Closed arteny closed 6 months ago
And I meet this issue in real usage now with EFCore. As for me, it breaks all concepts of ValueObject. When I use this code:
await db.Exposures.Where(x => x.Market.Id == market.Id).ExecuteDeleteAsync();
there are no errors or warnings during compilation, but at execution time, I get the exception:
System.InvalidCastException: Invalid cast from 'System.String' to 'Domain.Enums.MarketId'
market.Id is string here, so to get it working i need to change it to MarketId.From(market.Id)
, but I expected to know this before running my program.
MarketId type has the following definition:
[ValueObject<string>(conversions: Conversions.EfCoreValueConverter | Conversions.Default)]
Hi @arteny , this is correct behaviour. Or at least it's behaviour that has been there since inception.
Vogen generates the following equality methods for all underlying types. For a string
it's
public static bool operator ==(EventId left, string right) => Equals(left.Value, right);
public static bool operator !=(EventId left, string right) => !Equals(left.Value, right);
As for me, it breaks all concepts of ValueObject
Two of the main concepts of a Value Object are:
For the latter, encapsulation isn't broken; Equals(this, string other)
doesn't allow you to access this
if it isn't valid, and the comparison to the underlying string
doesn't create any other value object.
I think that EF is taking your where
expression and rewriting it in such a way that the Equals is being ignored and a direct cast is used instead.
Looking online reveals lots of issues related to comparisons in expressions (most are related to casing of the string).
There are a few additional things that you need to do before using Vogen types with EF. These are described in this How To article. I hope this solves your problem. If you could let me have some feedback on that article (or better still, modify it if there's something missing/incorrect/confusing), that'd be great.
Closing this as I'm confident that the additional setup shown in the documentation will solve this issue, but please let me know if it doesn't.
Is there a way to opt out of this? I have a value object which is a record struct backed by a string. I only want these two structs to be able to be compared, as comparing one with a string allows comparing a a non-nullable struct to null (which I'd like to prevent compile time).
In this case it allows
[ValueObject<string>]
public partial record struct MyThing;
MyThing.From("abc") == null;
Describe the bug
Not sure that it is correct behaior for ValueObject as strong typed value
There is no any compilation error.
Steps to reproduce
Compile.
Expected behaviour
Compilation error.