How to extend entity class?

Question

I'm using Entity Framework and Mysql. And I have Entity classes for each tables.

But I do not know how to extend fields into entity class that does not defined in DB .

For example) I have test table and the table have id, price and qty fields.

My entity class is like this,

[Table('test')]
public class Test
{
  [Key]
  public int id {get; set;}
  public decimal price {get; set;}
  public int qty {get; set;}
}

Now, I need subtotal field in Test class. (for some reason, I can not modify DB )

so I try to make the Test class as Partial class,

[Table('test')]
public partial class Test
{
  [Key]
  public int id {get; set;}
  public decimal price {get; set;}
  public int qty {get; set;}
}

public partial class Test 
{
  public decimal? subTotal {get; set;}
}

Then I got an error : It say, 'Unknown column 'Extent1.subTotal' in 'field list''

Anybody know, How can I add the subTotal field into Test class without changing DB structure?

Please advice me.

Answer 1

Use the NotMappedAttribute for any properties you want to have in your model, but do not want Entity Framework to map to your database.

 [Table('test')]
    public class Test
    {
      [Key]
      public int id {get; set;}
      public decimal price {get; set;}
      public int qty {get; set;}
      [NotMapped]
      public decimal? subTotal {get; set;}
    }