Ok, I had a really hard to track down problem, and I couldn't find
anything about it on the net so I thought I'd post it here. This is
related to bug NH-2010 in JIRA, but it doesn't explain how to fix it,
so here goes:
I repeatedly got this error:
System.InvalidCastException: Unable to cast object of type
'System.Boolean' to type 'System.String'.
at NHibernate.Type.AbstractStringType.ToString(Object val) in d:
\CSharp\NH\nhibernate\src\NHibernate\Type\AbstractStringType.cs:line
32
at NHibernate.Type.NullableType.ToLoggableString(Object value,
ISessionFactoryImplementor factory) in d:\CSharp\NH\nhibernate\src
\NHibernate\Type\NullableType.cs:line 109
at NHibernate.Impl.Printer.ToString(IDictionary`2 namedTypedValues)
in d:\CSharp\NH\nhibernate\src\NHibernate\Impl\Printer.cs:line 68
at NHibernate.Cache.QueryKey.ToString() in d:\CSharp\NH\nhibernate
\src\NHibernate\Cache\QueryKey.cs:line 216
at NHibernate.Caches.SysCache2.SysCacheRegion.GetCacheKey(Object
identifier)
It tried to cast a bool to a string (e.g. "something =
(string)theBool"). You can't do that.
The problem was this string:
queryable = queryable.Where(x => x.IsInvoiceToSupplier ==
false);
It's not the "IsInvoiceToSupplier" that's the problem - it's the
"false"! It works when you write it like this:
queryable = queryable.Where(x => !x.IsInvoiceToSupplier);
Also, this:
queryable = queryable.Where(x =>
x.IsInvoiceToSupplier == true);
should be like this:
queryable = queryable.Where(x =>
x.IsInvoiceToSupplier);
You'd think it'd generate the exact same bytecode, but nooo....
So we need to be really careful with what we put in the "Where" clause
on IQueryable:s.
Note that this problem only shows up if you have debug logging enabled
or if you use query caching since the query cache key is generated
from the generated text query.
I suppose this in not technically a bug in NHibernate, but rather how
linq works and the interactions between them, but it was still a hard
bug to track down.
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