Question

i have a existing table with a primary key over 3 columns (1 varchar and 2 integer).
How can i tell the entity framework to use this “key”.
Is it possible using the modelBuilder, attributes or is there another way ?

thanks!

Answer 1

In fluent api you must use anonymous type:

modelBuilder.Entity<YourType>()
            .HasKey(e => new 
                {
                    e.VarChar,
                    e.Int1,
                    e.Int2
                });

Other way is using data annotations:

public class YourType
{
    [Key, Column(Order = 0)]
    public string VarChar { get; set; }
    [Key, Column(Order = 1)]
    public int Int1 { get; set; }
    [Key, Column(Order = 2)]
    public int Int2 { get; set; }
}

In both scenarios order of columns is important. Once you try to use DbSet<YourType>.Find you will have to supply keys in the same order. EF also uses order internally.