Adding additional properties to an entity framewor

问题:

I am using ASP.NET MVC 3 and Entity Framework code first CTP 5. I was wondering if it is possible to add additional properties that is not mapped to a table column?

I haved a News class and it is defined as such:

public class News : Entity
{
   public int NewsId { get; set; }
   public string Title { get; set; }
   public string Body { get; set; }
   public bool Active { get; set; }
}

My database context class:

public class MyContext : DbContext
{
   public DbSet<News> Newses { get; set; }
}

In the entity class I have a property defined like:

public IList<RuleViolation> RuleViolations { get; set; }

I have not code this part yet, but I want all broken rules to be added to this list when the object is validated. The error that I am getting is:

One or more validation errors were detected during model generation:

    System.Data.Edm.EdmEntityType: : EntityType 'RuleViolation' has no key defined. Define the key for this EntityType.
    System.Data.Edm.EdmEntitySet: EntityType: The EntitySet RuleViolations is based on type RuleViolation that has no keys defined.

Here is my reposity code:

public News FindById(int newsId)
{
   return context.Database.SqlQuery<News>("News_FindById @NewsId",
      new SqlParameter("NewsId", newsId)).FirstOrDefault();
}

UPDATE 2011-03-02:

Here is my Entity class:

public class Entity
{
   public IList<RuleViolation> RuleViolations { get; set; }

   public bool Validate()
   {
      // Still needs to be coded
      bool isValid = true;

      return isValid;
   }
}

Here is my RuleViolation class:

public class RuleViolation
{
   public RuleViolation(string parameterName, string errorMessage)
   {
      ParameterName = parameterName;
      ErrorMessage = errorMessage;
   }

   public string ParameterName { get; set; }
   public string ErrorMessage { get; set; }
}

Here is my context class:

public class MyContext : DbContext
{
   public DbSet<News> Newses { get; set; }

   protected override void OnModelCreating(ModelBuilder modelBuilder)
   {
      modelBuilder.Entity<News>().Ignore(n => n.RuleViolations);
   }
}

回答1:

You can ignore the type using Fluent API by adding an ignore rule to your OnModelCreating method of your MyContext class

public class MyContext : DbContext {

  public DbSet<News> Newses { get; set; }

  protected override void OnModelCreating(ModelBuilder builder) {

    builder.Ignore<RuleViolation>()

  }

}

Or you can ignore the property by using the NotMapped attribute

public class Enitity {

  [NotMapped]
  public IList<RuleViolation> RuleViolations { get; set; }

  //other properties here

}

and then Entity Framework will ignore the property.

回答2:

You can also use:

[NotMapped]
public IList<RuleViolation> RuleViolations { get; set; }

To use NotMapped you have to add using System.ComponentModel.DataAnnotations;

Edit:

Now I see that you want to avoid mapping property from base class. It doesn't work with OnModelCreating - it is confirmed bug in CTP5 (I will try to find link later). I'm not sure if it works with NotMappedAttribute. This attribute is just other approach to achieve the same result.