Hi,

I'm trying to map a private field in my class using NHibernate mapping attributes in C#.

It works fine when I use a public property, but when I switch to the private field belonging to that property I get the following exceptions:
{"Problem trying to set property type by reflection"} >
{"Could not find a getter for property 'user_ID' in class 'HibernateTest.User'"}

Apparently NHibernate.Mappings always explicitly looks for properties.
I also noticed that NHibernate.Mappings seems to ignore the C# entities to which the mapping attributes are added, as if they are simply piled together.
There are numerous mentions on the internet about the ability to map private fields, but I can't find a single example.

Your help is much appreciated.
Regards, Tonn

To map to a field you need to specify it using the access attribute="field" as the default is property.

<property name="user_ID"
column="user_id"
type="System.String"
access="field" />

It should not matter if the field or property is private, protected or public.
Also, if you flip back and forth in your mapping, just make sure you update the name as well (so that it points to the actual field or property name).

class User{
private string user_ID;

public string User_ID{
get{return user_ID;}
}

In this case if you put:
<property name="User_ID"
column="user_id"
type="System.String"
access="field" />

you would get errors because the field is user_ID not User_ID. (I've done that a few times when I don't want to have a set for a property)

Sorry I guess you want to use the PropertyAttribute right in the class.

class User{

[NHibernate.Mapping.Attributes.PropertyAttribute(
column="user_id", type="System.String", access="field")]
private string user_id;

public string User_ID{
get{return user_id;}
}
}

Hope that helps

I have a question regarding mapping to the field via the xxx.hbm.xml file.

I have a base class that all my persistent classes inherit. This class contains the primary key _Id field.

Since this field is not part of the subclasses, can I still map to the field or do I need a private property that only NHibernate uses to set this value?

Since I'm using native sequening, I don't want anyone to be able to provide the Id value directly.

Hi Padlewski,
Spot on! Thanks very much.


gcook,
Now that I've got it working, I have no problem moving my (primary key) id field and id property to a base class. It still works with no additional tweaking.

Hi gcook1,

You can access a field in an inheritence structure. Also if your using .NET 2.0 you can have a public getter and a protected or private setter. Because your extending off of your base class, you will have to make the field or the setter protected so the child classes can access the data (but I'm not 100% sure).

Also, if you want to use lazy loading they have to be virtual.

Hope this answers your question,
Darin

Actually,

I was able to keep the attributes of my base class (Id) private and NHibernate is still able to map them direct-to-field instead of going through the properties.

This is the method I prefer and is consistent with one of the more popular ORM tools in Java TOPLink for Java.

Now more than ever, I'm happy with my choice to use NHibernate.