Form2的personalDetail因保护级别无法访问，跨窗体传值问题排查

编写了一个包含Employee类和两个窗体的程序，尝试从Form1向Form2传递数据时，出现错误：'form 2.personal details' is inaccessible due to its protection level。Employee类及其属性均为public。

相关代码 #

Employee类代码 #

class Employee
{
    public int EmployeeID { get; set; }
    public string Name { get; set; }
    public int Age { get; set; }
}

Form1.cs代码 #

public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
    }

    Employee personalDetail = new Employee();

    private void btnSetValue_Click(object sender, EventArgs e)
    {
        personalDetail.EmployeeID = Convert.ToInt32(txtEmployeeID.Text);
        personalDetail.Name = txtName.Text;
        personalDetail.Age = Convert.ToInt32(txtAge.Text);

        MessageBox.Show("All data received");
    }

    private void btnSend_Click(object sender, EventArgs e)
    {
        personalDetail.EmployeeID = Convert.ToInt32(txtEmployeeID.Text);
        personalDetail.Name = txtName.Text;
        personalDetail.Age= Convert.ToInt32(txtAge.Text);

        Form2 frm = new Form2();
        frm.personalDetail = personalDetail;

        frm.ShowDialog();
    }
}

Form2.cs代码 #

public partial class Form2 : Form
{
    public Form2()
    {
        InitializeComponent();
    }

    Employee personalDetail = new Employee();
  
    private void Form2_Load(object sender, EventArgs e)
    {
        textBox1.Text = personalDetail.EmployeeID.ToString();
        textBox2.Text = personalDetail.Name;
        textBox3.Text = personalDetail.Age.ToString();
    }
}

错误原因 #

Form2中的personalDetail字段未指定访问修饰符，C#中类的字段默认是private级别，外部类（比如Form1）无法直接访问私有成员，这就是报错的核心原因。

解决方案 #

方法一：将Form2的字段改为public #

直接修改Form2的字段访问级别，让Form1可以直接赋值：

public partial class Form2 : Form
{
    public Form2()
    {
        InitializeComponent();
    }

    // 添加public修饰符，开放访问权限
    public Employee personalDetail = new Employee();
  
    private void Form2_Load(object sender, EventArgs e)
    {
        textBox1.Text = personalDetail.EmployeeID.ToString();
        textBox2.Text = personalDetail.Name;
        textBox3.Text = personalDetail.Age.ToString();
    }
}

方法二：通过构造函数传递数据（更推荐） #

这种方式符合面向对象的封装原则，避免直接暴露类的内部字段：

1. 修改Form2，添加带参数的构造函数，用私有字段存储传入的数据：

public partial class Form2 : Form
{
    private Employee _personalDetail;

    // 新增接收Employee对象的构造函数
    public Form2(Employee emp)
    {
        InitializeComponent();
        _personalDetail = emp;
    }
  
    private void Form2_Load(object sender, EventArgs e)
    {
        textBox1.Text = _personalDetail.EmployeeID.ToString();
        textBox2.Text = _personalDetail.Name;
        textBox3.Text = _personalDetail.Age.ToString();
    }
}

2. 修改Form1的btnSend_Click方法，创建Form2实例时直接传入数据：

private void btnSend_Click(object sender, EventArgs e)
{
    personalDetail.EmployeeID = Convert.ToInt32(txtEmployeeID.Text);
    personalDetail.Name = txtName.Text;
    personalDetail.Age= Convert.ToInt32(txtAge.Text);

    // 通过构造函数传递Employee对象
    Form2 frm = new Form2(personalDetail);
    frm.ShowDialog();
}

额外优化：给Employee类添加public修饰符 #

当前Employee类默认是internal级别，若后续需要跨程序集访问，建议显式添加public修饰符：

public class Employee
{
    public int EmployeeID { get; set; }
    public string Name { get; set; }
    public int Age { get; set; }
}

内容的提问来源于stack exchange，提问作者Dhinesh R