在另一个用户控件中使用一个用户控件的自定义事件？

Question

In UserControl1 there is a custom event which I want to wire in UserControl2.

in UserControl1 I have declared the custom event as:

 public event MYDelegate SendMessage;

while my delegate defination is in other class library as:

public delegate string MYDelegate(string message);

I am firing SendMessage in my code as below:

  SendMessage(txt.Text);

Kindly guide me how to wire SendMessage() event in UserControl2. My idea was do something like in below example but not sure how to get/ access UserControl1 object in UserControl2.

Please help me.

UserControl1.SendMessge+=ListnerMetod();

Answer 1

You are almost there. You just need to attach SendMessage to UserControl2's ListnerMetod.

As Mark Hall said, it is not a good practice to fire an event from one control to another without parent page knowing.

Here is the sample code of firing an event through a parent page.

Default.aspx (Parent Page)

<%@ Register Src="SenderUserControl.ascx" TagName="SenderUserControl" 
  TagPrefix="uc1" %>
<%@ Register Src="ReceiverUserControl.ascx" TagName="ReceiverUserControl" 
  TagPrefix="uc2" %>
<uc1:SenderUserControl ID="SenderUserControl1" runat="server" />
<uc2:ReceiverUserControl ID="ReceiverUserControl1" runat="server" />

public partial class _Default : Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        SenderUserControl1.SendMessage += m => ReceiverUserControl1.ListnerMethod(m);
    }
}

SenderUserControl.ascx

public delegate void MessageHandler(string message);

public partial class SenderUserControl : System.Web.UI.UserControl
{
    public event MessageHandler SendMessage;

    protected void Button1_Click(object sender, EventArgs e)
    {
        SendMessage("test");
    }
}

ReceiverUserControl.ascx

public partial class ReceiverUserControl : System.Web.UI.UserControl
{
    public void ListnerMethod(string message)
    {

    }
}

Credit to Mark Hall

Answer 2

如果两个UserControl都由同一父控件承载，则将父控件中的处理程序附加到要订阅的UserControls事件，然后在该处理程序的第二个UserControl中调用一个方法。