Question

I am new to ASP.net MVC. I am trying to create a viewmodel to display a join of data. Here is some example code:

   public class Person
{
    [Key]
    public int ID { get; set; }
    public string Name { get; set; }

    public ICollection<Relative> Relatives { get; set; }

}

public class Relative
{
    [Key]
    public int ID {get; set; }
    public Person Person { get; set; }
    public RelationType RelationType { get; set; }
}

public class RelationType
{
    [Key]
    public int ID { get; set; }
    public string Description { get; set; }
}

public class PersonViewModel
{
    public string Name { get; set; }
    public ICollection<string> RelativeNames { get; set; }
    public ICollection<string> RelativeTypes { get; set; }
}

public class PersonContext : DbContext
{
    public DbSet<PersonViewModel> people { get; set; }
}

When I try to create my controller through Visual Studio, I get the following error:

Unable to retrieve metadata for PersonViewModel. One or more validations errors were detected during generation:
EntityType ‘PersonViewModel’ has no key defined. Define the key for this EntityType.

Answer 1

The error is self explanatory. You need to add an Id field to the PersonViewModel which will have to be decorated with [Key] as you have rightly done in the classes above.