FieldConverter and DbNull

Hello,

I implemented a FieldConvertor, however it never seens to get called when the database value is DbNull.  This poses a problem if the CLR type on the entity is non-nullable.  What I'd like to do instead is to support some default value if the database value is null.  Is this possible?

Thanks,

Werner

I've not been able to reproduce this problem.  I tested loading from a nullable database column into a int field using the following converter:

    public class NIConverter : IFieldConverter
    {
      public object ConvertFromDatabase(object databaseValue)
      {
        if (databaseValue == DBNull.Value)
        {
          Console.WriteLine("nullity null null");
          return 73875;
        }
        return (int)databaseValue;
      }

      public object ConvertToDatabase(object value)
      {
        int i = (int)value;
        if (i == 73875)
        {
          return DBNull.Value;
        }
        return i;
      }
    }

The "DBNull" branch was taken and I saw the default value appearing in the materialised entities.

Could you provide us with a minimal schema and NUnit test or console application that exhibits the problem?  Thanks!

Here is my code snippet. 

   public sealed class NotificationChannelConvertor : Mindscape.LightSpeed.FieldConverters.FieldConverter<int, NotificationChannel>
    {
        protected override NotificationChannel ConvertFromDatabase(int databaseValue)
        {
            return (NotificationChannel)databaseValue;
        }

        protected override int ConvertToDatabase(NotificationChannel value)
        {
            return (int)value;
        }
    }

Werner

Your field converter is using the strong-typed FieldConverter<TDatabase, TModel> with a TDatabase of int, but your database contains non-int values.  This is causing casting errors; there is no way we can pass a DBNull.Value or even a null into your ConvertFromDatabase method because the argument type does not permit it.  Change your class to inherit either from FieldConverter<object, NotificationChannel> or directly from IFieldConverter.  You will then be able to handle the DBNull case to return a suitable value (see my post above for an example).

Thanks Ivan,  I'll use IFieldConvertor instead. 

It would be useful to have a virtual method I can override in the strongly-typed FieldConvertor. By default FieldConvertor can return the default value for TModel. The strongly-typed FieldConvertor is simpler to implement and requires less code.