C# random number, random string generator

private string GetRandomString(int pLength, bool pIncludeNumbers, bool pIncludeCharacters)
{
    //ensure at least one option is selected
    if (!pIncludeNumbers && !pIncludeCharacters)
        return String.Empty;

    StringBuilder result = new StringBuilder();
    Random randomGen = new Random();
    int randomNum;
    int maxRandom;
    int minRandom;

    if (pIncludeNumbers)
        maxRandom = 37;
    else
        maxRandom = 27;

    if (pIncludeCharacters)
        minRandom = 1;
    else
        minRandom = 27;

    for (int counter = 0; counter < pLength; counter++)
    {
        randomNum = randomGen.Next(minRandom, maxRandom);
        if (randomNum < 27)
            result.Append(Convert.ToChar(randomNum + 64)); //65 = A
        else
            result.Append(Convert.ToString(randomNum - 27));
    }
    return result.ToString();
}