String now = DateTime.Now.ToString("YYYY-MM-DD HH:MI:SS");//make it datetime
DateTime.Parse(now);

这个给了你

2019-08-17 11:14:49.000

你想快点吗?

假设您有一个格式为yyMMdd的日期。

我发现转换它的最快方法是:

var d = new DateTime(
(s[0] - '0') * 10 + s[1] - '0' + 2000, 
(s[2] - '0') * 10 + s[3] - '0', 
(s[4] - '0') * 10 + s[5] - '0')

只需根据您选择的日期格式选择索引。如果你需要速度，你可能不介意函数的“非泛型”方式。

此方法所需时间约为以下操作所需时间的10%:

var d = DateTime.ParseExact(s, "yyMMdd", System.Globalization.CultureInfo.InvariantCulture);

似乎没有人实现过扩展方法。通过@CMS的回答:

工作和改进的完整源代码示例在这里:Gist Link

namespace ExtensionMethods {
    using System;
    using System.Globalization;

    public static class DateTimeExtensions {
        public static DateTime ToDateTime(this string s, 
                  string format = "ddMMyyyy", string cultureString = "tr-TR") {
            try {
                var r = DateTime.ParseExact(
                    s: s,
                    format: format,
                    provider: CultureInfo.GetCultureInfo(cultureString));
                return r;
            } catch (FormatException) {
                throw;
            } catch (CultureNotFoundException) {
                throw; // Given Culture is not supported culture
            }
        }

        public static DateTime ToDateTime(this string s, 
                    string format, CultureInfo culture) {
            try {
                var r = DateTime.ParseExact(s: s, format: format, 
                                        provider: culture);
                return r;
            } catch (FormatException) {
                throw;
            } catch (CultureNotFoundException) {
                throw; // Given Culture is not supported culture
            }

        }

    }
}

namespace SO {
    using ExtensionMethods;
    using System;
    using System.Globalization;

    class Program {
        static void Main(string[] args) {
            var mydate = "29021996";
            var date = mydate.ToDateTime(format: "ddMMyyyy"); // {29.02.1996 00:00:00}

            mydate = "2016 3";
            date = mydate.ToDateTime("yyyy M"); // {01.03.2016 00:00:00}

            mydate = "2016 12";
            date = mydate.ToDateTime("yyyy d"); // {12.01.2016 00:00:00}

            mydate = "2016/31/05 13:33";
            date = mydate.ToDateTime("yyyy/d/M HH:mm"); // {31.05.2016 13:33:00}

            mydate = "2016/31 Ocak";
            date = mydate.ToDateTime("yyyy/d MMMM"); // {31.01.2016 00:00:00}

            mydate = "2016/31 January";
            date = mydate.ToDateTime("yyyy/d MMMM", cultureString: "en-US"); 
            // {31.01.2016 00:00:00}

            mydate = "11/شعبان/1437";
            date = mydate.ToDateTime(
                culture: CultureInfo.GetCultureInfo("ar-SA"),
                format: "dd/MMMM/yyyy"); 
         // Weird :) I supposed dd/yyyy/MMMM but that did not work !?$^&*

            System.Diagnostics.Debug.Assert(
               date.Equals(new DateTime(year: 2016, month: 5, day: 18)));
        }
    }
}

转换。ToDateTime或DateTime。解析

String now = DateTime.Now.ToString("YYYY-MM-DD HH:MI:SS");//make it datetime
DateTime.Parse(now);

这个给了你

2019-08-17 11:14:49.000

使用DateTime.Parse(字符串):

DateTime dateTime = DateTime.Parse(dateTimeStr);