Insert a null value in a numeric database column

cidnos · **Joined:** Fri Oct 06, 2006 1:25 pm **Posts:** 5

Hi
Perhaps somebody can help me here?
I'd like to add a null value in a numeric database column

I defined a property in a mapping file. It's type is float and is Is-null attribute is set to false
I defined too a property class with the same type

When i saved (Save instruction) my class, the property class is initialised to zero even if the database column can store a null value.

Is it possible to store null value with NHibernate?

Thanks for you help
Christophe

cidnos · **Joined:** Fri Oct 06, 2006 1:25 pm **Posts:** 5

Another information: I work with Visual studio 2003 and the 1.1 .Net framework version

subdigital · **Posted:** Fri Oct 06, 2006 5:16 pm

In your mapping, you specify isNull=false, which means the column does not allow nulls.

The 2nd thing you should do is implement a custom IUserType. In .NET 2.0 we have nullable types, and NHibernate can work with that.

In 1.1, however, if you create a custom type you can specify a magic value that MEANS null, for example Int32.MinValue. If you initialize your integers to this, and create a NullIntType that implements IUserType correctly, then you can specify that when setting a value to a command's parameter, if the value is ####, then use DBNull.Value, otherwise use the value of the integer. Likewise when the iusertype gives you a datareader, you pull the value from the reader and convert it to the integer.

Hope this helps.

luedi · **Joined:** Tue Feb 21, 2006 9:50 am **Posts:** 107

you also can use the NullableType library. If you use NHibernate 1.0.2 you have to download the NHibernate Contrib package. In NHibernate 1.2 Beta it is included. Your code should look like this:

Code:

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.0" assembly="MyAssembly" namespace="MyNamespace">
   <class name="MyClass" table="My_Table">
      ...
      <property name="NullableFloat" column="Float_Value" type="Nullables.NHibernate.NullableDoubleType, Nullables.NHibernate" not-null="false" />
      ...
   </class>
</hibernate-mapping>

Code:

using Nullables;

namespace MyNamespace
{
   public sealed class MyClass : BaseInternalModel
   {
      ...
      private NullableDouble mNullableFloat;
      ...
      public MyClass()
      {
      }
      ...

      public NullableDouble NullableFloat
      {
         get { return mNullableFloat; }
         set { mNullableFloat = value; }
      }
      ...
   }
}