First, please see my comment to the question: in the scope of it, there is no such thing as "DOS". (And that was a root cause of your mistake.)
Now, to fix your problem you just need to understand that you don't need "CMD.EXE". This is nothing but yet another program which is irrelevant to the problem you are trying to solve: starting an application.
So, all you need is this:
string app = "edit";
string strCmdLine = "kiran.txt";
Now, I don't know what is "edit", but is this is some text editor, chances are, you don't really want to start it; it won't be able to collaborate with your application. It would be more reasonable to create a UI application (WPF or
) and embed a simple edit control like
in your application.