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C# Why does OnItemDataBound fire before Page_Load?

I have a question about C# repeater. I have default width setting, and it will change base on some conditions in the Page_Load, I want change to be pass to my Image on OnItemDataBound. However, it seems that the OnItemDataBound is firing off before Page_Load because I changed the width to 700 in Page_Load, but when the image is loaded, it is always showing 380 instead. If OnItemDataBound is not the correct function to use, which function should I call so that I can change the image width after the Page_Load (where the custom width is set) is called? I tried OnPreLoad, OnLoad, and none of them worked.
protected int width = 380;
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
width = 700;
}
}
protected void Test_ItemDataBound(object sender, RepeaterItemEventArgs e)
{
RepeaterItem item = e.Item;
if ((item.ItemType == ListItemType.Item) || (item.ItemType == ListItemType.AlternatingItem))
{
Image Image = (Image)e.Item.FindControl("Image");
Image.ImageUrl = Utilities.generateImage();
Image.Width = width;
}
}

Databinding is done on PrerenderComplete event, which is fired on page lifecycle before PageLoad. For more info check https://msdn.microsoft.com/en-us/library/ms178472.aspx#lifecycle_events to see lifecycle events and their order.

If you declare the datasource in markup, it can render everything much earlier since you are not doing a manual databind. This can occur previous to Page_Load.
Try overloading an earlier event, such as OnLoad or OnPreLoad. Both of these occur prior to Page_Load.
If you are explicitly performing databinding and doing it in another event that occurs prior to Page_Load, then you'll have to ensure that the repeater is rebound if you want to change things. Once you call databind, it binds. If you need to change something either do it before or rebind.

You can use Page_Init for this. It fires before ItemDataBound:
protected void Page_Init(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{
// load
}
}
See also:
https://learn.microsoft.com/en-us/previous-versions/aspnet/ms178472(v=vs.100)

Button Submit calls Onload first!

I have a problem with a webform.
My Goal: Intially when a page is loading, it has to load every textbox empty. After filling the info and click submit, it has to get submitted(UpdatePaymentInfo())
Problem: Here, When the user fills the info and clicks Submit,it calls onload function even before the submit button and makes all text box empty.
Here is the code:
protected override void OnLoad(EventArgs e)
{
base.OnLoad(e);
string QueryStringupdatecreditcard1 = Request.QueryString.ToString();
if (String.Equals(QueryStringupdatecreditcard1, "tabID=B"))
{
divTitle.Visible = false;
trmain.Visible = false;
tdOrderSummary.Visible = false;
trCCandBilling.Visible = true;
trtest2.Visible = false;
divUpdatecreditcard.Visible = true;
trusecompaddress.Visible = false;
txtFirstName.Text = "";
txtLastName.Text = "";
txtAddress1.Text = "";
txtAddress2.Text = "";
txtCity.Text = "";
txtZip.Text = "";
txtCardNo.Text = "";
txtVccNumber.Text = "";
trAmountCharged.Visible = false;
}
}
protected void imgbtnSubmit_Click(object sender, ImageClickEventArgs e)
{
try
{
UpdatePaymentInfo();
}
}

Wrap the current contents of your OnLoad method in:
if (!Page.IsPostBack)
{
// Code in here will only be executed when the page is *not* being loaded by a postback
}
This is because, as per the ASP.NET Page Life Cyle, the things that you care about in this instance happen in this order:
Load - During load, if the current request is a postback, control
properties are loaded with information
recovered from view state and control
state.
Postback event handling - If the request is a postback, control event
handlers are called. After that, the
Validate method of all validator
controls is called, which sets the
IsValid property of individual
validator controls and of the page.
So what happens is (somewhat simplified):
You click the image button, triggering the postback.
The data from your form is loaded into your controls.
Your OnLoad method overwrites the values in the controls to clear them.
Your click handler is run, but because of step 3 it sees empty values.
As others have sort-of mentioned, it wouldn't necessarily be a bad thing to refactor your OnLoad method whilst you're doing this. At the moment you seem to have it doing two distinct things:
Clearing the text fields
Setting the visibility of fields
It might be worth separating this into one or two (depending on if the visibility setting and field clearing will be done independently) separate methods and adjusting your OnLoad method so it looks like this:
protected override void OnLoad(EventArgs e)
{
base.OnLoad(e);
if (!Page.IsInPostBack)
{
SetFieldVisibility();
ClearFields();
}
}

Page_Load always occurs.
See the documentation on the Page Lifecycle
What you need to do is check to see if the Page_Load is being triggered by a Postback.
private void Page_Load(object sender, System.EventArgs e)
{
if(!Page.IsPostBack)
{
///do stuff in here that you want to occur only on the first lad.
}
else
}
// code that you want to execute only if this IS a postback here.
{
}
// do stuff you want to do on Page_Load regardless of postback here.
}

You can use the IsPostBack property of the Page as follows:
protected override void OnLoad(EventArgs e) {
if (!Page.IsPostBack) {
EmptyTextBoxes();
}
}

Have you tried wrapping the form reset code in a check to see if the page is a postback?
if(!Page.IsPostback) {
// Do form reset here
}

You thought about using the IsPostBack page variable?
protected override void OnLoad(EventArgs e)
{
if(!IsPostBack){
//all your logic here.
}
}

if it's the case, you might use a databound control and set it to insert mode

the checkbox event is not triggerd?

i have created checkbox event maually.
chkCheckBox1.CheckedChanged += new EventHandler(chkCheckBox1_CheckedChanged);
this event is not triggered,in pageload i have put
(!page.ispostback)
{
}
so when i clik the check box it goes to the page load and not going to the evnt
protected void chkCheckBox1_CheckedChanged(object sender, EventArgs e)
{
..........
}
the checkbox event is not triggerd..

Have you enabled AutoPostBack property on your control?
By default this is set to False when you add a checkbox control to your page. Try setting it to true.

Set the Autopostback property to true.
chkCheckBox1.CheckedChanged += new EventHandler(chkCheckBox1_CheckedChanged);
You have to wire up this event on every call to the page so if you have put this inside of the if(!Page.IsPostBack) then put it outside.
Take a look at this article Adding a dynamic control to a placeholder control and wire up the event. It shows an extra step for making things totally dynamic but the principles stay the same for what you're after.
Grz, Kris.

To trigger the following event
protected void chkCheckBox1_CheckedChanged(object sender, EventArgs e)
{
..........
}
Set the checkbox autopostback property to TRUE

EventHandler is null

I am trying to raise a click event from User control and handle it on the containing page. The problem I have is, when I click the button 'imgstep1' on the user control, the code behind imgstep1_click event triggers and but the 'btnHandler' event is alway null. Hence it doesnt call the parent event.
Any help on this will be much appreciated.
My User Control Code is :
.ascx code:
<asp:ImageButton ImageUrl="./images/step1.gif"
ID="imgstep1" runat="server"
OnClick="imgstep1_Click"/>
.ascx.cs code :
public delegate void OnImageButtonClick();
public event OnImageButtonClick btnHandler;
protected void imgstep1_Click(object sender, ImageClickEventArgs e)
{
if (btnHandler != null)
btnHandler();
}
.aspx page code:
protected void Page_Load(object sender, EventArgs e)
{
ucStepHdr.btnHandler += new StepsHeader.OnImageButtonClick(ucStepHdr_btnHandler);
}
void ucStepHdr_btnHandler()
{
Response.Write ('test');
}

The code looks simple enough to work correctly. The only reason that btnHandler is null could be because the event registration code in the aspx page is not called.
Is there a post back ? Are you sure you are adding the event EACH TIME the page loads ???
ucStepHdr.btnHandler += new StepsHeader.OnImageButtonClick(ucStepHdr_btnHandler);

If you remove OnClick="imgstep1_Click" and you put this in your ascx.cs
protected ImageButton imgstep1;
protected override void OnInit(EventArgs e)
{
this.imgstep1.Click += new ImageClickEventHandler(imgstep1_Click);
}
Does this method of wiring up your event work?

It looks like it should work... can you step through the code in the debugger, and see what the value of ucStepHdr.btnHandler is as soon as you set it in Page_Load? (Just an aside, traditionally these are set in init rather than load, but this isn't your issue.)

C# Dynamically created LinkButton Command Event Handler

So I have a weird situation here... I have an System.Web.UI.WebControls.WebParts.EditorPart class. It renders a "Search" button, when you click this button, it's clickHandler method does a DB search, and dynamically creates a LinkButton for each row it returns, sets the CommandName and CommandArgument properties and adds a CommandEventHandler method, then adds the LinkButton control to the page.
The problem is, when you click a LinkButton, its CommandEventHandler method is never called, it looks like the page just posts back to where it was before the ORIGINAL "Search" button was pressed.
I have seen postings saying that you need to add the event handlers in OnLoad() or some other early method, but my LinkButtons haven't even been created until the user tells us what to search for and hits the "Search" button... Any ideas on how to deal with this?
Thanks!

This is my favorite trick :)
Our scenario is to first render a control. Then using some input from the user, render further controls and have them respond to events.
The key here is state - you need to know the state of the control when it arrives at PostBack - so we use ViewState. The issue becomes then a chicken-and-egg problem; ViewState isn't available until after the LoadViewState() call, but you must create the controls before that call to have the events fired correctly.
The trick is to override LoadViewState() and SaveViewState() so we can control things.
(note that the code below is rough, from memory and probably has issues)
private string searchQuery = null;
private void SearchButton(object sender, EventArgs e)
{
searchQuery = searchBox.Text;
var results = DataLayer.PerformSearch(searchQuery);
CreateLinkButtonControls(results);
}
// We save both the base state object, plus our query string. Everything here must be serializable.
protected override object SaveViewState()
{
object baseState = base.SaveViewState();
return new object[] { baseState, searchQuery };
}
// The parameter to this method is the exact object we returned from SaveViewState().
protected override void LoadViewState(object savedState)
{
object[] stateArray = (object[])savedState;
searchQuery = stateArray[1] as string;
// Re-run the query
var results = DataLayer.PerformSearch(searchQuery);
// Re-create the exact same control tree as at the point of SaveViewState above. It must be the same otherwise things will break.
CreateLinkButtonControls(results);
// Very important - load the rest of the ViewState, including our controls above.
base.LoadViewState(stateArray[0]);
}

You need to re-add the dynamically created controls, in the onload, so that they can be in the page hierarchy and fire their event.

LinkButton link= new LinkButton();
link.Command +=new CommandEventHandler(LinkButton1_Command);
protected void LinkButton1_Command(object sender, CommandEventArgs e)
{
try
{
System.Threading.Thread.Sleep(300);
if (e.CommandName == "link")
{
//////////
}
}
catch
{
}
}

A dirty hack I just came up with, is to create dummy LinkButtons with the same IDs as the real buttons.
So let's say you are going to create a LinkButton "foo" at Pre_Render (which is too late), then also create a dummy foo at Page_Load:
var link = new LinkButton();
link.ID = "foo";
link.Click += fooEventHandler;
dummyButtons.Controls.Add(link);
(Where "dummyButtons" is just a PlaceHolder on the page with Visibility set to false.)
It's ugly, but it works.