When dealing with "EF-Code First," how can I define Keys?

asp.net c#-4.0 code-first entity-framework


I get a ModelValidationException (at the bottom) when working with "EF-Code First". It wants me to define a Key but I'm not sure what exactly it means...

public class Unit
    Guid id;
    String public_id;
    String name;        
    bool deleted;

public class MyDataContext : DbContext
    public DbSet<Unit> Units { get; set; }

    protected override void OnModelCreating(ModelBuilder modelBuilder)

public class DataTests
    public void Test()
        MyDataContext database = new MyDataContext();
        var o = database.Units;

        Console.WriteLine(o.Count()); // This line throws!

System.Data.Entity.ModelConfiguration.ModelValidationException : One or more validation errors were detected during model generation:

System.Data.Edm.EdmEntityType: : EntityType 'Unit' has no key defined. Define the key for this EntityType.

System.Data.Edm.EdmEntitySet: EntityType: The EntitySet Units is based on type Unit that has no keys defined.

11/8/2012 10:53:46 AM

Accepted Answer

You need to use properties, not private local variables for all the fields that you want EF to create database fields for.

Public Guid Id {get; set;}

1/5/2011 10:24:24 AM

Popular Answer

Make your fields properties, and then use the [Key] attribute like this:

public Guid MyId { get; set; }

You will have to reference and import System.ComponentModel.DataAnnotations to get the KeyAttribute. More info can be found here.

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