How to use dhtmlxAjax with monorail & C# instead?

We are using monorail MVC Framework & C# for the web development.

Can you give a sample on usage of dhtmlxAjax in this scenario instead of php?

The dhtmlxAjax is a lib, which can execute POST and GET calls of url provided with specified parameters. It has not any special server side support, and not purposed for usage with custom server side frameworks.
dhtmlxAjax can be used If you need to call some url and retrieve response, its the main purpose of lib.