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Posted by Andy Brown on 17 October 2012
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Another Nail in the C# Coffin - User Control Events
One of the great pleasures of blogging is that it gives you a platform for your pet rants, and I'm going to return to one of mine: the awfulness of C#.
To add to all of the previous points, consider how to raise events from user controls in ASP.NET. Let's look at how you do this in VB, then compare this with C#.
The VB Method
In VB, you declare the events that you want to raise at the top of the user-control's code:
Imports System.Data
Partial Class blog_ucTaskSearch
Inherits System.Web.UI.UserControl
Public Event Searching(ByVal StatusId As Integer,
ByVal ContainsText As String)
When you want to raise an event, you do so by ... raising the event:
Protected Sub btnSearch_Click(ByVal sender As Object,
ByVal e As System.EventArgs) Handles btnSearch.Click
'search for this information
RaiseEvent Searching(StatusId, txtContains.Text)
End Sub
You can then write an event-handler for this event in the containing page:
Protected Sub ucTaskSearch1_Searching(ByVal StatusId As Integer,
ByVal ContainsText As String) Handles ucTaskSearch1.Searching
There's a whole lot going on here behind the scenes, but the point is that you don't need to know about this!
The C# Method
Now compare that with raising events from user controls in C#. First you have to declare something called delegates (function pointers in old C):
using System;
using System.Collections.Generic;
using System.Data;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
public delegate void ucTaskSearch_SearchHandler(
int StatusId, string ContainsText);
public partial class ucTaskSearch : System.Web.UI.UserControl
{
You then have to declare events which can be raised from the user control:
public event ucTaskSearch_SearchHandler Searching;
You're now finally read to raise an event from the user control (although you should first check that the event-handler has been set in the containing page):
protected void btnSearch_Click(object sender, EventArgs e)
{
// search for this information
if (this.Searching != null)
{
this.Searching(StatusId, txtContains.Text);
}
}
You then have to attach an event-handler to the user control where you declare it on the main page:
The Searching event will be handled by the SearchingHandler routine.
You can then write a routine to handle the user control's event in the main page:
public void SearchingHandler(int StatusId, string ContainsText)
{
The above approach is - to my mind - the simplest one you can take, but it's not the one recommended by C# purists (this involves creating classes which inherit from the EventArgs base class ... you don't want to know).
There - rant over!