Nhibernate，需要帮助来修复我的选择查询

Question

我是休眠新手。我正在使用的是nhibernate 3。这是我需要做的，选择ID为1的用户。如果该用户不存在，则返回null。

var selectedUser = session.Query().Where(u=>u.Id == 1).FirstOrDefault();

                if (selectedUser == null)
                {
                    userID = (int)session.Save(user);
                }

我的选择查询没有。

这是我收到的错误消息。

could not execute query\r\n[ select TOP (@p0) user0_.Id as Id0_, user0_.Username as Username0_, user0_.Password as Password0_, user0_.CreateDate as CreateDate0_, user0_.Avatar as Avatar0_, user0_.AccountTypeId as AccountT6_0_, user0_.FirstName as FirstName0_, user0_.LastName as LastName0_, user0_.MiddleName as MiddleName0_, user0_.Email as Email0_, user0_.OtherId as OtherId0_ from [User] user0_ where user0_.Id=@p1 ]\r\n  Name:p1 - Value:1\r\n[SQL: select TOP (@p0) user0_.Id as Id0_, user0_.Username as Username0_, user0_.Password as Password0_, user0_.CreateDate as CreateDate0_, user0_.Avatar as Avatar0_, user0_.AccountTypeId as AccountT6_0_, user0_.FirstName as FirstName0_, user0_.LastName as LastName0_, user0_.MiddleName as MiddleName0_, user0_.Email as Email0_, user0_.OtherId as OtherId0_ from [User] user0_ where user0_.Id=@p1]"}
 [NHibernate.Exceptions.GenericADOException]: {"could not execute query\r\n[ select TOP (@p0) user0_.Id as Id0_, user0_.Username as Username0_, user0_.Password as Password0_, user0_.CreateDate as CreateDate0_, user0_.Avatar as Avatar0_, user0_.AccountTypeId as AccountT6_0_, user0_.FirstName as FirstName0_, user0_.LastName as LastName0_, user0_.MiddleName as MiddleName0_, user0_.Email as Email0_, user0_.OtherId as OtherId0_ from [User] user0_ where user0_.Id=@p1 ]\r\n  Name:p1 - Value:1\r\n[SQL: select TOP (@p0) user0_.Id as Id0_, user0_.Username as Username0_, user0_.Password as Password0_, user0_.CreateDate as CreateDate0_, user0_.Avatar as Avatar0_, user0_.AccountTypeId as AccountT6_0_, user0_.FirstName as FirstName0_, user0_.LastName as LastName0_, user0_.MiddleName as MiddleName0_, user0_.Email as Email0_, user0_.OtherId as OtherId0_ from [User] user0_ where user0_.Id=@p1]"}
Data: {System.Collections.ListDictionaryInternal}
HelpLink: null
InnerException: {"Invalid object name 'User'."}
Message: "could not execute query\r\n[ select TOP (@p0) user0_.Id as Id0_, user0_.Username as Username0_, user0_.Password as Password0_, user0_.CreateDate as CreateDate0_, user0_.Avatar as Avatar0_, user0_.AccountTypeId as AccountT6_0_, user0_.FirstName as FirstName0_, user0_.LastName as LastName0_, user0_.MiddleName as MiddleName0_, user0_.Email as Email0_, user0_.OtherId as OtherId0_ from [User] user0_ where user0_.Id=@p1 ]\r\n  Name:p1 - Value:1\r\n[SQL: select TOP (@p0) user0_.Id as Id0_, user0_.Username as Username0_, user0_.Password as Password0_, user0_.CreateDate as CreateDate0_, user0_.Avatar as Avatar0_, user0_.AccountTypeId as AccountT6_0_, user0_.FirstName as FirstName0_, user0_.LastName as LastName0_, user0_.MiddleName as MiddleName0_, user0_.Email as Email0_, user0_.OtherId as OtherId0_ from [User] user0_ where user0_.Id=@p1]"
Source: "NHibernate"
StackTrace: "   at NHibernate.Loader.Loader.DoList(ISessionImplementor session,    QueryParameters queryParameters)\r\n   at NHibernate.Loader.Loader.ListIgnoreQueryCache(ISessionImplementor session, QueryParameters queryParameters)\r\n   at NHibernate.Loader.Loader.List(ISessionImplementor session, QueryParameters queryParameters, ISet`1 querySpaces, IType[] resultTypes)\r\n   at NHibernate.Hql.Ast.ANTLR.Loader.QueryLoader.List(ISessionImplementor session, QueryParameters queryParameters)\r\n   at NHibernate.Hql.Ast.ANTLR.QueryTranslatorImpl.List(ISessionImplementor session, QueryParameters queryParameters)\r\n   at NHibernate.Engine.Query.HQLQueryPlan.PerformList(QueryParameters queryParameters, ISessionImplementor session, IList results)\r\n   at NHibernate.Impl.SessionImpl.List(IQueryExpression queryExpression, QueryParameters queryParameters, IList results)\r\n   at NHibernate.Impl.AbstractSessionImpl.List(IQueryExpression queryExpression, QueryParameters parameters)\r\n   at NHibernate.Impl.ExpressionQu

eryImpl.List()\r\n 在 NHibernate.Linq.NhQueryProvider.ExecuteQuery(NhLinqExpression nhLinqExpression, IQuery 查询, NhLinqExpression nhQuery)\r\n 在 NHibernate.Linq.NhQueryProvider.Execute(表达式表达式)\r\n 在 NHibernate。 Linq.NhQueryProvider.Execute[TResult](表达式表达式）\r\n 位于 System.Linq.Queryable.FirstOrDefault[TSource](IQueryable`1 源)\r\n 位于 C:\code\net 中的 DevelopmentStack.Domain.Repositories.Concrete.NUserRepository.AddUser(User user) \DevelopmentStack\DevelopmentStack.Domain\Repositories\Concrete\NUserRepository.cs：第 30 行” TargetSite：{System.Collections.IList DoList（NHibernate.Engine.ISessionImplementor，NHibernate.Engine.QueryParameters）} >

Answer 1

这可能是因为 User 是保留关键字。如果您在 hbm 中映射它，请确保您在表名称中提供了转义符：`User（用户应该被 `` 由于 markdown 而无法正确写入）或 [User] 包围。两者的区别在于，第二个不关心方言。

Answer 2

尝试：

var selectedUser = session.Get<User>(1);

通过 ID 检索实体时，您应该始终使用 Get 而不是查询。如果实体不存在，则返回 null。