how do i call javascript function at the end of button click in asp.net

Question

I tried

Protected Sub btn_add_question_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btn_add_question.Click
        frm_course.Visible = False
        question_div.Visible = True
        ScriptManager.RegisterClientScriptBlock(btn_add_question, Me.GetType(), "BlockName", "alert('hello world');", True)
    End Sub

and

Protected Sub btn_add_question_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btn_add_question.Click
        frm_course.Visible = False
        question_div.Visible = True
        Page.ClientScript.RegisterStartupScript(Me.GetType, "Javascript", "alert('hello')")
    End Sub

But, alert message is not showing. Need Help !!

 <asp:Button ID="btn_add_question" runat="server" Text="Next" CssClass="btn_submit" Width="101px" />

Use view source on the resultant page and search for alert -- how does it look? — Hogan
– Hogan, Commented Jul 24, 2012 at 18:38
Also, please post the asp code for the button, that might have an error too. — Hogan
– Hogan, Commented Jul 24, 2012 at 18:39
If you don't see alert in the source then this button is not being rendered. Are you sure this control isn't inside another control that is being "hidden" — Hogan
– Hogan, Commented Jul 24, 2012 at 18:59

Icarus · Accepted Answer · 2012-07-24 18:44:15Z

3

You need to add the <script> tags to the function call by passing True as the last parameter to RegisterStartupScript as so:

Page.ClientScript.RegisterStartupScript(Me.GetType, "Javascript", "alert('hello');",True)

UPDATE:

Try this:

ScriptManager.RegisterStartupScript(Me.GetType, "Javascript", "alert('hello');",True)

answered Jul 24, 2012 at 18:44

Icarus

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5 Comments

Ravi Over a year ago

Not helpful, same as it was earlier.

Ravi Over a year ago

i have noticed one thing that, when i commented the frm_course.Visible = False then it showing the alert box, now why i don't know, anybody please explain

Icarus Over a year ago

@coders That doesn't make sense. There should be something else going on. Are you using any sort of UpdatePanel/ScriptManager in your page? I am confident that any of my 2 options will work on pages with updatepagel/scriptmanager and pages without them.

Ravi Over a year ago

yes i accept, your solution is working, but only when i put frm_course.Visible = False line inside the comment. That is why, i'm confused, why is that so.

Icarus Over a year ago

I have the feeling frm_course is your main form and RegisterStartupScript is adding the script inside this form. Since it's invisible is not rendering anything and your script is not firing.

jbabey · Accepted Answer · 2012-07-24 18:40:13Z

-2

add an OnClientClick handler to the button or, better yet, attach the handler through javascript where it should be.

<asp:button id="myButton" runat="server" text="Postback" onclientclick="alert('hello world');" />

if all you are doing is changing some visibility of some elements, you shouldn't even be doing a post back at all. just use an input type="button" and show/hide through javascript.

<input type="button" value="Next" id="btn_add_question" />

document.getElementById('btn_add_question').onclick = function () {
    document.getElementById('frm_course').style.visibility = 'hidden';
    document.getElementById('question_div').style.visibility = 'visible';
    alert('hello world');
};

answered Jul 24, 2012 at 18:40

jbabey

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5 Comments

Hogan Over a year ago

this is vb Handles btn_add_question.Click does this on the server side, you are talking about javascript

jbabey Over a year ago

@Hogan you make a pointless postback to do things you could just do in javascript, it's bad for performance from a code and latency perspective.

Hogan Over a year ago

What you say may be true. HOWEVER, THIS IS STILL THE POSTERS QUESTION. Thus the downvote. There are any number of times I had to post an alert to a page from code behind which could not be done any other way.

jbabey Over a year ago

@Hogan the answer i posted accomplishes exactly the same functionality as what the OP is trying to accomplish, without a postback. how is that a bad thing?

Hogan Over a year ago

Have some imagination there are any number of cases (which have not been simplified to post here) which require the code he is showing.

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