参考 https://www.cnblogs.com/kakakade/p/4562467.html
https://www.cnblogs.com/tonysuen/archive/2010/03/04/1678447.html
Length IndexOf Substring() split join Equals CompareTo EndsWith Insert Remove Replace PadLeft PadRight Concat ToUpper ToLower Trim TrimEnd
StringBuilder
EnsureCapacity Append AppendFormat Insert Remove Replace