Question

我正在尝试使用linq谓词生成过滤器代码。当我使用带有对象的谓词时！= null：

public static Expression<Func<ContactPermitsSearch, bool>> PermitNumberNotNull()
    {
        Expression<Func<ContactPermitsSearch, bool>> predicate = contactPermit => contactPermit.PermitNumber != null;
        return predicate;
    }

由以下人员调用：

public static IQueryable<ContactPermitsSearch> FilterByNameMailingPermit(this IQueryable<ContactPermitsSearch> queryable, string search, bool filterOn)
    {
        var predicate = PredicateBuilder.True<ContactPermitsSearch>();

        predicate = predicate.And(PermitNumberNotNull());

        var filtered = queryable.AsExpandable().Where(predicate);
        return filtered;
    }

生成的SQL语句不包含PermitNumberNotNull谓词语句。

关于解决这个问题的想法？

Answer 1

代码没有明显的错误。我确定如果在将predicate与PermitNumberNotNull()合并之后检查调试器中的contactPermit.PermitNumber，您将看到非空谓词是表达式树的一部分。

唯一合理的假设是EF知道class SimSpout(storm.Spout): # Not much to do here for such a basic spout def initialize(self, conf, context): ## Open the file with read only permit self.f = open('data.txt', 'r') ## Read the first line self._conf = conf self._context = context self._offset = 0 storm.logInfo("Spout instance starting...") # Process the next tuple def nextTuple(self): # check if it reach at the EOF to close it with open(self.f) as f: f.readlines()[self._offset] #Emit a random sentence storm.logInfo("Emiting %s" % line) storm.emit([line]) self._offset = self._offset + 1无法成为null，因为它的必需属性。因此，它只是忽略谓词。

C＃Linq谓词生成从列表中删除所有空值

1 个答案: