如何检查列表类是否为空 [英] How to check whether list class is empty or not

问题描述

我需要检查列表类是否为空



我是使用以下内容

Hi,

I need to check whether list class is empty or not

I am using following for that

private CANBusDetails msgDetailsOfBus(CANBusDetails busDetails)
        {
            if (busDetails.Schedulability > 0)
                busDetails.Alpha = 0;

            busDetails.CANMessageDetailsList.Clear();
            foreach (CANMessageDetails Details in busDetails.OutputExcelMessageDetailsList)
            {
                CANMessageDetails tempMsgDetails = new CANMessageDetails();

                tempMsgDetails.MessageName = Details.MessageName;
                tempMsgDetails.HexMessageId = Details.HexMessageId;
                tempMsgDetails.TxNode = Details.TxNode;
                tempMsgDetails.CycleTime = Details.CycleTime;
                tempMsgDetails.CycleType = Details.CycleType;
                tempMsgDetails.Deadline = Details.Deadline;
                tempMsgDetails.Priority = Details.Priority;
                tempMsgDetails.Utilization = Details.Utilization;
                tempMsgDetails.BlockingTime = Details.BlockingTime;
                tempMsgDetails.BusyPeriod = Details.BusyPeriod;
                tempMsgDetails.WaitingTime = Details.WaitingTime;
                tempMsgDetails.NumberOfInvocations = Details.NumberOfInvocations;
                tempMsgDetails.WorstCaseInvocation = Details.WorstCaseInvocation;
                tempMsgDetails.WorstCaseResponseTime = Details.WorstCaseResponseTime;
                tempMsgDetails.ResponseTimeList.AddRange(Details.ResponseTimeList);
                tempMsgDetails.LatencyList.AddRange(Details.LatencyList);

                busDetails.CANMessageDetailsList.Add(tempMsgDetails);


            }
            return busDetails;

        }


           if (msgDetailsOfBus(SCANLA.Run.BusDetails[0]) == null)
                
                    NoValidBuses++;

                if (msgDetailsOfBus(SCANLA.Run.BusDetails[1]) == null)
               
                    NoValidBuses++;
                if (msgDetailsOfBus(SCANLA.Run.BusDetails[2]) == null)
               
                    NoValidBuses++;
                if (msgDetailsOfBus(SCANLA.Run.BusDetails[3]) == null)
                
                    NoValidBuses++

;



但是当列表class是空的，程序没有递增NoValidBuses

它显示了一些异常



如何解决这个问题？





谢谢

John

;

But when the list class is empty, the program is not incrementing NoValidBuses
It is showing some exception

How to solve this problem???


Thanks
John

推荐答案

来自看起来，该函数永远不会返回null，因为它只返回输入'bus details'类。如果输入为null，它将抛出异常。



如何做到以下其中一项：

From the looks of it, that function will never return null, as it simply returns the input 'bus details' class .. It will throw an exception if the input is null.

How about one of the following:

private bool msgDetailsOfBus(CANBusDetails busDetails)
{
    int count = 0;  // possible solution #2

    if (busDetails.Schedulability > 0)
        busDetails.Alpha = 0;
 
    busDetails.CANMessageDetailsList.Clear();

    // Possible solution #1... short-circuit return
    if (busDetails.OutputExcelMessageDetailsList.Count <= 0)
        return false;

    foreach (CANMessageDetails Details in busDetails.OutputExcelMessageDetailsList)
    {
       CANMessageDetails tempMsgDetails = new CANMessageDetails();
 
       tempMsgDetails.MessageName = Details.MessageName;
       tempMsgDetails.HexMessageId = Details.HexMessageId;
       tempMsgDetails.TxNode = Details.TxNode;
       tempMsgDetails.CycleTime = Details.CycleTime;
       tempMsgDetails.CycleType = Details.CycleType;
       tempMsgDetails.Deadline = Details.Deadline;
       tempMsgDetails.Priority = Details.Priority;
       tempMsgDetails.Utilization = Details.Utilization;
       tempMsgDetails.BlockingTime = Details.BlockingTime;
       tempMsgDetails.BusyPeriod = Details.BusyPeriod;
       tempMsgDetails.WaitingTime = Details.WaitingTime;
       tempMsgDetails.NumberOfInvocations = Details.NumberOfInvocations;
       tempMsgDetails.WorstCaseInvocation = Details.WorstCaseInvocation;
       tempMsgDetails.WorstCaseResponseTime = Details.WorstCaseResponseTime;
       tempMsgDetails.ResponseTimeList.AddRange(Details.ResponseTimeList);
       tempMsgDetails.LatencyList.AddRange(Details.LatencyList);
 
       busDetails.CANMessageDetailsList.Add(tempMsgDetails);

       count++;
    }
            
    return true;    // possible solution #1

    if (count > 0)
        return true;  // possible solution #2
}
 

if (msgDetailsOfBus(SCANLA.Run.BusDetails[0]) == false)
    NoValidBuses++;
 
if (msgDetailsOfBus(SCANLA.Run.BusDetails[1]) == false)
    NoValidBuses++;

if (msgDetailsOfBus(SCANLA.Run.BusDetails[2]) == false)               
    NoValidBuses++;

if (msgDetailsOfBus(SCANLA.Run.BusDetails[3]) == false)                
    NoValidBuses++

我假设CANMessageDetailsList是列表< T> 类型，所以

I'm assuming that CANMessageDetailsList is List<T> type, so

if(CANMessageDetailsList.Count > 0)
{
    // list is not empty..
}

正确我，如果我的假设是错的，否则它应该有效。



-KR

Correct me, if my assumption is wrong, otherwise it should work.

-KR

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