NHibernate LINQ查询不支持指定的方法错误

Question

I am new to NHibernate and while exploring it I got into trouble with the following query which gives me a "Specified method is not supported." error, any ideas why?

var merchantSite = session.Query<MerchantSite>().FirstOrDefault(x => x.Site.Id == SiteId);
var customers = session.Query<Customer>().Where(x => x.Transaction.Any<Transaction>(y => merchantSite.Transaction.Any<Transaction>(c => c.Id == y.Id))).ToList();

Both MerchantSite and Transaction have a list of objects of type Transaction.

There must be someone out there who has been in the similar situation, please share with us your experience, what should we do in this situation?

Thanks in advance!

Answer 1

当您执行ToList调用时，nHibernate正在构建运行查询所需的SQL，并且基本上是在将其转换为单个SQL调用时遇到麻烦。

Answer 2

If x.Site is null, then you'd get "specific method is not supported." You could try writing

FirstOrDefault(x => x.Site != null && x.Site.Id == SiteId);

or using C# 6

FirstOrDefault(x => x.Site?.Id == SiteId);