C# 将 YYYYMMDD 字符串转换为 MM/DD/YYYY 字符串
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Convert YYYYMMDD string to MM/DD/YYYY string
提问by JTRookie86
I have a date that is stored as a string in the format YYYYDDMM. I would like to display that value in a 'MM/DD/YYYY' format. I am programming in c#. The current code that I am using is as follows:
我有一个以 YYYYDDMM 格式存储为字符串的日期。我想以“MM/DD/YYYY”格式显示该值。我正在用 C# 编程。我正在使用的当前代码如下：
txtOC31.Text = dr["OC31"].ToString().Trim();
strOC31date = dr["OC31DATE"].ToString().Trim();
DateTime date31 = DateTime.Parse(strOC31date);
strOC31date = String.Format("{0:MM/dd/yyyy}", date31);
However, I am getting an error because the YYYYMMDD string (strOC31date) is not being recognized as a valid datetime.
但是，我收到一个错误，因为 YYYYMMDD 字符串 (strOC31date) 未被识别为有效的日期时间。
采纳答案by Steve
DateTime.ParseExact with an example
DateTime.ParseExact 示例
string res = "20120708";
DateTime d = DateTime.ParseExact(res, "yyyyddMM", CultureInfo.InvariantCulture);
Console.WriteLine(d.ToString("MM/dd/yyyy"));
回答by Leon
Instead of DateTime.Parse(strOC31date);use DateTime.ParseExact()method, which takes format as one of the parameters.
而不是DateTime.Parse(strOC31date);使用DateTime.ParseExact()方法，它将格式作为参数之一。
回答by James Michael Hare
Use ParseExact()(MSDN) when the string you are trying to parse is not in one of the standard formats. This will allow you to parse a custom format and will be slightly more efficient (I compare them in a blog post here).
当您尝试解析的字符串不是标准格式之一时，请使用ParseExact()( MSDN)。这将允许您解析自定义格式，并且效率会稍微提高一些（我在此处的博客文章中对它们进行了比较）。
DateTime date31 = DateTime.ParseExact(strOC31date, "yyyyMMdd", null);
Passing nullfor the format provider will default to DateTimeFormatInfo.CurrentInfoand is safe, but you probably want the invariant culture instead:
传递null给格式提供程序将默认为DateTimeFormatInfo.CurrentInfo并且是安全的，但您可能需要不变的文化：
DateTime date31 = DateTime.ParseExact(strOC31date, "yyyyMMdd", DateTimeFormatInfo.InvariantInfo);
Then your code will work.
然后您的代码将起作用。
回答by Chris
You want the method DateTime.ParseExact.
您需要DateTime.ParseExact方法。
DateTime date31 = DateTime.ParseExact(strOC31date, "yyyyddMM", CultureInfo.InvariantCulture);
