How to Generate Unique Number of 8 digits?

Question

I am using this code to generate a 8 digit unique number.

byte[] buffer = Guid.NewGuid().ToByteArray();
return BitConverter.ToUInt32(buffer, 8).ToString();
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Answer 1

The range of values is too small. An incrementing counter is the best solution, like in an ERP system - you set the first customer number to 1000 and the next one is 1001, 1002,...,99999999. Otherwise, if you get a random number (or part of GUID) from these, you'll hit the same number again. Depending on your app, sooner or later but it's guaranteed to happen sooner than just iterating over them.