Basic Crypto for .NET
I am not an expert in cryptography by any stretch of the imagination but I am pretty sure an IV should be randomly generated. 


  " In cryptography, an initialization vector (IV) or starting variable (SV)[1] is a fixed-size input to a cryptographic primitive that is typically required to be random or pseudorandom. Randomization is crucial for encryption schemes to achieve semantic security [...] " -
  
  https://en.wikipedia.org/wiki/Initialization_vector