RandomId 生成随机字符串

代码片段：

#region 私有对象
const string ONE = "{0}";
static RandomId _Rid = new RandomId(0);
readonly static Random _Rand = new Random();
static string ToFormat(int length)
{
    StringBuilder sb = new StringBuilder(length * 3);
    for (int i = 0; i < length; i++)
    {
        sb.Append(ONE);
    }
    return sb.ToString();
}

readonly string _Dict;
readonly int _RMax;
readonly string _Format; 
#endregion