Can't call javascript function in ASP.NET cs page

Question

I have below JavaScript function in my aspx page:

<script>
    function ShowMessage() {
        alert("Hello World");
    }
</script>

I want to use this function in my cs page on button click event:

<asp:Button ID="MyButton" runat="server" Text="Click Here" OnClick="MyButton_Click" />

Now this code works fine:

Page.ClientScript.RegisterStartupScript(this.GetType(), "myScript", "alert('Hello World');", true);

But this code dose not work:

Page.ClientScript.RegisterStartupScript(this.GetType(), "myScript", "ShowMessage();", true);

What's wrong in my code? What's the possible reason?

Whats the error you are getting? Please check the source html in browser to check if the file has ShowMessage function. — Hector Barbossa
– Hector Barbossa, Commented Jun 15, 2016 at 18:46
Use the browser's dev-tools to see the javascript console. Any errors mentioned there? — Hans Keﬆing
– Hans Keﬆing, Commented Jun 17, 2016 at 6:35

mariocatch · Accepted Answer · 2016-06-15 18:47:40Z

1

You need to expose your ShowMessage() function to a scope that your DOM has access to.

You can try:

window.ShowMessage = function() {
  alert("Hello World");
}

Another option is to move your <script></script> containing your function ABOVE the DOM element that needs it:

<script>
  function Foo() {
    alert('Bar');
  }

</script>

<button onclick="Foo()"></button>

answered Jun 15, 2016 at 18:47

mariocatch

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Comments

mirko cro 1234 · Accepted Answer · 2016-06-17 06:29:31Z

1

You can use onclientclick

<asp:Button ID="MyButton" runat="server" Text="Click Here" onclientclick="ShowMessage()" />

answered Jun 17, 2016 at 6:29

mirko cro 1234

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1 Comment

Hans Keﬆing Over a year ago

The OP might want a server-side event, to execute some server code before that message shows.

H. Pauwelyn · Accepted Answer · 2016-06-17 06:00:54Z

0

Try this:

<script>
    $('#idOfButton').click(
        function() {
            alert("Hello World"); 
        }
    );
</script>

Note: use JQuery for this code and paste this on the end of your HTML page.

Hope this will help

answered Jun 17, 2016 at 6:00

H. Pauwelyn

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1 Comment

Hans Keﬆing Over a year ago

The OP might want a server-side event, to execute some server code before that message shows.

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