requires a primary key to be defined 🟪 .NET

EF Core: The entity type 'X' requires a primary key to be defined

EF Core found an entity class without a key property it can recognise.

Seen on: .NET

Meaning

EF looks for Id or <TypeName>Id. Other names need [Key] or HasKey(); keyless query types need HasNoKey(). DTOs accidentally exposed as DbSet also trigger it.

Common causes

  • Key property not named Id/<Type>Id
  • Composite key not configured
  • Class meant to be keyless (view/query)
  • Non-entity class included as DbSet or navigation

⚡ Quick fix

  1. Add [Key] or modelBuilder.Entity<T>().HasKey(...)
  2. Use HasNoKey() for views
  3. Remove accidental DbSet/navigation

Detailed fix by platform

C#

  1. csharp
    modelBuilder.Entity<OrderLine>().HasKey(l => new { l.OrderId, l.LineNo });
modelBuilder.Entity<SalesReport>().HasNoKey().ToView("vw_sales");

How to diagnose

  1. Entity — Named in the error
  2. Key — Property naming

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