在NHibernate的QueryOver GUID比较引发错误

Question

我想要获取所有Product其中CheckedOutToGuid为空或是当前用户的Guid。我曾尝试使用以下QueryOver：

public IEnumerable<IProduct> GetProducts(IUser user, Expression<Func<IProduct, bool>> predicate) 
    { 
     return Context.GetSession().QueryOver<Product>() 
      .Where(x => (x.CheckedOutByGuid == null) || Guid.Equals(user.UserGuid, x.CheckedOutByGuid) 
      .OrderBy(x => x.Version).Desc 
      .OrderBy(x => x.DisplayName).Asc.List(); 
    } 

，但我得到一个错误：

Atf.NUnit.Model.TestDatabase.TestModule1(): 
System.Exception : Unrecognised method call: System.Object:Boolean Equals(System.Object, System.Object) 

什么是这个错误的原因是什么？我尝试删除(x.CheckedOutByGuid == null)，以便不需要OR，但仍然会得到相同的错误。

UPDATE

由于@Andrew Whitaker sugggested，我改变了一行

.Where(x => (x.CheckedOutByGuid == null) || (user.UserGuid == x.CheckedOutByGuid)) 

现在，这将导致以下异常：

Atf.NUnit.Model.TestDatabase.TestModule1(): 
NHibernate.QueryException : could not resolve property: user of: Atf.Model.Internal.Product 
bei NHibernate.Persister.Entity.AbstractPropertyMapping.ToType(String propertyName) in p:\nhibernate-core\src\NHibernate\Persister\Entity\AbstractPropertyMapping.cs:Zeile 37. 
bei NHibernate.Persister.Entity.AbstractEntityPersister.GetSubclassPropertyTableNumber(String propertyPath) in p:\nhibernate-core\src\NHibernate\Persister\Entity\AbstractEntityPersister.cs:Zeile 1776. 
bei NHibernate.Persister.Entity.BasicEntityPropertyMapping.ToColumns(String alias, String propertyName) in p:\nhibernate-core\src\NHibernate\Persister\Entity\BasicEntityPropertyMapping.cs:Zeile 31. 
bei NHibernate.Persister.Entity.AbstractEntityPersister.ToColumns(String alias, String propertyName) in p:\nhibernate-core\src\NHibernate\Persister\Entity\AbstractEntityPersister.cs:Zeile 1742. 
bei NHibernate.Loader.Criteria.CriteriaQueryTranslator.GetColumns(ICriteria subcriteria, String propertyName) in p:\nhibernate-core\src\NHibernate\Loader\Criteria\CriteriaQueryTranslator.cs:Zeile 590. 
bei NHibernate.Loader.Criteria.CriteriaQueryTranslator.GetColumnsUsingProjection(ICriteria subcriteria, String propertyName) in p:\nhibernate-core\src\NHibernate\Loader\Criteria\CriteriaQueryTranslator.cs:Zeile 561. 
bei NHibernate.Criterion.CriterionUtil.GetColumnNamesUsingPropertyName(ICriteriaQuery criteriaQuery, ICriteria criteria, String propertyName) in p:\nhibernate-core\src\NHibernate\Criterion\CriterionUtil.cs:Zeile 64. 
bei NHibernate.Criterion.CriterionUtil.GetColumnNames(String propertyName, IProjection projection, ICriteriaQuery criteriaQuery, ICriteria criteria, IDictionary`2 enabledFilters) in p:\nhibernate-core\src\NHibernate\Criterion\CriterionUtil.cs:Zeile 20. 
bei NHibernate.Criterion.PropertyExpression.ToSqlString(ICriteria criteria, ICriteriaQuery criteriaQuery, IDictionary`2 enabledFilters) in p:\nhibernate-core\src\NHibernate\Criterion\PropertyExpression.cs:Zeile 74. 
bei NHibernate.Criterion.LogicalExpression.ToSqlString(ICriteria criteria, ICriteriaQuery criteriaQuery, IDictionary`2 enabledFilters) in p:\nhibernate-core\src\NHibernate\Criterion\LogicalExpression.cs:Zeile 77. 
bei NHibernate.Loader.Criteria.CriteriaQueryTranslator.GetWhereCondition(IDictionary`2 enabledFilters) in p:\nhibernate-core\src\NHibernate\Loader\Criteria\CriteriaQueryTranslator.cs:Zeile 202. 
bei NHibernate.Loader.Criteria.CriteriaJoinWalker..ctor(IOuterJoinLoadable persister, CriteriaQueryTranslator translator, ISessionFactoryImplementor factory, ICriteria criteria, String rootEntityName, IDictionary`2 enabledFilters) in p:\nhibernate-core\src\NHibernate\Loader\Criteria\CriteriaJoinWalker.cs:Zeile 58. 
bei NHibernate.Loader.Criteria.CriteriaLoader..ctor(IOuterJoinLoadable persister, ISessionFactoryImplementor factory, CriteriaImpl rootCriteria, String rootEntityName, IDictionary`2 enabledFilters) in p:\nhibernate-core\src\NHibernate\Loader\Criteria\CriteriaLoader.cs:Zeile 41. 
bei NHibernate.Impl.SessionImpl.List(CriteriaImpl criteria, IList results) in p:\nhibernate-core\src\NHibernate\Impl\SessionImpl.cs:Zeile 1948. 
bei NHibernate.Impl.CriteriaImpl.List(IList results) in p:\nhibernate-core\src\NHibernate\Impl\CriteriaImpl.cs:Zeile 265. 
bei NHibernate.Impl.CriteriaImpl.List[T]() in p:\nhibernate-core\src\NHibernate\Impl\CriteriaImpl.cs:Zeile 276. 
bei NHibernate.Criterion.QueryOver`1.List() in p:\nhibernate-core\src\NHibernate\Criterion\QueryOver.cs:Zeile 67. 
bei NHibernate.Criterion.QueryOver`1.NHibernate.IQueryOver<TRoot>.List() in p:\nhibernate-core\src\NHibernate\Criterion\QueryOver.cs:Zeile 214. 
bei Atf.Model.Database.DatabasePersistence.GetProducts(IUser user, Expression`1 predicate) in D:\my_workspaces\visualstudioprojects\MyTestFramework\Atf.Model\Database\DatabasePersistence.cs:Zeile 247. 
bei Atf.NUnit.Model.TestDatabase.TestModule1() in D:\my_workspaces\visualstudioprojects\MyTestFramework\Atf.zNUnit.Model\TestDatabase.cs:Zeile 59. 

嘛，然后我尝试这样做：

public IEnumerable<IProduct> GetProducts(IUser user, Expression<Func<IProduct, bool>> predicate) 
    { 
     Guid g = user.UserGuid; 
     return Context.GetSession().QueryOver<Product>() 
      .Where(x => (x.CheckedOutByGuid == null) || (g == x.CheckedOutByGuid)) 
      .OrderBy(x => x.Version).Desc 
      .OrderBy(x => x.DisplayName_DE).Asc.List(); 
    } 

这是当我发现user为空:-(这是错误的原因。错误信息导致我的方向错误。

Answer 1

NHibernate试图将Guid.Equals转换为SQL表达式。 NHibernate不会将Guid.Equals识别为可以变成SQL的东西，因此是例外。

如果把上面一行写着：

.Where(x => (x.CheckedOutByGuid == null) || user.UserGuid == x.CheckedOutByGuid) 

一切都应该很好地工作。