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TonyLoco23
06-27-2011, 02:26 PM
How can I call a Javascript function from my VB.Net code?

I have built a ASP.Net website in VS2005. It is one of those set-ups where you have 2 seperate files for the webpages: i.e. Default.aspx and Default.apsx.vb.

I need to be able to call a JavaScript function from within my VB code, also I need to pass a string variable into the JavaScript function. The JavaScript code is currently sitting at the top of the Default.aspx page whereas the VB code is in the Default.apsx.vb page.


Additional info (if it helps):

What the VB code does is take a user-inputed address and find it in a database and returns certain info about the address. I am trying to improve it to display a Google Map of the address using the Google Maps JavaScript API.

I already have the javascript function ready to go that takes a string address and makes and displays a google map of it, I just need to be able to call it after the user has entered their address.
Ribeyed
06-28-2011, 06:18 AM
Hi,

you can build your javascript in your code behind then register it as a startup script.

some example code in c#



private void Button1_Click(object sender, System.EventArgs e)
{
string javaScript =
"<script language=JavaScript>\n" +
"alert('Button1_Click client-side');\n" +
"</script>";

RegisterStartupScript("Button1_ClickScript", javaScript);
}


regards


Ribs
TonyLoco23
06-28-2011, 08:12 AM
Actually I have been thinking about this some more and it seems that the most sensible way to do it is to do the reverse. I.e. to pass the address to the webpage and have the javascript function pick up the address and run everytime the webpage is refreshed.

So in other words, each time the user enters an address, that address would be stored in a hidden textbox or a cookie or something, then when the page is refreshed the javascript function grabs the address from the hidden textbox/cookie and runs it.

But what would the JavaScript syntax be to retrieve the address from the hidden textbox or cookie? Something like "getElementbyID("Name of text box")"???
Michael_G
07-11-2011, 12:56 PM
You can get the value of a form element completely within the Javascript scope and, then you can pass it to a URL as a URL variable which can then be processed with the ASP.NET code. That is one way to do it, probably the simplest, although there are other ways to do it also. Also a hidden form element will be processed by ASP.NET in the same way that a form element of type text is processed.

You can access the value of a form element using getElementById, even if the form element is type HIDDEN, this is actually done quite often in web application development.

Here is a simple example of using getElementById with a form element. It is very important that your form element has an ID attribute, or else the javascript will fail.

<html>
<head>

<script languague="javascript">
function ProcessForm() {
var Address = document.getElementById("address").value;
if (Address != "") {
alert("Address:" + Address);
return true;
} else {
return false;
}
}
</script>

</head>
<body>

<form method="post" onsubmit="return ProcessForm();">
Address: <input type="text" name="address" id="address" value="" />
<input type="submit" value="Submit">
</form>

</body>
</html>

Michael G. Workman
michael.g.workman@gmail.com