nhibernate subclass - zero guid in not used column instead of null

Question

I have an issue with a two subclasses using the same table and same fields. Even though the generated table has this fields as nullable uniqueidentifiers, when I save the one record that does not use the third column, then the created field has a value of "000000000-0000-0000-0000-000000000000" instead of NULL. Other parts of application require this place to be null. Here's the code. What's wrong?

 <?xml version="1.0" encoding="utf-8" ?> <hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" assembly=".." namespace="..."> <class name="TEST" table="..." discriminator-value="not null"> <id name="Id" column="tID"> <generator class="assigned" /> </id> <discriminator column="iTestTypeID" type="Int32" not-null="true"/> <property name="TotalScore" column="fTotalScore"/> <property name="IsTimedOut" column="bTimedOut"/> </hibernate-mapping> <?xml version="1.0" encoding="utf-8" ?> <hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" assembly=".." namespace="..."> <subclass name="TestA" extends="TEST" discriminator-value="3"> <many-to-one name="Department" column="uTestCriteria01" cascade="save-update" not-null="false" /> <many-to-one name="Building" column="uTestCriteria02" cascade="save-update" not-null="false" /> </subclass> </hibernate-mapping> <?xml version="1.0" encoding="utf-8" ?> <hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" assembly=".." namespace="..."> <subclass name="TestB" extends="TEST" discriminator-value="3"> <many-to-one name="Building" column="uTestCriteria01" cascade="save-update" not-null="false" /> <many-to-one name="Floor" column="uTestCriteria02" cascade="save-update" not-null="false" /> <many-to-one name="Room" column="uTestCriteria03" cascade="save-update" not-null="false" /> </subclass> </hibernate-mapping>

Community · Accepted Answer · 2017-05-23 10:09:46Z

My guess would be that your objects aren't using nullable types.

Do you have the types defined like this:

public class A { public Guid? field { get; set; } }

Take a look at this StackOverflow article for an explanation:
How can I default a parameter to Guid.Empty in C#?

Also in your question I would list the specific field(s) you are talking about so there is no confusion and post the code for your objects that are tied to this mapping.

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