How can I manipulate ASP.Net server controls with script code

JCruz063 · Dec 26, 2003

Hi All,
This is driving me insane. People please help me out!

(I'm working with ASP.Net using C#)
I need to manipulate a couple of server-side controls (CheckBox, DropDownList, ListBox, etc) using client-side script. The problem is that the object model of the server-side controls is not accessible via client-side script. For example, in a code-behind class, I could write:

Code:

   //This is C# code
   DropDownList ddl = new DropDownList();
   ddl.Items.Add(...);

In client-side script, however, the story is different. If I were to write the same code I wrote above, I would get an error in the page. So, the question is: How do I interact with server-side controls using client-side script?

Please note that this problem has reached very high frustration levels and that lack of help would cause me to commit suicide (ok, ok, maybe I won't - just help me out)

Thanks!

Jose

LV · Dec 26, 2003

Since all server side controls produce an HTML control(i.e. DropDownList=<select>, ListBox=<select multiple>, CheckBox=<input type=checkbox>), you can as well execute client side javascript, attached to an event of this HTML controls. Here is a sample:

Code:

<html>
<head>
 <script language=javascript>
  function showSelected(ddl){
   alert(ddl.options[ddl.selectedIndex].text);
  }
 </script>
</head>
<body>
 <form id=&quot;Form1&quot; method=&quot;post&quot; runat=&quot;server&quot;>
   <asp:DropDownList id=DropDownList1 runat=&quot;server&quot; />
 </form>
</body>
</html>
code behind:
protected System.Web.UI.WebControls.LinkButton LinkButton1;
	
private void Page_Load(object sender, System.EventArgs e)
{
 if(!Page.IsPostBack)
 {
  for(int i=0;i<5;i++)
  {
   ListItem li = new ListItem(&quot;Item &quot;+i.ToString(), i.ToString());				  
   DropDownList1.Items.Add(li);
  }
}

override protected void OnInit(EventArgs e)
{
  //
  // CODEGEN: This call is required by the ASP.NET Web Form Designer.
  //
  InitializeComponent();
  base.OnInit(e);

  if(DropDownList1.Attributes[&quot;onchange&quot;] == null)
  {
    DropDownList1.Attributes.Add(&quot;onchange&quot;, &quot;javascript:showSelected(this);&quot;);
  }
}

You got the general idea. In the same manner you would execute a client side "onclick" event for a Button control(<input type=button>).

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How can I manipulate ASP.Net server controls with script code

JCruz063

Programmer

LV

Programmer

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