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

Random String Generator Returning Same String

A common issue encountered with random string generators arises when the generated strings appear identical, even when calling the generator multiple times. This problem stems from the fact that the generator is initialized within the function, resulting in the same set of random values being repeatedly generated.

Solution

To ensure distinct random strings, the Random instance should be created outside the function, where it remains accessible throughout the program's lifecycle. By doing so, the instance retains its state, preventing the generation of identical strings.

Here's an updated version of your code:

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);

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

Now, when you call the RandomString function twice, it will generate two distinct four-character strings, resulting in an output similar to "UNTE-FWNU" instead of "UNTE-UNTE."

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