Pass a parameter to server method using JavaScript

Question

I have a public in my code behind page that takes a string. I would like to call this method from javascript.

The parameter that I want to pass down is variable that changes from a ddl.

So I have something like this:

 var value = document.getElementById('ddlContact').value;
        <%=PopulateContactFields("value") %>

This passes down the word 'value' and not the data in value.

I can't figure out the proper syntax to pass down the data in value.

Thanks

Answer 1

As mentioned by others, trying to access C# code behind directly from javascript is impossible.

However, you can communicate with it indirectly.

I think your best shot is to use a combination of jQuery and the [WebMethod] attribute.

javascript function using jQuery to do an AJAX call:

function Search() {
    var search = $('#<%= ddlContact.ClientId %>').val();
    var options = {
        type: "POST",
        url: "Default.aspx/Hello",
        data: "{'name' :'" + search + "'}",
        contentType: "application/json; charset=utf-8",
        dataType: "json",
        success: function(msg) {
            alert(msg);
        }
    };
    $.ajax(options);
}

Code behind:

public partial class _Default : System.Web.UI.Page
{
    [WebMethod]
    public void Hello(string name)
    {
      return "Hi " + name;
    }
}