Why Does My Random String Generator Return Identical Strings?

Random String Generator Returning Same String

Your goal is to generate two distinct random strings, each with four characters. However, your current code produces two identical strings.

The issue stems from the creation of a new Random instance within the RandomString method. Since this instance is initialized for each call, it generates the same sequence of random numbers, resulting in duplicate strings.

Solution:

To ensure two unique strings, we need to ensure the Random instance is created only once. We can do this by making the instance static and initializing it using a seeded value, such as the current time in ticks:

private static Random random = new Random((int)DateTime.Now.Ticks);

By making the instance static and using a seed, we ensure that the random number sequence is different for each call to the RandomString method, as demonstrated in the modified code below:

private static Random random = new Random((int)DateTime.Now.Ticks);//thanks to McAden
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();
}

// get 1st random string 
string Rand1 = RandomString(4);

// get 2nd random string 
string Rand2 = RandomString(4);

// creat full rand string
string docNum = Rand1 + "-" + Rand2;

With this modification, your code will now generate two distinct random strings each time it is executed.

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