Ext.NET is an ASP.NET Component framework that integrates the Sencha Ext JS JavaScript framework. It allows the Ext JS user interface to be built declaratively using ASP.NET tag based markup, code-behind or inline fluent syntax, rather than programmatically through JavaScript.

Full source code samples available in the Ext.NET Examples Explorer. Online API docs at http://docs.ext.net/.

Rather than writing JavaScript code similar to:

var win = new Ext.Window({
    id     : 'win-id',
    width  : 400,
    height : 300,
    title  : 'Window Title',
    loader : { 
        url: 'http://www.lipsum.com/',
        autoLoad: true
    }
});

Markup such as the following can be written:

<ext:Window 
    ID="win-id" 
    runat="server" 
    width="400" 
    height="300" 
    title="Window Title">
    <Loader
        runat="server"
        Url="http://www.lipsum.com/"
        AutoLoad="true" />
</ext:Window>

Code-behind such as the following can be written:

var win = new Window {
    ID = "win-id",
    Width = 400,
    Height = 300,
    Title = "Window Title",
    Loader = new ComponentLoader()
    {
        Url = "http://www.lipsum.com/",
        AutoLoad = true
    }
};

RazorView such as the following can be written:

@(Html.X().Window()
    .ID("win-id")
    .Width(400)
    .Height(300)
    .Title("Window Title")
    .Loader(new ComponentLoader()
    {
        Url = "http://www.lipsum.com/",
        AutoLoad = true
    })
)