Event question

**=?Utf-8?B?YnJ1Y2UgYmFya2Vy?=** · Oct 15 '08, 05:35 PM

RE: Event question

events are pretty simple.

an event is just a collection of delegates (functions to call).
if you have an object that wants to raise events, that object defines a
public event (any name you want). when the object wants to raise events it
calls the delegates stored in its event object. the event will be null if no
delegates have been added. by convention, the routine that raises the event
is called OnEventName, and is code like:

public EventHandler MyEvent;
private void OnRaiseMyEvent( EventArgs e)
{
EventHandler handler = MyEvent;
if (handler != null)
handler(this, e);
}

some point in your code when you want to fire the event, it would call
OnRaiseMyEvent.

to subscribe to an event, your code addes a delegate (with the correct
signature) to the event, via the syntax of the language. in c# its one of the
following:

myObject.MyEven t += new EventHandler(my Function);
myObject.MyEven t += delegate(object o, EventArgs e)
{
// code goes here
}
myObject.MyEven t += (o,e) =>
{
// code goes here
}

-- bruce (sqlwork.com)

"tshad" wrote:

I am just getting started with events and had a couple of questions on why
they do what they do.
>
If you have a textbox and you want to handle an event you can just do:
>
this.TextBox2.T extChanged += new
EventHandler(Te xtBox2_TextChan ged);
and then have the function.
>
void TextBox2_TextCh anged(object sender, EventArgs e)
{
Response.Write( this.TextBox2.T ext);
}
>
Here the event is created and tied to the control and function.
>
But if you do it in a user control, the function doesn't seem to be tied to
anything.
>
For example, in my .ascx page I could have this:
public event EventHandler BubbleTextChang ed;
//protected void OnBubbleTextCha nged(EventArgs e)
//{
// //if (BubbleTextChan ged != null)
// //BubbleTextChang ed(this, e);
//}
>
Where I normally wouldn't comment out the function, so it isn't tied to
anything (or doesn't seem to be). And the function seems to always need the
word "on" in front of it.
>
If I had 3 events (and no functions) they would show up in intellisense with
"on" in front of them:
>
public event EventHandler A1;
>
public event EventHandler B1;
>
public event EventHandler C1;
>
public event EventHandler D1;
>
public event EventHandler E1;
>
If I only had the above and nothing more, in my aspx page my intellisense
would show:
>
onA1
onB1
onC1
onD1
onE1
>
Yet in my first example, the event was TextBox2.TextCh anged no
TextBox2.onText Changed or the event that was tied to that:
TextBox2_TextCh anged wasn't onTextBox2_Text Changed.
>
Why is it different?
>
Thanks,
>
Tom
>
>
>

**tshad** · Oct 15 '08, 08:45 PM

Re: Event question

"bruce barker" <brucebarker@di scussions.micro soft.comwrote in message
news:CAB6BA8B-925F-45B5-9336-F6F556FBBEF0@mi crosoft.com...

events are pretty simple.
>
an event is just a collection of delegates (functions to call).
if you have an object that wants to raise events, that object defines a
public event (any name you want). when the object wants to raise events it
calls the delegates stored in its event object. the event will be null if
no
delegates have been added. by convention, the routine that raises the
event
is called OnEventName, and is code like:
>
public EventHandler MyEvent;
private void OnRaiseMyEvent( EventArgs e)
{
EventHandler handler = MyEvent;
if (handler != null)
handler(this, e);
}
>

But in your example you use something different. How does MyEvent know it
is tied to OnRaiseMyEvent? The only place I can see that is in the
OnRaiseMyEvent function:

EventHandler handler = MyEvent;

Whe is that executed to connect the two?

In my code:

public event EventHandler A1;
public event EventHandler B1;
public event EventHandler C1;

Even with out setting up the onA1, onB1 and onC1 - the system seemed to use
those names as defaults since in my other page that used the control,
intellisense was using them.

In you example, you use OnRaiseMyEvent and not OnMyEvent. Does it matter?
You said it was a convention.

I am just trying to understand it here. I don't see anywhere where it says
something like: MyEvent uses OnRaiseMyEvent.

some point in your code when you want to fire the event, it would call
OnRaiseMyEvent.

In the case of a user control, I assume it would be on the User control on
the aspx page (or another ascx page).

>
to subscribe to an event, your code addes a delegate (with the correct
signature) to the event, via the syntax of the language. in c# its one of
the
following:
>
myObject.MyEven t += new EventHandler(my Function);
myObject.MyEven t += delegate(object o, EventArgs e)

Do you use both of these? or just one?

Thanks,

Tom

{
// code goes here
}
myObject.MyEven t += (o,e) =>
{
// code goes here
}
>
>
-- bruce (sqlwork.com)
>
>
"tshad" wrote:
>

>I am just getting started with events and had a couple of questions on
>why
>they do what they do.
>>
>If you have a textbox and you want to handle an event you can just do:
>>
> this.TextBox2.T extChanged += new
>EventHandler(T extBox2_TextCha nged);
>and then have the function.
>>
> void TextBox2_TextCh anged(object sender, EventArgs e)
> {
> Response.Write( this.TextBox2.T ext);
> }
>>
>Here the event is created and tied to the control and function.
>>
>But if you do it in a user control, the function doesn't seem to be tied
>to
>anything.
>>
>For example, in my .ascx page I could have this:
> public event EventHandler BubbleTextChang ed;
> //protected void OnBubbleTextCha nged(EventArgs e)
> //{
> // //if (BubbleTextChan ged != null)
> // //BubbleTextChang ed(this, e);
> //}
>>
>Where I normally wouldn't comment out the function, so it isn't tied to
>anything (or doesn't seem to be). And the function seems to always need
>the
>word "on" in front of it.
>>
>If I had 3 events (and no functions) they would show up in intellisense
>with
>"on" in front of them:
>>
> public event EventHandler A1;
>>
> public event EventHandler B1;
>>
> public event EventHandler C1;
>>
> public event EventHandler D1;
>>
> public event EventHandler E1;
>>
>If I only had the above and nothing more, in my aspx page my intellisense
>would show:
>>
>onA1
>onB1
>onC1
>onD1
>onE1
>>
>Yet in my first example, the event was TextBox2.TextCh anged no
>TextBox2.onTex tChanged or the event that was tied to that:
>TextBox2_TextC hanged wasn't onTextBox2_Text Changed.
>>
>Why is it different?
>>
>Thanks,
>>
>Tom
>>
>>
>>

**bruce barker** · Oct 17 '08, 02:15 AM

Re: Event question

it doesn't. MyEvent is just a collection of delegates. if exposed as as
public property, intellisence knows how to add code to create the
delegate. it names a method OnEventName and uses:

EventName += new EventHandler(On EventName);

this is all with subscribing to an event. this is just a naming
convention that vs uses. i generally use a lambda function or create an
anonymous delegate as I think this is often cleaner if the amount of
code in the delegate is small (couple lines).

at some point the code (often a control) must actually raise the event,
so the delegate(s) will be called. this is when OnRaiseEvent is called.

if you write asp.net controls, the control has interfaces you can
implement, that will be called when it time to raise an event (like
OnChange or OnClick).

-- bruce (sqlwork.com)

tshad wrote:

"bruce barker" <brucebarker@di scussions.micro soft.comwrote in message
news:CAB6BA8B-925F-45B5-9336-F6F556FBBEF0@mi crosoft.com...

>events are pretty simple.
>>
>an event is just a collection of delegates (functions to call).
>if you have an object that wants to raise events, that object defines a
>public event (any name you want). when the object wants to raise events it
>calls the delegates stored in its event object. the event will be null if
>no
>delegates have been added. by convention, the routine that raises the
>event
>is called OnEventName, and is code like:
>>
>public EventHandler MyEvent;
>private void OnRaiseMyEvent( EventArgs e)
>{
> EventHandler handler = MyEvent;
> if (handler != null)
> handler(this, e);
>}
>>

>
But in your example you use something different. How does MyEvent know it
is tied to OnRaiseMyEvent? The only place I can see that is in the
OnRaiseMyEvent function:
>
EventHandler handler = MyEvent;
>
Whe is that executed to connect the two?
>
In my code:
>
public event EventHandler A1;
public event EventHandler B1;
public event EventHandler C1;
>
Even with out setting up the onA1, onB1 and onC1 - the system seemed to use
those names as defaults since in my other page that used the control,
intellisense was using them.
>
In you example, you use OnRaiseMyEvent and not OnMyEvent. Does it matter?
You said it was a convention.
>
I am just trying to understand it here. I don't see anywhere where it says
something like: MyEvent uses OnRaiseMyEvent.
>

>some point in your code when you want to fire the event, it would call
>OnRaiseMyEvent .

>
In the case of a user control, I assume it would be on the User control on
the aspx page (or another ascx page).

>to subscribe to an event, your code addes a delegate (with the correct
>signature) to the event, via the syntax of the language. in c# its one of
>the
>following:
>>
> myObject.MyEven t += new EventHandler(my Function);
> myObject.MyEven t += delegate(object o, EventArgs e)

>
Do you use both of these? or just one?
>
Thanks,
>
Tom

> {
> // code goes here
> }
> myObject.MyEven t += (o,e) =>
> {
> // code goes here
> }
>>
>>
>-- bruce (sqlwork.com)
>>
>>
>"tshad" wrote:
>>

>>I am just getting started with events and had a couple of questions on
>>why
>>they do what they do.
>>>
>>If you have a textbox and you want to handle an event you can just do:
>>>
>> this.TextBox2.T extChanged += new
>>EventHandler( TextBox2_TextCh anged);
>>and then have the function.
>>>
>> void TextBox2_TextCh anged(object sender, EventArgs e)
>> {
>> Response.Write( this.TextBox2.T ext);
>> }
>>>
>>Here the event is created and tied to the control and function.
>>>
>>But if you do it in a user control, the function doesn't seem to be tied
>>to
>>anything.
>>>
>>For example, in my .ascx page I could have this:
>> public event EventHandler BubbleTextChang ed;
>> //protected void OnBubbleTextCha nged(EventArgs e)
>> //{
>> // //if (BubbleTextChan ged != null)
>> // //BubbleTextChang ed(this, e);
>> //}
>>>
>>Where I normally wouldn't comment out the function, so it isn't tied to
>>anything (or doesn't seem to be). And the function seems to always need
>>the
>>word "on" in front of it.
>>>
>>If I had 3 events (and no functions) they would show up in intellisense
>>with
>>"on" in front of them:
>>>
>> public event EventHandler A1;
>>>
>> public event EventHandler B1;
>>>
>> public event EventHandler C1;
>>>
>> public event EventHandler D1;
>>>
>> public event EventHandler E1;
>>>
>>If I only had the above and nothing more, in my aspx page my intellisense
>>would show:
>>>
>>onA1
>>onB1
>>onC1
>>onD1
>>onE1
>>>
>>Yet in my first example, the event was TextBox2.TextCh anged no
>>TextBox2.onTe xtChanged or the event that was tied to that:
>>TextBox2_Text Changed wasn't onTextBox2_Text Changed.
>>>
>>Why is it different?
>>>
>>Thanks,
>>>
>>Tom
>>>
>>>
>>>

>
>

**tshad** · Oct 17 '08, 05:15 AM

Re: Event question

But that was my question. I am not trying to be difficult here, just trying
to understand what you HAVE to do versus what CAN you do.

Convention, means that you don't have to do something - just that everyone
agrees that this is the way we are going to do it. Required means that you
have to do it this way.

If I have a control to put on my page like so:
*************** *************** *************** *
public partial class TextBox : System.Web.UI.U serControl
{
public string Text
{
get { return this.TextBox1.T ext; }
set { this.TextBox1.T ext = value; }
}
public bool AutoPostBack
{
get { return TextBox1.AutoPo stBack; }
set { TextBox1.AutoPo stBack = value; }
}

protected override void OnInit(EventArg s e)
{
this.TextBox1.T extChanged += new
EventHandler(Te xtBox1_TextChan ged);
base.OnInit(e);
}
void TextBox1_TextCh anged(object sender, EventArgs e)
{
OnBubbleTextCha nged(e);
}
public event EventHandler BubbleTextChang ed;
protected void OnBubbleTextCha nged(EventArgs e)
{
if (BubbleTextChan ged != null)
BubbleTextChang ed(this, e);
}
}
*************** *************** *******

And on my .aspx page I have the control as:

<uc1:TextBox ID="TextBox1" runat="server"
OnBubbleTextCha nged="TextChang ed" AutoPostBack="t rue" />

And the .aspx.cs page is:
*************** *************** ************
namespace UserControlEven ts
{
public partial class _Default : System.Web.UI.P age
{
protected void TextChanged(obj ect sender, EventArgs e)
{
Response.Write( "In .aspx page: " + this.TextBox1.T ext);
}
}
}
*************** *************** ***************

This works fine.

But if I change the first set of code to:

*************** *************** ***************
void TextBox1_TextCh anged(object sender, EventArgs e)
{
OnRaiseBubbleTe xtChanged(e);
}
public event EventHandler BubbleTextChang ed;
protected void OnRaiseBubbleTe xtChanged(Event Args e)
{
if (BubbleTextChan ged != null)
BubbleTextChang ed(this, e);
}
*************** *************** *************** *

Now there is NO OnBubbleChanged function. But the page STILL works as if it
is. If you look at the text box on the .aspx page, intellisense still shows
OnBubbleChanged and when I put a break on the first line of the
OnRaiseBubbleTe xtChanged function it stops there ??????

If I change to the TextBox to:

<uc1:TextBox ID="TextBox1" runat="server"
OnRaiseBubbleTe xtChanged="Text Changed" AutoPostBack="t rue" />

It does a post back, but nothing happens.

Why is that?

It now goes to a non-existant method. It is forcing the "On" to precede the
event name, which is fine. But I am trying to understand why and why it
goes to the new function name.

Thanks,

Tom

"bruce barker" <nospam@nospam. comwrote in message
news:ebaOX1$LJH A.2348@TK2MSFTN GP05.phx.gbl...

it doesn't. MyEvent is just a collection of delegates. if exposed as as
public property, intellisence knows how to add code to create the
delegate. it names a method OnEventName and uses:
>
EventName += new EventHandler(On EventName);
>
>
this is all with subscribing to an event. this is just a naming convention
that vs uses. i generally use a lambda function or create an anonymous
delegate as I think this is often cleaner if the amount of code in the
delegate is small (couple lines).
>
at some point the code (often a control) must actually raise the event, so
the delegate(s) will be called. this is when OnRaiseEvent is called.
>
if you write asp.net controls, the control has interfaces you can
implement, that will be called when it time to raise an event (like
OnChange or OnClick).
>
-- bruce (sqlwork.com)
>
>
tshad wrote:

>"bruce barker" <brucebarker@di scussions.micro soft.comwrote in message
>news:CAB6BA8 B-925F-45B5-9336-F6F556FBBEF0@mi crosoft.com...

>>events are pretty simple.
>>>
>>an event is just a collection of delegates (functions to call).
>>if you have an object that wants to raise events, that object defines a
>>public event (any name you want). when the object wants to raise events
>>it
>>calls the delegates stored in its event object. the event will be null
>>if no
>>delegates have been added. by convention, the routine that raises the
>>event
>>is called OnEventName, and is code like:
>>>
>>public EventHandler MyEvent;
>>private void OnRaiseMyEvent( EventArgs e)
>>{
>> EventHandler handler = MyEvent;
>> if (handler != null)
>> handler(this, e);
>>}
>>>

>>
>But in your example you use something different. How does MyEvent know
>it is tied to OnRaiseMyEvent? The only place I can see that is in the
>OnRaiseMyEve nt function:
>>
> EventHandler handler = MyEvent;
>>
>Whe is that executed to connect the two?
>>
>In my code:
>>
> public event EventHandler A1;
> public event EventHandler B1;
> public event EventHandler C1;
>>
>Even with out setting up the onA1, onB1 and onC1 - the system seemed to
>use those names as defaults since in my other page that used the control,
>intellisense was using them.
>>
>In you example, you use OnRaiseMyEvent and not OnMyEvent. Does it
>matter? You said it was a convention.
>>
>I am just trying to understand it here. I don't see anywhere where it
>says something like: MyEvent uses OnRaiseMyEvent.
>>

>>some point in your code when you want to fire the event, it would call
>>OnRaiseMyEven t.

>>
>In the case of a user control, I assume it would be on the User control
>on the aspx page (or another ascx page).

>>to subscribe to an event, your code addes a delegate (with the correct
>>signature) to the event, via the syntax of the language. in c# its one
>>of the
>>following:
>>>
>> myObject.MyEven t += new EventHandler(my Function);
>> myObject.MyEven t += delegate(object o, EventArgs e)

>>
>Do you use both of these? or just one?
>>
>Thanks,
>>
>Tom

>> {
>> // code goes here
>> }
>> myObject.MyEven t += (o,e) =>
>> {
>> // code goes here
>> }
>>>
>>>
>>-- bruce (sqlwork.com)
>>>
>>>
>>"tshad" wrote:
>>>
>>>I am just getting started with events and had a couple of questions on
>>>why
>>>they do what they do.
>>>>
>>>If you have a textbox and you want to handle an event you can just do:
>>>>
>>> this.TextBox2.T extChanged += new
>>>EventHandler (TextBox2_TextC hanged);
>>>and then have the function.
>>>>
>>> void TextBox2_TextCh anged(object sender, EventArgs e)
>>> {
>>> Response.Write( this.TextBox2.T ext);
>>> }
>>>>
>>>Here the event is created and tied to the control and function.
>>>>
>>>But if you do it in a user control, the function doesn't seem to be
>>>tied to
>>>anything.
>>>>
>>>For example, in my .ascx page I could have this:
>>> public event EventHandler BubbleTextChang ed;
>>> //protected void OnBubbleTextCha nged(EventArgs e)
>>> //{
>>> // //if (BubbleTextChan ged != null)
>>> // //BubbleTextChang ed(this, e);
>>> //}
>>>>
>>>Where I normally wouldn't comment out the function, so it isn't tied to
>>>anything (or doesn't seem to be). And the function seems to always
>>>need the
>>>word "on" in front of it.
>>>>
>>>If I had 3 events (and no functions) they would show up in intellisense
>>>with
>>>"on" in front of them:
>>>>
>>> public event EventHandler A1;
>>>>
>>> public event EventHandler B1;
>>>>
>>> public event EventHandler C1;
>>>>
>>> public event EventHandler D1;
>>>>
>>> public event EventHandler E1;
>>>>
>>>If I only had the above and nothing more, in my aspx page my
>>>intellisen se
>>>would show:
>>>>
>>>onA1
>>>onB1
>>>onC1
>>>onD1
>>>onE1
>>>>
>>>Yet in my first example, the event was TextBox2.TextCh anged no
>>>TextBox2.onT extChanged or the event that was tied to that:
>>>TextBox2_Tex tChanged wasn't onTextBox2_Text Changed.
>>>>
>>>Why is it different?
>>>>
>>>Thanks,
>>>>
>>>Tom
>>>>
>>>>
>>>>

>>

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