Ext.NET is a component framework built with ASP.NET and Sencha Ext JS for quicker, better web app development. Ext.NET is an advanced ASP.NET (WebForms + MVC) component framework integrating the cross-browser Sencha Ext JS jаvascript Library. Ext.NET is built on top of Sencha Ext JS, the popular UI framework. This means all our components come with great theming options, allowing your app to fit together seamlessly with any design aesthetic.