Long类型转换成DateTime类型写法(字符串截取)

c#中字符串截取使用的方法

String substring(int beginIndex)
String substring(int beginIndex, int endIndex)
String.Substring (Int32) 子字符串从指定的字符位置开始。
String.Substring (Int32, Int32) 子字符串从指定的字符位置开始且具有指定的长度。

 

 /// <summary>
        /// Long类型转换为Datetime类型
        /// </summary>
        /// <param name="LongTime"></param>
        private DateTime? LongConvertDateTime(long LongTime)
        {
            try
            {
                DateTime dtime = new DateTime();
                if (LongTime.ToString().Length > 8)
                {
                    StringBuilder sb = new StringBuilder();
                    string str = LongTime.ToString();
                    string y, M, d, HH, mm, ss, Time;
                    y = str.Substring(0, 4);
                    M = str.Substring(4, 2);
                    d = str.Substring(6, 2);
                    HH = str.Substring(8, 2);
                    mm = str.Substring(10, 2);
                    ss = str.Substring(12, 2);
                    Time = sb.Append(y).Append(M).Append(d).Append(HH).Append(mm).Append(ss).ToString();
                    dtime = Convert.ToDateTime(Time);
                }
                else
                {
                    StringBuilder sb = new StringBuilder();
                    string str = LongTime.ToString();
                    string y, M, d, Time;
                    y = str.Substring(0, 4);
                    M = str.Substring(4, 2);
                    d = str.Substring(6, 2);
                    Time = sb.Append(y).Append(M).Append(d).ToString();
                    dtime = Convert.ToDateTime(Time);
                }
                return dtime;
            }
            catch (Exception)
            {

                return null;
            }
        }