C#生成随机数或随机字母

/// <summary>
/// 生成随机数字
/// </summary>
/// <param name="length">生成长度</param>
/// <returns></returns>
public static string Number(int Length)
{
    return Number(Length, false);
}

/// <summary>
/// 随机数字
/// </summary>
/// <param name="Length">生成长度</param>
/// <param name="Sleep">是否要在生成前将当前线程阻止以避免重复</param>
/// <returns></returns>
public static string Number(int Length,bool Sleep)
{
    if(Sleep)
        System.Threading.Thread.Sleep(3);
    string result = "";
    System.Random random = new Random();
    for (int i = 0; i < Length; i++)
    {
        result += random.Next(10).ToString();
    }
    return result;
}

/// <summary>
/// 随机字母
/// </summary>
/// <param name="IntStr">生成长度</param>
/// <returns></returns>
public static string Str_char(int Length)
{
    return Str_char(Length, false);
}

/// <summary>
/// 随机字母
/// </summary>
/// <param name="Length">生成长度</param>
/// <param name="Sleep">是否要在生成前将当前线程阻止以避免重复</param>
/// <returns></returns>
public static string Str_char(int Length, bool Sleep)
{
    if (Sleep) System.Threading.Thread.Sleep(3);
    char[] Pattern = new char[] { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z' };
    string result = "";
    int n = Pattern.Length;
    System.Random random = new Random(~unchecked((int)DateTime.Now.Ticks));
    for (int i = 0; i < Length; i++)
    {
        int rnd = random.Next(0, n);
        result += Pattern[rnd];
    }
    return result;
}

/// <summary>
/// 随机字母+数字
/// </summary>
/// <param name="IntStr">生成长度</param>
/// <returns></returns>
public static string Str(int Length)
{
    return Str(Length, false);
}

/// <summary>
/// 随机字母+数字
/// </summary>
/// <param name="Length">生成长度</param>
/// <param name="Sleep">是否要在生成前将当前线程阻止以避免重复</param>
/// <returns></returns>
public static string Str(int Length, bool Sleep)
{
    if(Sleep)
        System.Threading.Thread.Sleep(3);
    char[] Pattern = new char[] { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z' };
    string result = "";
    int n = Pattern.Length;
    System.Random random = new Random(~unchecked((int)DateTime.Now.Ticks));
    for (int i = 0; i < Length; i++)
    {
        int rnd = random.Next(0,n);
        result += Pattern[rnd];
    }
    return result;
}