Contractor To permanent Employee

Hi All,

I have one scenario in which I have to write a code for  contractor who are getting promoted to employee in a company for this i have to check whether the Employee ID of the contractor and the newly created employee record  are same.

If they are same it indicates the contractor and employee are the same person for this I have to just update the Employee No of the user .

I need someone to guide me on how to fetch Employee No from application and update its new value entered from client side