C# 如何转换日期时间？到日期时间
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/1091870/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
How to convert DateTime? to DateTime
提问by Waheed
I want to convert a nullable DateTime (DateTime?) to a DateTime, but I am getting an error:
我想将可为空的 DateTime ( DateTime?)转换为 a DateTime，但出现错误：
Cannot implicitly convert type 'System.DateTime?' to 'System.DateTime'. An explicit conversion exists (are you missing a cast?)
无法隐式转换类型“System.DateTime?” 到'System.DateTime'。存在显式转换（您是否缺少演员表？）
I have attempted the following:
我尝试了以下方法：
DateTime UpdatedTime = (DateTime)_objHotelPackageOrder.UpdatedDate == null
? DateTime.Now : _objHotelPackageOrder.UpdatedDate;
采纳答案by chills42
You want to use the null-coalescing operator, which is designed for exactly this purpose.
您想使用空合并运算符，它正是为此目的而设计的。
Using it you end up with this code.
使用它你最终得到这个代码。
DateTime UpdatedTime = _objHotelPackageOrder.UpdatedDate ?? DateTime.Now;
回答by adrianbanks
You need to call the Valueproperty of the nullable DateTime. This will return a DateTime.
您需要调用可为空的 DateTime的Value属性。这将返回一个日期时间。
Assuming that UpdatedDateis DateTime?, then this should work:
假设UpdatedDate是DateTime?，那么这应该有效：
DateTime UpdatedTime = (DateTime)_objHotelPackageOrder.UpdatedDate == null ? DateTime.Now : _objHotelPackageOrder.UpdatedDate.Value;To make the code a bit easier to read, you could use the HasValueproperty instead of the nullcheck:
为了使代码更易于阅读，您可以使用HasValue属性而不是null检查：
DateTime UpdatedTime = _objHotelPackageOrder.UpdatedDate.HasValue
? _objHotelPackageOrder.UpdatedDate.Value
: DateTime.Now;
This can be then made even more concise:
这可以变得更加简洁：
DateTime UpdatedTime = _objHotelPackageOrder.UpdatedDate ?? DateTime.Now;
回答by Tim S. Van Haren
Try this:
尝试这个：
DateTime UpdatedTime = (DateTime)_objHotelPackageOrder.UpdatedDate == null ? DateTime.Now : _objHotelPackageOrder.UpdatedDate.Value;
回答by Simon Wilson
How about the following:
以下情况如何：
DateTime UpdatedTime = _objHotelPackageOrder.UpdatedDate.HasValue ? _objHotelPackageOrder.UpdatedDate.value : DateTime.Now;
回答by Valentin Vasilyev
Try this
尝试这个
DateTime UpdatedTime = _objHotelPackageOrder.UpdatedDate ?? DateTime.Now;
回答by Josh
MS already made a method for this, so you dont have to use the null coalescing operator. No difference in functionality, but it is easier for non-experts to get what is happening at a glance.
MS 已经为此制定了一种方法，因此您不必使用空合并运算符。功能上没有区别，但非专家更容易一目了然地了解正在发生的事情。
DateTime updatedTime = _objHotelPackageOrder.UpdatedDate.GetValueOrDefault(DateTime.Now);
回答by Ravi Ram
Here is a snippet I used within a Presenter filling a view with a Nullable Date/Time
这是我在演示者中使用的一个片段，用可空的日期/时间填充视图
memDateLogin = m.memDateLogin ?? DateTime.MinValue
回答by Mateusz Rogulski
You can also try Nullable(T) Properties:
您还可以尝试Nullable(T) 属性：
DateTime UpdatedTime = _objHotelPackageOrder.UpdatedDate.HasValue
? DateTime.Now : _objHotelPackageOrder.UpdatedDate.Value;
回答by Sadiqabbas Hirani
Consider using the following which its far better than the accepted answer
考虑使用以下比公认的答案要好得多的内容
DateTime UpdatedTime = _objHotelPackageOrder.UpdatedDate == null
? DateTime.Now : (DateTime)_objHotelPackageOrder.UpdatedDate;
回答by César León
You can use a simple cast:
您可以使用简单的演员表：
DateTime dtValue = (DateTime) dtNullAbleSource;
As Leandro Tupone said, you have to check if the var is null before
正如 Leandro Tupone 所说，你必须先检查 var 是否为空
