C＃变量问题

Question

一些C＃变量有问题。 无法弄清楚我在做什么错。 可能有些简单，但是我已经做了一段时间了。

public class DataFileLoad
{
    //Public jagged array variables

    public string[][] aConfJag = null;
    public string[][] aPartJag = null;
    public string[][] aTypeJag = null;
    public string[][] aWkshpJag = null;
    public string[][] aWorkJag = null;

    public void loadFiles()
    {
        //The path of our exectuable
        string exePath = Application.StartupPath;

        //Set our working directory to our exe path for file reading
        Directory.SetCurrentDirectory(exePath);

        string[] aConferences = File.ReadAllLines(@"DATA\CONFERENCES.txt");
        string[] aParticipants = File.ReadAllLines(@"DATA\PARTICIPANTS.txt");
        string[] aType = File.ReadAllLines(@"DATA\TYPE.txt");
        string[] aWkshpReg = File.ReadAllLines(@"DATA\WKSHP_REGISTRATIONS.txt");
        string[] aWorkshops = File.ReadAllLines(@"DATA\WORKSHOPS.txt");

        //Make our arrays jagged for easier processing
        string[][] aConfJag  = aConferences.Select(line => line.Split(',').ToArray()).ToArray();
        string[][] aPartJag  = aParticipants.Select(line => line.Split(',').ToArray()).ToArray();
        string[][] aTypeJag  = aType.Select(line => line.Split(',').ToArray()).ToArray();
        string[][] aWkshpJag = aWkshpReg.Select(line => line.Split(',').ToArray()).ToArray();
        string[][] aWorkJag  = aWorkshops.Select(line => line.Split(',').ToArray()).ToArray();
    }
}

当我尝试从另一个类访问变量时，它们显示为null并引发异常。

public void updateFormData()
{
    //Participant Type
    var data = new DataFileLoad();
    data.loadFiles();
    foreach(string[] e in data.aTypeJag)
    {
        MessageBox.Show(e[1]);
        comboConference.Items.Add(e[1]);
    }
}

 System.NullReferenceException was unhandled HResult=-2147467261 Message=Object reference not set to an instance of an object. Source=FBLA_App 

是我得到的。 有什么想法吗？ 不太确定为什么我会得到空变量。

Answer 1

问题是您正在loadFiles方法中定义新变量。

改为这样做：

public class DataFileLoad
{
    //Public jagged array variables
    public string[][] aConfJag = null;
    public string[][] aPartJag = null;
    public string[][] aTypeJag = null;
    public string[][] aWkshpJag = null;
    public string[][] aWorkJag = null;

    public void loadFiles()
    {
        //The path of our exectuable
        string exePath = Application.StartupPath;

        //Set our working directory to our exe path for file reading
        Directory.SetCurrentDirectory(exePath);

        string[] aConferences = File.ReadAllLines(@"DATA\CONFERENCES.txt");
        string[] aParticipants = File.ReadAllLines(@"DATA\PARTICIPANTS.txt");
        string[] aType = File.ReadAllLines(@"DATA\TYPE.txt");
        string[] aWkshpReg = File.ReadAllLines(@"DATA\WKSHP_REGISTRATIONS.txt");
        string[] aWorkshops = File.ReadAllLines(@"DATA\WORKSHOPS.txt");

        //Make our arrays jagged for easier processing
        aConfJag  = aConferences.Select(line => line.Split(',').ToArray()).ToArray();
        aPartJag  = aParticipants.Select(line => line.Split(',').ToArray()).ToArray();
        aTypeJag  = aType.Select(line => line.Split(',').ToArray()).ToArray();
        aWkshpJag = aWkshpReg.Select(line => line.Split(',').ToArray()).ToArray();
        aWorkJag  = aWorkshops.Select(line => line.Split(',').ToArray()).ToArray();
    }
}

我也强烈建议 ，由于是你不公开这些变量。 而是将它们封装在只读属性中，以便不能从DataFileLoad类外部更改其值。

Answer 2

您通过重新声明来“隐藏”类字段。 只需摘下声明：

    //Make our arrays jagged for easier processing
    aConfJag  = aConferences.Select(line => line.Split(',').ToArray()).ToArray();
    aPartJag  = aParticipants.Select(line => line.Split(',').ToArray()).ToArray();
    aTypeJag  = aType.Select(line => line.Split(',').ToArray()).ToArray();
    aWkshpJag = aWkshpReg.Select(line => line.Split(',').ToArray()).ToArray();
    aWorkJag  = aWorkshops.Select(line => line.Split(',').ToArray()).ToArray();

Answer 3

更改

        string[][] aConfJag  = aConferences.Select(line => line.Split(',').ToArray()).ToArray();
        string[][] aPartJag  = aParticipants.Select(line => line.Split(',').ToArray()).ToArray();
        string[][] aTypeJag  = aType.Select(line => line.Split(',').ToArray()).ToArray();
        string[][] aWkshpJag = aWkshpReg.Select(line => line.Split(',').ToArray()).ToArray();
        string[][] aWorkJag  = aWorkshops.Select(line => line.Split(',').ToArray()).ToArray();

至

       aConfJag  = aConferences.Select(line => line.Split(',').ToArray()).ToArray();
       aPartJag  = aParticipants.Select(line => line.Split(',').ToArray()).ToArray();
       aTypeJag  = aType.Select(line => line.Split(',').ToArray()).ToArray();
       aWkshpJag = aWkshpReg.Select(line => line.Split(',').ToArray()).ToArray();
       aWorkJag  = aWorkshops.Select(line => line.Split(',').ToArray()).ToArray();

您正在创建新变量，而不是将其分配给您的类级变量