C#（对象数组）对象引用未设置为对象的实例
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C# (Array of object) object reference not set to an instance of an object
提问by Beginner
I am getting the object reference error in this line: emp[count].emp_id = int.Parse(parts[0]);
我在这一行收到对象引用错误： emp[count].emp_id = int.Parse(parts[0]);
in this code
在这段代码中
this program to read from file and store in array of object
这个程序从文件中读取并存储在对象数组中
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
public class employees
{
public int emp_id;
public string firstName;
public string lastName;
public double balance;
}
private void btnOpen_Click(object sender, EventArgs e)
{
OpenFileDialog file = new OpenFileDialog();
DialogResult result = file.ShowDialog();
if (result == DialogResult.Cancel) return;
string fileName = file.FileName;
StreamReader reader = new StreamReader(fileName);
string[] lines = File.ReadAllLines(fileName);
int emp_count = lines.Count<string>();
employees[] emp = new employees[emp_count];
int count = 0;
foreach (string line in lines)
{
string[] parts = new string[4];
parts = line.Split(',');
**emp[count].emp_id = int.Parse(parts[0]);**
emp[count].firstName = parts[1];
emp[count].lastName = parts[2];
emp[count].balance = double.Parse(parts[3]);
count++;
txtGet.Text += emp[count].emp_id + " " + emp[count].firstName + " " + emp[count].lastName + " " + emp[count].balance + " \n ";
}
采纳答案by DaveShaw
You need to initialise emp[count]to something.
你需要初始化emp[count]一些东西。
You can do this by adding the following:
您可以通过添加以下内容来做到这一点：
foreach (string line in lines)
{
emp[count] = new employees();
string[] parts = new string[4];
//....
}
When you call employees[] emp = new employees[emp_count];you initilise empto an array of employeeswith the length of emp_count.
当您调用employees[] emp = new employees[emp_count];initiliseemp到一个employees长度为emp_count.
emp[0] = null;
emp[1] = null;
//etc.
Each element inside empalso needs to be instantiated before you can use it.
里面的每个元素emp也需要先实例化才能使用。
回答by Diego
emp[0]has not been initialized. Class employeesis a nullable type, which means arrays made of it are initialized to nulls. Initialize emp[count]to new employees.
emp[0]尚未初始化。Classemployees是可空类型，这意味着由它组成的数组被初始化为空值。初始化emp[count]为new employees.
BTW, "employees" is a strange name for a class that holds a single employee. I think it should be called Employee, then it makes sens to declare your array like this:
顺便说一句，“ employees”对于一个包含单个员工的类来说是一个奇怪的名字。我认为它应该被调用Employee，然后像这样声明你的数组是有意义的：
`Employee[] employees = new Employee[emp_count];`
