如何删除事件处理程序并将其重新附加到 C# 中的控件？

我读过这个answer https://stackoverflow.com/questions/91778/how-to-remove-all-event-handlers-from-a-control。 它只是告诉我如何从按钮控件中删除单击事件。我想知道如何更改代码（尤其是GetField("EventClick"...部分！）这样我就可以用其他控件做同样的事情。例如，我想删除TextChanged的事件TextBox。 我还想知道如何重新附加事件处理程序。

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

    private void textBox1_TextChanged(object sender, EventArgs e)
    {
        if (textBox1.Text.Length < 10) return;

        MessageBox.Show("do something");
    }

    private void Form1_Load(object sender, EventArgs e)
    {
        Tools.mkTextBoxWithPlaceholder(textBox1, "hi, input here...");
    }
}
class Tools
{
    public static void mkTextBoxWithPlaceholder(TextBox tb, string placeholder)
    {
        tb.Tag = placeholder;
        tb.GotFocus += new EventHandler(tb_GotFocus);
        tb.LostFocus += new EventHandler(tb_LostFocus);
    }

    private static void tb_GotFocus(object sender, EventArgs e)
    {
        TextBox tb = sender as TextBox;
        tb.Clear();
    }
    private static void tb_LostFocus(object sender, EventArgs e)
    {
        TextBox tb = sender as TextBox;

        //TODO Remove the TextChanged event handler here.

        tb.Text = tb.Tag as string;

        //TODO Reattach the TextChanged event handler here.
    }
}

通过上面的代码，textBox1 将具有类似 placeholder 的功能。也许您可以给我一些有关如何将占位符添加到文本框的帮助。这就是我想要的。

Remove

Mybutton.event -= methodname;

Reattach

Mybutton.event += methodname;