The Type or Namespace name ' GridAction' could not be found

[Tarang]

I am getting this error "The Type or Namespace name ' GridAction' could not be found" while upgrading the application from version 2011.2.712 to 2018.3.1017.

Please let me know how to solve this error.

[Tsvetina]

Hello Tarang,

The Telerik Extensions for ASP.NET MVC that you previously used in your project were discontinued in 2013 and replaced by UI for ASP.NET MVC, which is built on top of the Kendo UI widgets. 

The GridAction attribute is no longer needed in the UI for ASP.NET MVC Grid. You can see the most common Grid binding setup explained in this article:
Ajax Binding

Also, you can check the Data Binding section of the Grid demos to see this and other binding scenarios:
Grid Binding Demos

Try configuring your Grid according to the documentation/demo examples and let me know if you encounter problems with its binding.

Also, you can check out the documentation elaborating on the differences between the two libraries and the changes needed when upgrading. This is the general set up article:
Telerik Extensions Migration Overview

There are also separate articles for widgets where the differences in API and behavior are listed. For example:
Grid Migration

I hope this information helps.

Regards,
Tsvetina
Progress Telerik