Question

I have the two classes:

public class PartDefinition
{
    public int Id { get; set; }

    [Required]
    [MaxLength(10)]
    public string PartNumber { get; set; }

    [Required]
    public virtual Module Module { get; set; }
}

public class Module
{
    public int Id { get; set; }

    [Required]
    [MaxLength(10)]
    public string Name { get; set; }
}

Then I try to perform this action:

PartDefinition part = new PartDefinition(partNumber, module);
context.PartDefinitions.Add(part);
context.SaveChanges();

The module that I am passing to the new part definition already exists in the database. However, when I save the new part definition instead of adding the current module as a foreign key it inserts a completely new module.

How can I change this?

Answer 1

Since you do not have any [Key] attributes representing the primary keys in the database; it adds a new module every time. Try marking Id property with [Key] attribute.
Also try to use the same context instance while fetching module and inserting part.