实体框架：具有相同类问题的两个属性

Question

As I am not so experienced with EntityFramwork, I am facing problems. I need to track which user created the Transaction and which user modified that transaction. This means I have two properties having the same class.

Here is the list of the properties in Transaction Class:

public virtual System.DateTime DateCreated { get; set; }
public virtual System.DateTime DateModified { get; set; }
public virtual bool IsDeleted { get; set; }
public virtual bool IsActive { get; set; }
public virtual string Description { get; set; }

public virtual User CreatedBy { get; set; }
public virtual User ModifiedBy { get; set; }

Whenever the context.SaveChanges() is called i get the following exception:

Unable to determine the principal end of an association between the types 'Model.Entities.User' and 'Model.Entities.User'. The principal end of this association must be explicitly configured using either the relationship fluent API or data annotations.

Answer 1

You should override the OnModelCreating method in your dbcontext class and add the following code

 modelBuilder.Entity<Transaction)()
 .HasOptional<User>(x => x.CreatedBy);


 modelBuilder.Entity<Transaction)()
 .HasOptional<User>(x => x.ModifiedBy);

Of course HasOptional can also be hasrequired.