How to pass parameter value of server-side method from JavaScript? [duplicate]

Question

Here is an example:

JavaScript:

 var b = 'Banana';
 var list= <%= getJson() %>; // want to pass b?

C# Method:

 using System.Web.Script.Serialization;
 ....
 public string getJson(string x)
 {
      var list = new List<object>{new []{ "1","Apple"}, new []{ "2",x}};
      return (new JavaScriptSerializer()).Serialize(list);
 }

How can I pass variable b when I call getJson() from JavaScript?

@durbnpoisn: How can I ECHO it? Could you show me code fragment? — lucidgold
– lucidgold, Commented Sep 21, 2015 at 20:37

Basic · Accepted Answer · 2015-09-21 20:47:25Z

1

The problem is, the server-side code executes and generates the page (including the javascript which is just text at this point). The page is then sent to the browser where the javascript is executed.

By that time, it's too late to do anything server-side.

Your options are:

Do a GET/POST/similar of the whole page back to the server, with the new variable from JS in a form field. This is trivial but causes a full-page refresh and is becoming less and less desirable.
Use a Javascript Ajax request to pass the variable back to the server and ask it for updated content. Use the response from the server to update the page for the user

The documentation for how to do the latter using jQuery is available here and there are literally thousands of examples around Stack Overflow.

answered Sep 21, 2015 at 20:47

Basic

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Comments

gregnr · Accepted Answer · 2015-09-21 20:47:09Z

0

Remember, anything called inside the <% ... %> tags get processed on the server side before the page even loads. If you need to dynamically load information from the server based on a variable, you need to make an AJAX request.

If you are able to, the easiest way to do this is with jQuery.

answered Sep 21, 2015 at 20:47

gregnr

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