying to get the hang of this library, and am running into a problem.

I set up a simple Blazor app that uses EF Core against SQL Server. I added a model for a company, and a VO for the Id...

[ValueObject<int>]
public partial struct CompanyId;

public class Company {
  public CompanyId Id { get; set; }
  public string Name { get; set; } = "";
}

In order to make this work with EF, I followed the tips on this wiki page. I added the extension class and called it from the DbContext class.

However, when I try the following...

CompanyId id = CompanyId.From(1);
Company? company = await _context.Companies.SingleOrDefaultAsync(c => c.Id == id);

...then I get the exception mention in the title.

I did some digging around in the extension method, and added a load of logging...

  public static void ApplyVogenEfConvertersFromAssembly(this ModelConfigurationBuilder configurationBuilder, Assembly assembly) {
    Type[] types = assembly.GetTypes();
    foreach (Type type in types) {
      if (IsVogenValueObject(type)) {
        if (TryGetEfValueConverter(type, out Type? efCoreConverterType)) {
          Console.WriteLine($"ApplyVogenEfConvertersFromAssembly - adding type {type.Name}");
          configurationBuilder
            .Properties(type)
            .HaveConversion(efCoreConverterType);
        } else {
          Console.WriteLine($"ApplyVogenEfConvertersFromAssembly - type not found");
        }
      }
    }
  }

  private static bool TryGetEfValueConverter(Type type, [NotNullWhen(true)] out Type? efCoreConverterType) {
    Type[] inner = type.GetNestedTypes();
    if (type == typeof(CompanyId)) {
      Console.WriteLine($"TryGetEfValueConverter(CompanyId) - nested types ({inner.Length})...");
      foreach (Type innerType in inner) {
        Console.WriteLine($"  Name            : {innerType.Name}");
        Console.WriteLine($"  IsAssignableFrom? {typeof(ValueConverter).IsAssignableFrom(innerType)}");
        Console.WriteLine($"  Equals          : {"EfCoreValueConverter".Equals(innerType.Name, StringComparison.Ordinal)}");
      }
    }
    foreach (Type innerType in inner) {
      if (!typeof(ValueConverter).IsAssignableFrom(innerType) || !"EfCoreValueConverter".Equals(innerType.Name, StringComparison.Ordinal)) {
        continue;
      }
      efCoreConverterType = innerType;
      return true;
    }
    efCoreConverterType = null;
    return false;
  }

  private static bool IsVogenValueObject(MemberInfo targetType) =>
    "Vogen".Equals(targetType.GetCustomAttribute<GeneratedCodeAttribute>()?.Tool, StringComparison.Ordinal);

The only significant code change is that I split the if statement in the first method to cut down on the logging for non-Vogen types.

When the code runs, I get the following output...

TryGetEfValueConverter(CompanyId) - nested types (1)...
Name : CompanyIdSystemTextJsonConverter
IsAssignableFrom? False
Equals : False
ApplyVogenEfConvertersFromAssembly - type not found

So I guess the exception is caused because it can't find a converter. The question is, why can't it find a converter? As far as I can see, I did everything according to the wiki.

Anyone able to explain what I did wrong? Thanks

[MrYossu]

OK, found the issue in the wiki!.

I changed the VO to include the converter...

[ValueObject<int>(conversions: Conversions.EfCoreValueConverter)]
public partial struct CompanyId;

,,,and it worked 😎[*].

Hope this helps someone.

[*] As I was doing this on an existing database (I started off using a plain int for the Id), updating the database gave an error...

To change the IDENTITY property of a column, the column needs to be dropped and recreated.

In my case, this was a test app, so I just dropped the database, deleted all the migrations and started again, but that might not always be practical.