C＃a在对象列表中有一个列表。

C# a having a list inside a list of objects. Will not allow .add

我一直在犯这个错误。

An unhandled exception of type 'System.NullReferenceException' occurred in CustomerExcelreader.exe

其他信息：

Object reference not set to an instance of an object.

我不知道为什么，因为我有一个全局对象，而且我知道对象可以工作，因为当我使用对象的非列表值时，一切都可以正常工作。

这是实际存在问题的对象。

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using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace CustomerExcelreader
{
public class customers
{
public customers()
{

}
/// <summary>
/// These work just fine.
/// </summary>
public String Guest { get; set; }
public String Contact { get; set; }
public String ClubNumber { get; set; }//GuestNumber
public String CasioNumber { get; set; }

/// <summary>
/// Lists of lists
/// </summary>
public List<String> Dates { get; set; }
public List<String> Description { get; set; }
public List<Double> moneyIN { get; set; }
public List<Double> moneyOUT { get; set; }
public List<Double> Balance { get; set; }
public List<String> Remarks { get; set; }

}
}

这里是它与任何列表值混淆的地方，但是正常变量是可以的。

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private void addButton_Click(object sender, EventArgs e)
{
//customers add_customerHistory;
if (listNames.SelectedIndex >= 0)// && listNames.SelectedIndex <= Pathlist.Capacity)//somehow SelectedIndex could be less then 0 by not picking something.
{
//add_customerHistory = CustomerHistoryList[listNames.SelectedIndex];
textBox1.Text = CustomerHistoryList[listNames.SelectedIndex].ClubNumber;
CustomerHistoryList[listNames.SelectedIndex].Dates.Add(DateBox.Text);
CustomerHistoryList[listNames.SelectedIndex].Description.Add(DescriptionBox.Text);
CustomerHistoryList[listNames.SelectedIndex].moneyIN.Add(Convert.ToDouble(InBox.Text));
CustomerHistoryList[listNames.SelectedIndex].moneyOUT.Add(Convert.ToDouble(OutBox.Text));
CustomerHistoryList[listNames.SelectedIndex].Balance.Add(Convert.ToDouble(BalanceBox.Text));
CustomerHistoryList[listNames.SelectedIndex].Remarks.Add(RemarkBox.Text);
//CustomerHistoryList[listNames.SelectedIndex].CasioNumber ="Its been changed";
richTextBox1.Text = CustomerHistoryList[listNames.SelectedIndex].CasioNumber;

}
else
{
CustomerHistoryList[0].Dates.Add(DateBox.Text);
CustomerHistoryList[0].Description.Add(DescriptionBox.Text);
CustomerHistoryList[0].moneyIN.Add(Convert.ToDouble(InBox.Text));
CustomerHistoryList[0].moneyOUT.Add(Convert.ToDouble(OutBox.Text));
CustomerHistoryList[0].Balance.Add(Convert.ToDouble(BalanceBox.Text));
CustomerHistoryList[0].Remarks.Add(RemarkBox.Text);
}

}

它在这里不起作用似乎很奇怪。我想这和物体内部的列表有关吧？我听说那些东西会很奇怪。