问题
this is almost the same as this question except using NH's mapping-by-code.
I really need the virtual properties because i also want to use SchemaExport to create the database for different rdbms without the need to create/maintain scripts for each.
Maybe there is a MbC Guru who knows how to do it with MbC
Update: the obvious simple code
Property("dummyProperty", c =>
{
c.Column("legacyColumn");
c.Access(typeof(MyPropertyAccessor));
});
does not work
NHibernate.MappingException: Unable to instantiate mapping class (see InnerException): Test.MbC.GroupMap ---> System.Reflection.TargetInvocationException: Ein Aufrufziel hat einen Ausnahmefehler verursacht. ---> NHibernate.MappingException: Member not found. The member 'dummyProperty' does not exists in type Test.Data.Group
bei NHibernate.Mapping.ByCode.Impl.CustomizersImpl.PropertyContainerCustomizer`1.GetPropertyOrFieldMatchingNameOrThrow(String memberName)
bei NHibernate.Mapping.ByCode.Impl.CustomizersImpl.PropertyContainerCustomizer`1.RegisterNoVisiblePropertyMapping(String notVisiblePropertyOrFieldName, Action`1 mapping)
bei
...
neither does this, because god knows why MbC checks internally with reflection, that the property does exist on the class.
var parameter = Expression.Parameter(typeof(T), "x");
Expression body = Expression.Property(parameter, new GetterPropertyInfo(typeof(T), defaultgetter));
body = Expression.Convert(body, typeof(object));
var lambda = Expression.Lambda<Func<T, object>>(body, parameter);
Property(lambda, m =>
{
m.Column(defaultgetter.PropertyName);
m.Access(propertyAccessorType);
});
and even disabling the test with reflection through overriding RegisterProperty()
in ClassMapping it still throws while building the hbm complaining:
System.ArgumentOutOfRangeException: Can't add a property of another graph
Parametername: property
bei NHibernate.Mapping.ByCode.Impl.AbstractBasePropertyContainerMapper.Proper
ty(MemberInfo property, Action`1 mapping)
bei NHibernate.Mapping.ByCode.ModelMapper.MapProperty(MemberInfo member, Prop
ertyPath propertyPath, IMinimalPlainPropertyContainerMapper propertiesContainer)
bei NHibernate.Mapping.ByCode.ModelMapper.MapProperties(Type propertiesContai
nerType, IEnumerable`1 propertiesToMap, IPropertyContainerMapper propertiesConta
iner, PropertyPath path)
bei NHibernate.Mapping.ByCode.ModelMapper.MapProperties(Type propertiesContai
nerType, IEnumerable`1 propertiesToMap, IPropertyContainerMapper propertiesConta
iner)
bei NHibernate.Mapping.ByCode.ModelMapper.MapRootClass(Type type, HbmMapping
mapping)
bei NHibernate.Mapping.ByCode.ModelMapper.CompileMappingFor(IEnumerable`1 typ
es)
Mapping by code should be more flexible than FNH? Where?
回答1:
After investing a lot of time trying to do this rather simple mapping in MbC i concede and throw aboard MbC again.
Even simple Mapping like this is not remotely possible with the oh so flexible MbC
public class MyClassMap : ClassMap<MyClass>
{
public MyClassMap()
{
Map(x => this.VirtualProp, "legacyColumn").Default("123").Access.None();
}
public long VirtualProp { get; set; }
}
the advantage here is that i can use SchemaExport to create a compatible schema for the legacy app without polluting my domain classes
回答2:
You can do it pretty much in the same way as in the linked question. Implementation of PropertyAccessor
stays the same. To use it within mapping-by-code, map the column using string overload (the name of the property is required but not really used in this case) and attach the accessor:
Property("dummyPropertyNameForConstant", c =>
{
c.Column("ConstantColumn");
c.Access(typeof(CustomAccessor));
});
来源:https://stackoverflow.com/questions/10482864/database-column-to-constant-value-without-the-need-for-a-property-in-the-entity