Why Does My Random String Generator Keep Producing the Same String?

Random String Generator Consistency Issue

Problem:

A random string generator is failing to produce distinct strings despite being called multiple times. Instead, it's generating the same random string repeatedly.

Code:

private string RandomString(int size)
{
    StringBuilder builder = new StringBuilder();
    Random random = new Random(); // Random object created each time
    char ch;
    for (int i = 0; i < size; i++)
    {
        ch = Convert.ToChar(Convert.ToInt32(Math.Floor(26 * random.NextDouble() + 65)));                 
        builder.Append(ch);
    }

    return builder.ToString();
}

Reason:

The issue lies in the creation of a new Random object within the RandomString method. This initializes the random number generator with the same seed each time, leading to the same sequence of random numbers and, ultimately, the same random string.

Solution:

To ensure two distinct random strings, the Random object should be created outside the RandomString method and made static. This ensures that the same seed is used throughout the lifetime of the application, producing a consistent sequence of random numbers and distinct strings on each call.

Modified Code:

private static Random random = new Random((int)DateTime.Now.Ticks); // Random object created outside method

private string RandomString(int size)
{
    StringBuilder builder = new StringBuilder();
    char ch;
    for (int i = 0; i < size; i++)
    {
        ch = Convert.ToChar(Convert.ToInt32(Math.Floor(26 * random.NextDouble() + 65)));                 
        builder.Append(ch);
    }

    return builder.ToString();
}

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