Simple Console Application using Arrays in C#

this Program collects information about products in stock at the end of each month. The program should incorporate the following functionality.
Store a maximum of 100 product records containing the following.
  • Product Name – must not be left blank.
  • Product Code: - must be exactly 4 characters and must start with either A, C or P followed by only digits..
  • Wholesale price per item: - must be a positive numeric value only.
  • Number of items in stock: - must be a positive numeric value only.
Provide functions to Add, Search, Display and Delete products and enable the user to calculate and display for any selected product:
  • Retail value per item
  • Total wholesale value for the product
  • Total retail value for the product
  • Unrealized profit for the product. (ie. total retail value – total wholesale value) 
This program operate via a menu system. Menu option entries may be in upper or lower case. The menu to control the program are as follows:
  • Add a product (a)
  • Find a product (f)
  • Enter the quantity in stock (q)
  • Delete a product (d)
  • Calculate and display values (v)
  • Exit (x)