Undo & Redo process in c#

but not Google.com.

Well, that problem with Google.com is not Google, it's YOU. If you find that reading and teaching yourself how to do something is very difficult, you are not going to have a job as a programmer for very long.

The ability to do research is one of the top skills you absolutely MUST HAVE to hold on to a software development job, or many other jobs come to think of it.

YOU must develop the skill to do research. There is no getting around this requirement. If you don't, you will devolve into being completely dependent on other people writing your code for you and that's just not going to help you keep your job, not matter what you do.

Google is your friend: Be nice and visit him often. He can answer questions a lot more quickly than posting them here...whether you like it or not.

A very quick search gave over 400,000 hits: Google[^]
Which give you this: Simple Undo/redo library for C#/.NET[^]
This: http://stackoverflow.com/questions/597792/c-how-to-implement-good-and-efficient-undo-redo-functionality-for-a-textbox[^]
And this: http://stackoverflow.com/questions/1915907/best-practice-for-undo-redo-implementation[^]
And...you get the idea.

In future, please try to do at least basic research yourself, and not waste your time or ours.