, SteveRichter wrote

using jQuery you can popup a calendar for every date input field in a form. How to do that in WPF? 

dateInput.OnClick += new MouseClickEventHandler( (o,e) => 
{
  new DatePopup(dateInput).Show(e.Location);
});

Or I want to add a link to a table that will export the contents of the table to excel.

var x = new DataGrid();

 

I esp want to be able to do these things without having to be the programmer or have access to the source code of the app.  How does the end user customize their apps to give them what they need without the source code?

this.BackgroundColor = ParseValueOutOfIniFile("config.ini", "bgcolor");

With javascript I can inject code into the browser on the client side to do these things. Not easily or reliably in all cases. Just an example to me where software technology is stagnating at these large companies that control the OSes we use. 

If you want to do that, write a library and expose your code via an interface. Most users don't want to write javascript for your app though,