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linq2sql查询异常

linq-to-sql linq

Hadi Eskandari · 技术社区 · 16 年前

我正在使用linq2sql运行一个查询,该查询归结为以下查询:



DateTime? expiration = GetExpirationDate();
IQueryable<Persons> persons = GetPersons();
IQueryable<Items> subquery = from i in db.Items
                             where i.ExpirationDate >= expiration
                             select i;

return persons.Where(p => p.Items != null && p.Items.Any(item => subquery.Contains(item)));

当我评估函数的结果时,我得到一个nullreferenceexception,这里是堆栈跟踪。知道我做错了什么吗?!

基本上我想选择所有的人,并按项目到期日期过滤他们。

   at System.Data.Linq.SqlClient.SqlFactory.Member(SqlExpression expr, MemberInfo member)
   at System.Data.Linq.SqlClient.QueryConverter.VisitMemberAccess(MemberExpression ma)
   at System.Data.Linq.SqlClient.QueryConverter.VisitInner(Expression node)
   at System.Data.Linq.SqlClient.QueryConverter.Visit(Expression node)
   at System.Data.Linq.SqlClient.QueryConverter.VisitExpression(Expression exp)
   at System.Data.Linq.SqlClient.QueryConverter.VisitBinary(BinaryExpression b)
   at System.Data.Linq.SqlClient.QueryConverter.VisitInner(Expression node)
   at System.Data.Linq.SqlClient.QueryConverter.Visit(Expression node)
   at System.Data.Linq.SqlClient.QueryConverter.VisitExpression(Expression exp)
   at System.Data.Linq.SqlClient.QueryConverter.VisitBinary(BinaryExpression b)
   at System.Data.Linq.SqlClient.QueryConverter.VisitInner(Expression node)
   at System.Data.Linq.SqlClient.QueryConverter.Visit(Expression node)
   at System.Data.Linq.SqlClient.QueryConverter.VisitExpression(Expression exp)
   at System.Data.Linq.SqlClient.QueryConverter.VisitWhere(Expression sequence, LambdaExpression predicate)
   at System.Data.Linq.SqlClient.QueryConverter.VisitSequenceOperatorCall(MethodCallExpression mc)
   at System.Data.Linq.SqlClient.QueryConverter.VisitMethodCall(MethodCallExpression mc)
   at System.Data.Linq.SqlClient.QueryConverter.VisitInner(Expression node)
   at System.Data.Linq.SqlClient.QueryConverter.Visit(Expression node)
   at System.Data.Linq.SqlClient.QueryConverter.VisitContains(Expression sequence, Expression value)
   at System.Data.Linq.SqlClient.QueryConverter.VisitSequenceOperatorCall(MethodCallExpression mc)
   at System.Data.Linq.SqlClient.QueryConverter.VisitMethodCall(MethodCallExpression mc)
   at System.Data.Linq.SqlClient.QueryConverter.VisitInner(Expression node)
   at System.Data.Linq.SqlClient.QueryConverter.Visit(Expression node)
   at System.Data.Linq.SqlClient.QueryConverter.VisitExpression(Expression exp)
   at System.Data.Linq.SqlClient.QueryConverter.VisitQuantifier(SqlSelect select, LambdaExpression lambda, Boolean isAny)
   at System.Data.Linq.SqlClient.QueryConverter.VisitSequenceOperatorCall(MethodCallExpression mc)
   at System.Data.Linq.SqlClient.QueryConverter.VisitMethodCall(MethodCallExpression mc)
   at System.Data.Linq.SqlClient.QueryConverter.VisitInner(Expression node)
   at System.Data.Linq.SqlClient.QueryConverter.Visit(Expression node)
   at System.Data.Linq.SqlClient.QueryConverter.VisitExpression(Expression exp)
   at System.Data.Linq.SqlClient.QueryConverter.VisitBinary(BinaryExpression b)
   at System.Data.Linq.SqlClient.QueryConverter.VisitInner(Expression node)
   at System.Data.Linq.SqlClient.QueryConverter.Visit(Expression node)
   at System.Data.Linq.SqlClient.QueryConverter.VisitExpression(Expression exp)
   at System.Data.Linq.SqlClient.QueryConverter.VisitWhere(Expression sequence, LambdaExpression predicate)
   at System.Data.Linq.SqlClient.QueryConverter.VisitSequenceOperatorCall(MethodCallExpression mc)
   at System.Data.Linq.SqlClient.QueryConverter.VisitMethodCall(MethodCallExpression mc)
   at System.Data.Linq.SqlClient.QueryConverter.VisitInner(Expression node)
   at System.Data.Linq.SqlClient.QueryConverter.ConvertOuter(Expression node)
   at System.Data.Linq.SqlClient.SqlProvider.BuildQuery(Expression query, SqlNodeAnnotations annotations)
   at System.Data.Linq.SqlClient.SqlProvider.System.Data.Linq.Provider.IProvider.Execute(Expression query)
   at System.Data.Linq.DataQuery`1.System.Collections.Generic.IEnumerable.GetEnumerator()
   at System.Linq.SystemCore_EnumerableDebugView`1.get_Items()

2 回复 | 直到 15 年前

Amy B 16 年前

如果expiration为空,则它仍然不是空引用(提示:reference)。

哈迪,问题是你写的代码很聪明。而是编写可调试的代码。

Keltex 16 年前

是 expiration 无效的?可能有问题。