在 linq 查询中返回 null

Question

I fill the data from xml in the model

Some xml tables don't have this(RequestedDeliveryDate,EarliestDeliveryDate,LatestDeliveryDate ) property

For this reason return "Object reference not set to an instance of an object

Help me !!

SchedulingConditions = _detailInformation.Descendants("SchedulingConditions").Select(_schedulingConditions => new SchedulingConditionsModel
{
    SchedulingConditionList = _schedulingConditions.Descendants("SchedulingCondition").Select(_schedulingCondition => new SchedulingCondition
    {
        QuantityToBeDelivered = _schedulingCondition.Element("QuantityToBeDelivered").Value,
        DeliveryPlan = _schedulingCondition.Element("DeliveryPlan").Value,
        Frequency = _schedulingCondition.Element("Frequency").Value,
        RequestedDeliveryDate = _schedulingCondition.Element("RequestedDeliveryDate").Value, --> This property is return null
        EarliestDeliveryDate =  _schedulingCondition.Element("EarliestDeliveryDate").Value, --> This property is return null
        LatestDeliveryDate = _schedulingCondition.Element("LatestDeliveryDate").Value  --> This property is return null 
    }).ToList(),
}).FirstOrDefault(),

Answer 1

You can check if the property is null before trying to get value with "?". If the property is null, the return is null, if it is not null, the return is the property value.

SchedulingConditions = _detailInformation.Descendants("SchedulingConditions").Select(_schedulingConditions => new SchedulingConditionsModel
                            {

                                SchedulingConditionList = _schedulingConditions.Descendants("SchedulingCondition").Select(_schedulingCondition => new SchedulingCondition
                                {

                                    QuantityToBeDelivered = _schedulingCondition.Element("QuantityToBeDelivered").Value,
                                    DeliveryPlan = _schedulingCondition.Element("DeliveryPlan").Value,
                                    Frequency = _schedulingCondition.Element("Frequency").Value,
                                    RequestedDeliveryDate = _schedulingCondition.Element("RequestedDeliveryDate")?.Value, --> This property is return null
                                    EarliestDeliveryDate =  _schedulingCondition.Element("EarliestDeliveryDate")?.Value, --> This property is return null
                                    LatestDeliveryDate = _schedulingCondition.Element("LatestDeliveryDate")?.Value  --> This property is return null 

                                }).ToList(),

                            }).FirstOrDefault(),