Pass C# Values To Javascript

Question

On loading the page I want to pass a value to my javascript function from a server side variable.

I cannot seem to get it to work this is what I have:

Asp.Net

protected void Page_Load(object sender, EventArgs e)
{
    string blah="ER432";
}

Javascript

<script type="text/javascript">

    var JavascriptBlah = '<%=blah%>';

    initObject.backg.product_line = JavascriptBlah;

</script>

Adding this to the page

 public string blah { get; set; }


        protected void Page_Load(object sender, EventArgs e)
        {
           blah="ER432";
        }

I still am getting an error: CS0103: The name 'blah' does not exist in the current context

Also I would like to try and accomplish this without using hdden fields

Just to be certain, the script tag is in the page that has the .aspx.cs containing public string blah { get; set; } declared in it and the page has declared that .aspx.cs file as its code behind right? — mlorbetske
– mlorbetske, Commented Jun 13, 2012 at 19:17

Nick Rolando · Accepted Answer · 2012-06-13 18:52:54Z

11

I believe your C# variable must be a class member in order to this. Try declaring it at the class level instead of a local variable of Page_Load(). It obviously loses scope once page_load is finished.

public partial class Example : System.Web.UI.Page
{
    protected string blah;

    protected void Page_Load(object sender, EventArgs e)
    {
        blah = "ER432";
        //....

edited Jun 13, 2012 at 18:52

answered Jun 13, 2012 at 18:29

Nick Rolando

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7 Comments

Nick LaMarca Over a year ago

I am getting this error:CS0103: The name 'blah' does not exist in the current context

Nick Rolando Over a year ago

You must be doing something wrong. Are you doing it similar to my recent edit? I have tested that and it works fine.

Nick LaMarca Over a year ago

Is my javascript right? It says blah is not in current context

Nick LaMarca Over a year ago

Ahhhhh! I had the code in a web form and the js in the master page. It worked fine Thanks

Nick Rolando Over a year ago

@RyanSammut Not unless the variable is in the master class, I don't think so.

|

mlorbetske · Accepted Answer · 2012-06-13 18:29:49Z

3

In this particular case, blah is local to Page_Load you'll have to make it a class level member (probably make it a property) for it to be exposed like that.

answered Jun 13, 2012 at 18:29

mlorbetske

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Comments

Dante · Accepted Answer · 2012-06-13 18:43:52Z

2

You can put a hidden input in your html page:

<input  type="hidden" runat='server' id="param1" value="" />

Then in your code behind set it to what you want to pass to your .js function:

param1.value = "myparamvalue"

Finally your javascript function can access as below:

document.getElementById("param1").value

edited Jun 13, 2012 at 18:43

answered Jun 13, 2012 at 18:35

Dante

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2 Comments

mlorbetske Over a year ago

It's webforms so you'd have to include the runat="server" on your input to make it accessible from server code

boggy Over a year ago

You might need to add ClientIDMode=static otherwise the id is adorned with some internal prefixes.

OnResolve · Accepted Answer · 2012-06-13 18:31:04Z

0

What I've done in the past is what webforms does as it's functionality--creating a hidden field to store values needed by the client. If you're using 4.0, you can set the hidden field client id mode to static to help keep things cleaner as well. Basically, add you value to the hidden field and then from javascript you can get the value or modify it too(in case you want to pass it back) since it's just a dom element.

If you really want to use code--like a variable, it needs to be accessible at the class scope.

answered Jun 13, 2012 at 18:31

OnResolve

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Comments

bluevector · Accepted Answer · 2012-06-13 19:35:50Z

0

Your string blah needs to be a public property of your Page class, not a local variable within Page_Load. You need to learn about scoping.

public class MyPage
{
    public string blah { get; set; }

    protected void Page_Load(object sender, EventArgs e)
    {
        blah = "ER432";
    }
}

edited Jun 13, 2012 at 19:35

answered Jun 13, 2012 at 18:30

bluevector

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1 Comment

Nick LaMarca Over a year ago

This code is not working for me can you please check my javascript, I am getting an error saying "blah" is not in current context

Uwe Keim · Accepted Answer · 2012-07-16 11:24:02Z

0

You should declare blah at class level.

edited Jul 16, 2012 at 11:24

Uwe Keim

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answered Jun 13, 2012 at 18:29

Matthew

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3 Comments

swiftBoy Over a year ago

@Matthew.. thanks for your help, but make sure when answer is single line or less then it should be a comment, hope you got me!

Matthew Over a year ago

@RDC is there a specific rule that says this? I feel my answer solves the exact problem without inendating the reader with useless information.

swiftBoy Over a year ago

@Matthew.. Nope there is no rule like that, even i agree with you that your answer solve the problem so i gave thanks :) , but as you like to help people same way we can make better stack-overflow by managing our Q/A, well..i always Vote up comments those solve the problem or valuable as an answer post.

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