javascript data-binding asp.net-ajax client-templates

asp.net ajax 4.0 client templates, how to bind a select?

I am trying to create a simple ajax grid that allows me to add and remove rows and also edit some of the columns and have others columns calculated directly based on the input in the others. I thought this would be a nice oppurtunity to play with asp.net ajax 4.0 and the client templates. It works pretty ok but I can't seem to find a way to bind my json data to a . How can I do this?

A normal template looks like this

<div id="authorsTemplate" style="visibility:hidden;display:none;"> 
    <ul> 
        <li>First Name: {{ FirstName }}</li> 
        <li>Last Name: {{LastName}}</li> 
        <li>Url: <a href="{{Url}}">{{Url}}</a></li> 
    </ul> 
</div>

How would I use the data bind syntax with a dropdown

<select id="">
  <option value="1">1</option>
  <option value="2">2</option>
</select>

EDIT: If the select tag had a value attribute the obvious solution would be. Edit2: The syntax below was actually the solution, Thx Roatin, I had no idea the select actually had a value attribute.

<select id="" value="{binding nr}">
    <option value="1">1</option>
    <option value="2">2</option>
</select>

I could maybe use custom javascript to set the selected option but the point is a live binding to my json object the same way you bind to the value of a input tag

Solution

I do not want to populate the dropdown, it is already populated. I want to be able to use the client template binding syntax to get the value from my json object and set the selected element.

In fact, select DOM elements do have a value property (but not exposed as an attribute in the markup). Setting it is equivalent to (and faster than) iterating the child <option>s and setting the selectedIndex to the found option index of the option that has a matching value.

Anyway, here's how to bind to it directly with Sys.Binding (complete test case):

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
    <style type="text/css">.sys-template {display:none}</style>
    <script src="MicrosoftAjax.debug.js"></script>
    <script src="MicrosoftAjaxTemplates.debug.js"></script>

    <script type="text/javascript">
    var dataItem = { Foo: '3' };
    function pageLoad()
    {
        $create(Sys.Binding, {
            target: $get("list"),
            targetProperty: 'value',
            source: dataItem,
            path: 'Foo',
            mode: Sys.BindingMode.twoWay
        });
    }
    </script>
</head>
<body>
  <select id="list">
    <option value="1">One</option>
    <option value="2">Two</option>
    <option value="3">Three</option>
  </select>
</body>
</html>

Here is how to do the same thing declaratively, if you prefer:

<body xmlns:sys="javascript:Sys"
      xmlns:binding="javascript:Sys.Binding"
      sys:activate="*">

  <select id="list"
    sys:attach="binding"
    binding:target="{{ $get('list') }}"
    binding:targetproperty="value"
    binding:source="{{ dataItem }}"
    binding:path="Foo">
    <option value="1">One</option>
    <option value="2">Two</option>
    <option value="3">Three</option>
  </select>

(and of course get rid of the pageLoad JavaScript stuff...)

Both examples set up two-way binding to the dataItem object. You can see when the page loads, the third <option> is selected as that is the option with a value matching dataItem.Foo. When you select a different item from the drop-down, dataItem.Foo updates with the new value selected.

Hope that helps!