How do I get a property's original value while validating, in EF Core?

问题

In EF Core, there is a neat way to perform entity validation using IValidatableObject.

During validation I have the current value, but I also need access to the original value.

This is the validation method:

public IEnumerable<ValidationResult> Validate(ValidationContext validationContext) { }

Is there some way to get access to the object's original values as well? I think the key is in ValidationContext but I'm not sure how.

来源：https://stackoverflow.com/questions/41771376/how-do-i-get-a-propertys-original-value-while-validating-in-ef-core