c# - EventArgs 不包含采用 1 个参数的构造函数

Question

我找不到与我的匹配的特定问题，我认为这与我正在创建 EventArgs 的子类与一个参数(一个字符串)这一事实有关。当我尝试编译时，它似乎告诉我 ScanInfoEventArgs 没有一个构造函数，而它显然有(至少对我来说很清楚)。

我只包含了我认为适用的部分代码。看似如此简单的事情，让我不知所措。

 public partial class MainWindow : Window
{
    Coffee coffeeOnHand;
    SweetTea sweetTeaOnHand;
    BlueberryMuffin blueberryMuffinOnHand;

    public MainWindow()
    {
        InitializeComponent();

        //The following reads the inventory from file, and assigns each inventory item to the Coffee, SweatTea 
        //and BlueberryMuffin objects in memory.
        using (Stream input = File.OpenRead("inventory.dat"))
        {
            BinaryFormatter formatter = new BinaryFormatter();
            coffeeOnHand = (Coffee)formatter.Deserialize(input);
            sweetTeaOnHand = (SweetTea)formatter.Deserialize(input);
            blueberryMuffinOnHand = (BlueberryMuffin)formatter.Deserialize(input);
        }

        //The following adds whatever information is loaded from the objects on file from above
        //into the dropdown box in the menu.
        SelectedItemDropdown.Items.Add(coffeeOnHand);
        SelectedItemDropdown.Items.Add(sweetTeaOnHand);
        SelectedItemDropdown.Items.Add(blueberryMuffinOnHand);
    }

    public class ScanInfoEventArgs : EventArgs
    {
        ScanInfoEventArgs(string scanType)
        {
            this.scanType = scanType;
        }
        public readonly string scanType;
    }

    public class Scan
    {
        //Delegate that subscribers must implement
        public delegate void ScanHandler (object scan, ScanInfoEventArgs scanInfo);

        //The event that will be published
        public event ScanHandler onScan;

        public void Run()
        {
            //The ScanInfoEventArgs object that will be passed to the subscriber.
            ScanInfoEventArgs scanInformation = new ScanInfoEventArgs("scanType");

            // Check to see if anyone is subscribed to this event.
            if (onScan != null)
            {
                onScan(this, scanInformation);
            }
        }
    }

Answer 1

你需要让你的构造函数public。所有类成员默认为 private，这意味着外界无法访问它们。

由于编译器没有看到匹配的 public 构造函数(代码实际上可以调用的构造函数)，它抛出了您看到的错误。

正确的代码:

    public ScanInfoEventArgs(string scanType)
    {
        this.scanType = scanType;
    }

请注意，如果所有代码都位于同一个程序集中，internal 也可以正常工作。