Generating random values in static methods seem to cache [duplicate]

Answer 1

Because you are using a new Random() instance for each call. By default it is seeded with the current system time, which means that multiple Random instances created at the same time will give the same values.

Make the Random instance a static field instead to keep it alive between the calls.

Answer 2

You are calling var random = new Random(); to quickly together. Since the default seed is time based, the seed is the same. Better to create this variable once and Random.Next() every time you need it.

public static class DataGenerator
{
    private readonly static Random random = new Random();

    public static string GenerateRandomString(int length)
    {
       //etc etc using random.Next()
    }
}

Answer 3

Problem:

From MSDN

The default seed value is derived from the system clock and has finite resolution. As a result, different Random objects that are created in close succession by a call to the default constructor will have identical default seed values and, therefore, will produce identical sets of random numbers.

Solution: Again from MSDN

This problem can be avoided by using a single Random object to generate all random numbers. You can also work around it by modifying the seed value returned by the system clock and then explicitly providing this new seed value to the Random(Int32) constructor. For more information, see the Random(Int32) constructor.