C# 使用抛出捕获OOWPF进行简单修复

形势

我正在开发一个OO WPF应用程序，该应用程序允许不同类型的成员加入竞赛，但我遇到了一个try-catch问题

问题

用外行的话来说，我的问题是，我试图让一名会员加入一场具有以下代码的比赛：

race.joinJunior((JuniorMember)hillracing.searchMembers(Username));

因此，JuniorMember（谁的对象是通过searchMember方法和预先存在的用户名参数找到的）将通过joinJunior方法作为初级成员加入比赛

这段代码本身不是问题所在，但它确实导致了问题，因为它调用了joinJunior方法，而我的问题就在这里

public override void joinJunior(JuniorMember jm)
        {
            if (junior != null)
            {
                //Increment the current members on the race by 1.
                currentRunners++;

                if (currentRunners > limitRace)
                {

                    currentRunners = limitRace;

                    throw new Exception(junior.FirstName + " would be this races: " + limitRace + 1 + "th runner. This race can only take: " + limitRace);


                }
            }
            //if the members type doesnt equal the member join permission then they shouldn't be able to join.
            else if (junior.memType != permRace)
            {
                //throws an exception if the member doesn't have the correct type junior
                throw new Exception(senior.FirstName + " does not meet the requirements to join this race, must be type: " + permRace);
            }
            //if the members gender isn't equal to the races gender requirement they shouldn't be able to join that race.
            else if (junior.gender != genRace)
            {
                //throws an exception if the member doesn't have the correct gender type.
                throw new Exception(junior.FirstName + " does not meet the requirements to join this race, must be a: " + genRace);
            }

            else
            {
                //if all other conditions are met, and the member meets requirements, let the member join the race and add a return date of 21 days.
                junior = jm;

                returnDate = DateTime.Today.AddDays(21);
            }
        }

所以，这条线出现的问题就是这个问题

else if (junior.memType != permRace)
            {
                //throws an exception if the member doesn't have the correct type junior
                throw new Exception(senior.FirstName + " does not meet the requirements to join this race, must be type: " + permRace);
            }

当抛出错误时，它会给出一个异常消息“Object reference not set to a instance of a Object”，而不是我要求它抛出的异常。你看，我希望它抛出这个异常，它这样做是正确的，但它没有提供正确的消息

---

我做错了什么？

始终检查主设备和辅助设备是否存在空情况，例如

if ((junior == null) || (junior.memType == null))

---

然后根据

junior

verses

junior处理错误情况。对于
memType
而言，memType

可能是一个真正的调试/开发错误，而已知的缺失

junior

senior可能为空，与引发异常无关，您正在尝试对不存在的对象调用FirstName。我猜应该是

junior。FirstName

，而不是senior。哇，我甚至没有注意到那个senior，直到你说出来，我一定跳过了它，认为它是更伟大的东西，把这个作为一个答案，我不敢相信我这么愚蠢。而且，我相信你的

joinJunior

方法中的块是不正确的。第一个（

if（junior！=null）

）应该涵盖更多的情况，因为您正在执行

junior.memType！=permRace

在else if中-如果您到达那里，则可以保证

junior

为

null

（因此，NullReferenceException）