This is from the msdn article here:
https://blogs.msdn.microsoft.com/tomarcher/2006/05/10/are-hash-codes-unique/
"While you will hear people state that hash codes generate a unique value for a given input, the fact is that, while difficult to accomplish, it is technically feasible to find two different data inputs that hash to the same value. However, the true determining factors regarding the effectiveness of a hash algorithm lie in the length of the generated hash code and the complexity of the data being hashed."
So just use a hash algorithm suitable to your data size and it will have unique hashcodes.