string str = "1,2,3,4,5,6";怎么计算此字符串中逗号的个数？方法1：string str = "1,2,3,4,5,6";int count = str.Count(ch => ch == ',');//count=5方法2：str.Split(',').Length-1方法3：string str = "1,2,3,4,5,6";int count = str.Length - str.Replace(",", "").Length;方法4：Regex.Matches(str,@",").Count方法5：str.ToCharArray().Where(x=x.Equals(',')).ToArray().length