Skip to main content

NHibernate–Using record types

At one of my customers, we have been using NHibernate for a really long time. And although I think that with the latest Entity Framework Core, the feature set is almost on par, we are still using NHibernate today.

Of course, we want to use the newest C# features including Record types.

Let’s see if (and how) we can use record types in combination with NHibernate.

Here is a simple record type using positional parameters:

And the mapping code using Fluent NHibernate:

If we try to use this type in our application, NHibernate starts to complain with the following error message:

   ---- NHibernate.InvalidProxyTypeException : The following types may not be used as proxies:

    Tests.Domain.Category: type should have a visible (public or protected) no-argument constructor

    Tests.Domain.Category: method Deconstruct should be 'public/protected virtual' or 'protected internal virtual'

    Tests.Domain.Category: method get_Id should be 'public/protected virtual' or 'protected internal virtual'

    Tests.Domain.Category: method set_Id should be 'public/protected virtual' or 'protected internal virtual'

    Tests.Domain.Category: method get_CategoryName should be 'public/protected virtual' or 'protected internal virtual'

    Tests.Domain.Category: method set_CategoryName should be 'public/protected virtual' or 'protected internal virtual'

    Tests.Domain.Category: method get_Description should be 'public/protected virtual' or 'protected internal virtual'

    Tests.Domain.Category: method set_Description should be 'public/protected virtual' or 'protected internal virtual'

This makes sense as in NHibernate by default lazy loading is enabled. To use lazy loading a proxy class need to be created and this requires that all properties are declared virtual.

In this case I don’t need lazy loading for this class, so let’s disable this in our mapping file:

This solves a part of the errors above. If we try to run our application again, we still got an error:

FluentNHibernate.Cfg.FluentConfigurationException : An invalid or incomplete configuration was used while creating a SessionFactory. Check PotentialReasons collection, and InnerException for more detail.

    ---- NHibernate.InstantiationException : Object class NHibernate.Tests.Domain.Category must declare a default (no-argument) constructor

NHibernate needs a (private) default constructor without arguments to be able to create the type. As we are using a positional Record type, only a constructor with the 3 properties as argument is available. Although some ‘hacks’ exist to get rid of this error in NHibernate, the easiest solution is to switch to the standard property syntax and introduce an extra constructor:

Popular posts from this blog

XUnit - Assert.Collection

A colleague asked me to take a look at the following code inside a test project: My first guess would be that this code checks that the specified condition(the contains) is true for every element in the list.  This turns out not to be the case. The Assert.Collection expects a list of element inspectors, one for every item in the list. The first inspector is used to check the first item, the second inspector the second item and so on. The number of inspectors should match the number of elements in the list. An example: The behavior I expected could be achieved using the Assert.All method:

Azure DevOps/ GitHub emoji

I’m really bad at remembering emoji’s. So here is cheat sheet with all emoji’s that can be used in tools that support the github emoji markdown markup: All credits go to rcaviers who created this list.

Angular --deploy-url and --base-href

As long you are running your Angular application at a root URL (e.g. www.myangularapp.com ) you don’t need to worry that much about either the ‘--deploy-url’ and ‘--base-href’ parameters. But once you want to serve your Angular application from a server sub folder(e.g. www.mywebsite.com/angularapp ) these parameters become important. --base-href If you deploy your Angular app to a subfolder, the ‘--base-href’ is important to generate the correct routes. This parameter will update the <base href> tag inside the index.html. For example, if the index.html is on the server at /angularapp/index.html , the base href should be set to <base href="/angularapp/"> . More information: https://angular.io/guide/deployment --deploy-url A second parameter that is important is ‘--deploy-url’. This parameter will update the generated url’s for our assets(scripts, css) inside the index.html. To make your assets available at /angularapp/, the deploy url should