C# dynamically add event handler

问题:

Hi i have a simple question. here is my code:

        XmlDocument xmlData = new XmlDocument();
        xmlData.Load("xml.xml");

        /* Load announcements first */
        XmlNodeList announcements = xmlData.GetElementsByTagName("announcement");

        for (int i = 0; i < announcements.Count; i++)
        {
            ToolStripMenuItem item = new ToolStripMenuItem();

            item.Name = announcements[i].FirstChild.InnerText;
            item.Text = announcements[i].FirstChild.InnerText;

            /* HERE IS WERE I NEED HELP */

            item.Click += new EventHandler();

            this.freedomMenu.Items.AddRange(new System.Windows.Forms.ToolStripItem[] { item });
        }

The xml LastChild holds information for each annoucement. I would like to create a click event handler where when teh list item is clicked, a message box shows up with the data inside it. My problem is i dont no how to dynamically generate event handlers to do this :(

回答1:

try:

 /* HERE IS WERE I NEED HELP */

 item.Click += new EventHandler(toolStripClick);

actual handler:

void toolStripClick(object sender, EventArgs e)
{
     ToolStripItem item = (ToolStripItem)sender;
     MessageBox.Show(item.Text);
}    

回答2:

You could use the Tag property of the ToolStripMenuItem:

item.Tag = Announcements[i].LastChild.InnerText;

public void item_click(object sender, EventArgs e)
{
    var menu = sender as ToolStripMenuItem;
    if (menu!= null)
        MessageBox.Show(menu.Tag);
}

Or you could use a lambda, which will capture the variable:

string data = Announcements[i].LastChild.InnerText;
item.Click += (s, e) => { MessageBox.Show(data); };

回答3:

Well, if I understand your question correctly, your "needs help" section should become this:

item.Click += new EventHandler(item_click);

then you just need to add a function to your class:

public void item_click(object sender, EventArgs e)
{
   //do stuff here
}

回答4:

are you asking for the signature for the click event? if you're working in visual studio, you should be able to type

item.Click+= tab tab

and it'll generate something for you

回答5:

I would recommend you look into subscriptions for events. In the event you have to make sure it's the last item in the menu item.
Look at MSDN's help for the item