C#判断字符串为数字

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public static bool isNumber(string s)
        {
            int flag = 0;
            char[] str = s.ToCharArray();
            for (int i = 0; i < str.Length; i++)
            {
                if (Char.IsNumber(str[i]))
                {
                    flag++;
                }
                else
                {
                    flag = -1;
                    break;
                }
            }
            if (flag > 0)
            {
                return true;
            }
            else
            {
                return false;
            }
        } 

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