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What is a value converter in EF Core?

Entity Framework & EF Core Modelling Intermediate 2–3 Yrs3–5 Yrs Conceptual 1 min read

Quick Answer

A value converter transforms a property between its CLR representation and how it's stored in the column. Use HasConversion to store an enum as a string, a value object as its primitive, a list as JSON, or to encrypt a column — the entity keeps the nice type, the database gets the storable form.

A value converter sits between the property type in your code and the column type in the database. The everyday use is HasConversion<string>() on an enum so the database stores “Active” instead of an int that breaks if someone reorders the enum. It's also how you persist a value object like an EmailAddress as a plain string, or store a small list as JSON, or transparently encrypt a column. The thing to watch is that filtering on a converted column doesn't always translate to SQL cleanly.

  • builder.Property(o => o.Status).HasConversion<string>(); — enum stored as text (readable in the DB, safe against reordering).
  • HasConversion(v => v.Value, v => new EmailAddress(v)) — a value object stored as a string.
  • Built-in converters exist for common cases; you can also write an EncryptingConverter.
  • Caveat: a converted column can't always be translated in a WHERE the way a native column can — check the generated SQL, and prefer converting to a type the provider understands.
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