c# - getting the same random number repeatedly [duplicate]

Answer 1

You shouldn't create a new Random object every time you need a random number.

Random rnd = new Random();

uses the current time to initialize the LFSR, when the program runs at full speed, the same "current time" gets used many times in a row.

Answer 2

The loop in backgroundWorker1_DoWork is so fast that the Random object generated in generateCode is always seeded with the same value, thus producing the same values. Don't recreate the Random object but assign one to an instance variable in the constructor of your class and only use that one.