How can we write a regular expression for the following

In addition to solution 1 by Prasad Nikumbh[^] i'd recommend to start here: Regular Expression Examples[^]. There's a lot of examples, which may help you to understand how a regular expression work.

Another way to build and test regular expression is to install Expresso Regular Expression Tool[^].

Good luck!

Quote:

I was tried PAN based validation and did some changes for the same,but it didn't worked.

If you show your work, we can explain why it don't work.

Just a few interesting links to help building and debugging RegEx.
Here is a link to RegEx documentation:
perlre - perldoc.perl.org[^]
Here is links to tools to help build RegEx and debug them:
.NET Regex Tester - Regex Storm[^]
Expresso Regular Expression Tool[^]
RegExr: Learn, Build, & Test RegEx[^]
Online regex tester and debugger: PHP, PCRE, Python, Golang and JavaScript[^]
This one show you the RegEx as a nice graph which is really helpful to understand what is doing a RegEx: Debuggex: Online visual regex tester. JavaScript, Python, and PCRE.[^]
This site also show the Regex in a nice graph but can't test what match the RegEx: Regexper[^]

Thank you for all.

I was tried this and it is working perfectly.

[RegularExpression(@"^([0-9]){5}([a-zA-Z]){3}([0-9]){2}?$", ErrorMessage = "Entered CAN is Invalid")]

Ex : 12345ABC12