I wanted to create a "Click" event for a textbox in C# (as there isn't any).
So, this way
protected void Page_Load(object sender, EventArgs e)
{
if (Request["__EVENTARGUMENT"] != null && Request["__EVENTARGUMENT"] == "txt1OnClick")
{
txt1_Click();
}
txt1.Attributes.Add("onclick", this.Page.ClientScript.GetPostBackEventReference(txt1, "txt1OnClick"));
}
private void txt1_Click()
{
ImageMap1.ImageUrl = "guide/1.jpg";
}
Then I wanted to load the image without reloading the page.
So I used the AJAX UpdatePanel Control and this worked fine with
protected void Button1_Click(object sender, EventArgs e)
{
ImageMap1.ImageUrl = "guide/1.jpg";
}
But not with the event I created, because the compiler doesn't identify my new events as
a real event or something I couldn't figure out.
I added the button1_click event according to Step 8 of "Refreshing an UpdatePanel Control with an External Button".
The click event of textbox is not shown in this option:
So my question is is there any way to add this event within System.Web.UI.WebControls.TextBox class or, to make this event visible within the above option?
So that I can include click event of the textbox within the Triggers of the update panel.
If you try to create a Click event for a TextBox, every time a user clicks your textbox you'll trigger a postback to the server (even to evaluate if you need to do something as part of handling the event). This is very inefficient - you should handle clicks in the browser, using JavaScript and then trigger the UpdatePanel using client-side logic.
This lets you trigger a call to the server if you need it but avoid it when you don't. If you have a server-side event handler, your code will post back to the server (reloading the page) every time the user clicks the TextBox.
You can read this link (and others) about using __doPostBack() on the client side to trigger an UpdatePanel to perform a postback.
http://encosia.com/easily-refresh-an-updatepanel-using-javascript/
Related
I want to run code in a button event handler but the if(Page.IsPostBack) conditional is running first and contains a redirect so the event never runs.
protected void Page_Load(object sender, EventArgs e)
{
if (Page.IsPostBack)
{
(do some stuff with save button pressed...)
// then return the same page to prevent another post on refresh
Response.Redirect(Request.Url.AbsoluteUri);
}
}
and on that page there is another button that calls a handler:
protected void Export_Click(object sender, EventArgs e)
{
(do other stuff..)
}
Is there a way to run the handler first or a way to check which button was clicked so I can add a conditional to the redirect?
Thanks.
This behavior is actually by design in WebForms. To keep things stateless, a full postback occurs whenever you wish to fire off a server-side event.
So the short answer is no, you cannot force your event to occur before the Page_Load does.
However, you can restructure your design a bit to get the behavior you desire. At the moment, it looks as though you are depending on a PostBack having a occurred to execute your save logic. Instead of handling the logic in your Page_Load event, it could be handled in an event appropriate to how your user is expecting to save.
If saving is triggered through a button press, then moving logic for handling the save and redirect to a Save_Click event will allow other events related to PostBack to execute their own logic as well.
It seems like a straight forward thing, but I can't figure it out.
How can I check if a certain button was clicked from user control?
my user control is uc_test and button name is btnTest .
I assume its some sort of event handler added to uc_test.btnTest ?
I'm working in WinForms.
It sounds like you've created a button but want to make it do something on click. I don't often use Winforms but from memory double-clicking on the control in the form should automatically create a btnTest_Click method. If not, just go to code and put in a method like:
protected void btnTest_Click(object sender, Eventargs e)
{
//do something
}
Then set in the properties of the button the OnClick event to btnTest_Click.
I have built an ascx control that is part of many different components of my application. There is a Previous and Next button on this control, which should be signaled to the parent aspx page. This is done by having the parent page add some Delegates for postbacks, such as OnPreviousClicked, OnNextClicked etc.
Everything in this app is 'ajaxified' with an updatepanel. Now I notice that my app breaks if I don't set the delegates on every single Page_Load call in the parent. In other words, if I don't ALWAYS set the delegates in the Page_Load of the parent aspx, then the ascx ends up with null delegates and an exception. Am I coding stuff correctly?
// inside the control
public event EventHandler OnPreviousClicked;
private void PreviousButton_OnClick(object sender, EventArgs e)
{
if(OnPreviousClicked != null) {
OnPreviousClicked(this, e); // or whatever args you want
}
}
// and inside the Page code-behind
private void Page_Load(...)
{
MyUserControl.OnPreviousClicked += new EventHandler(myHandler);
}
// OR inside the Page aspx, you also could just set the OnPreviousClicked property.
<xx:MyUserControl ID="MyUserControl1" runat="server" OnPreviousClicked="myHandler" />
See http://asp.net-tutorials.com/user-controls/events/.
If all you're doing is signaling the clicking of a button, I would have your ASCX control raise a simple event instead. That way each page can listen for the event if they need to and the controls can function regardless if anybody is listening.
First declare the events in your ASCX codebehind:
public event System.EventHandler NextSelected;
Then you create your button click events that raise the event.
protected void btnNextSelected_Click(object sender, EventArgs e)
{
if (EmployeeSelected != null)
{
NextSelected(this, new EventArgs());
}
}
Then in your parent ASP.Net pages you can add your ASCX control (we'll call it NavControl) and create methods that listen for these events.
NavControl.NextSelected += new EventHandler(NextPageRedirect);
protected void NextPageRedirect(object sender, EventArgs e)
{
Response.Redirect("~/ViewEmployee.aspx", false);
}
Note that with this you don't have to create the event handler or method and you can still use the nav control on your page. It should also eliminate the issues you are having with the delegates.
remember each postback has to restart your code. The event handlers don't get serialized to viewstate so you have to set them up again.
That is the expected behavior in asp.net.
The entire page life cycle occurs even when it is a partial postback (update panel). So in order for the events to fire, you will have to wire them up programmatically during page_load or declaratively in your markup (if those delegates you mentioned are events).
I have a button that calls function A()
When I click on it I want the calls to be made in that order:
A()
Page_Load()
Right now it's doing:
Page_Load()
A()
Is there a way around that or is it just by design and there's nothing I can do about it?
The easiest way to do this would be to use a HTML Submit button and check to see if it is in the Form on every postback in Page_Init
public void Page_Init(object o, EventArgs e)
{
if(!string.IsNullOrEmpty(Request.Form["MyButtonName"]))
{
A();
}
}
And in your ASP.NET code:
<Button Type="Submit" Name="MyButtonName" Value="Press Here To Do Stuff Early!" />
I think that will work.
Control events (such as the click events of buttons) are called after page_load. The controls are not guarenteed to be fully initialized prior to page_load. If you really need to call a function before page_load has been called based on whether a button has been pressed you'll have to examine the request to check if the button has been pressed (basically old school ASP)
You need to call your function in the Page_Init. Page_Init will happen before Page_Load.
Here's an Overview of the ASP.NET Page Lifecycle.
Not exactly: ASP.NET will always call Page_Load before handling postback events like Button_Click.
However, you can accomplish what you want by redirecting to your page after handling the postback event. (Using the Post-Redirect-Get pattern.)
Inside your Page_Load method, you can avoid running any relevant code twice by checking to see if it's a postback first:
if (!this.IsPostBack) {
// Do something resource-intensive that you only want to do on GETs
}
As Jeff Sternal answered, The Post-Redirect-Get pattern is a good way of solving a problem like this.
In my circumstances i had a calendar and if you clicked a date it would add that to a scheduler. The scheduler would have buttons on each new date that needed to have onclick functions tied to them.
Because the new row was being added with a linkbutton(on the calendar), in the code the new scheduler date was being added at the Postback event handling meaning that the new set of buttons wouldn't have a command tied to them.
The page life Cycle
Post Get Redirect
I don't think it's possible, at least, not in the way described by your question. When you click a button it will send a request to the server which in turn will start processing it, and follow the ASP.NET Page Lifecycle as posted by Joseph.
Alternatively you could try making an AJAX call to a page without reloading the current one you're on and do whatever processing you require.
This is what you want to do for Page Init is called before Page Load.
Take a look at the ASP.net Page Life Cycle
public void Page_Init(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{
//CALL YOU FUNCTION A()
}
}
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{
}
}
If your actual goal here is to have your "page loading code" happen after your event handler runs -- for example, if clicking your button changes something in your database, and you want the updated data to be reflected on the page when it loads -- then you could have your "page loading code" get called from a method that gets called later in the ASP.NET page life cycle than your event handler, such as Page_PreRender, instead of calling it from Page_Load.
For example, here's a simplified excerpt from an .aspx.cs page class that has a button event handler that runs before the page population logic, and a confirmation message that is visible on the page only after the button was clicked:
// Runs *before* the button event handler
protected void Page_Load() {
_myConfirmationMessage.Visible = false;
}
// Runs *after* the button event handler
protected void Page_PreRender() {
// (...Code to populate page controls with database data goes here...)
}
// Event handler for an asp:Button on the page
protected void myButton_Click(object sender, EventArgs e) {
// (...Code to update database data goes here...)
_myConfirmationMessage.Visible = true;
}
I want to assign property value on button click in aspx page and want to pass the value to the usercontrol and than bind data according to the Property value.
But the problem is before button click event is fired the page_load of user control is invoved ? is the any way to call the page_load of user control again on button click or is there anyother alternative to do it ?
Thanks
Utilizing Page_Load from a UserControl makes the control very dependant on the page life cycle and thus not very flexible. A better way would be to add a public method to the control that you call from the button OnClick event. That method would then perform the data binding.
Kinda like this:
//MyPage.aspx
void Button_OnClick(object sender, EventArgs e)
{
MyUserControl.DataBind(MyTextBox.Text);
}
//MyUserControl.ascx
public void DataBind(string value)
{
UpdateView(value);
}
This is kludgy, but if you have to you can always call the Page_load event manually after the button fires.
A better approach would be: depending on what code needs to fire after the button_click event, you can move it to another event handler, like the OnPreRender method.