[英]C# - DateTime.TryParse issue - why doesn't it like my string representation of my date?
Here's my code: 这是我的代码:
DateTime Dob = Convert.ToDateTime("1/1/1800");
DateTime Dod = Convert.ToDateTime("1/1/1800");
if (!DateTime.TryParse(p.birthday, out Dob) && !DateTime.TryParse(p.deathday, out Dod))
{
// handle error
}
p.birthday
is: p.birthday
是:
p.deathday
is: p.deathday
是:
When the .TryParse()
code hits, my DateTime
object for Dob is: 当
.TryParse()
代码命中时,我的Dob的DateTime
对象是:
And the DateTime
object for Dod is: 而Dod的
DateTime
对象是:
QUESTION : Why is Dod
still "1-1-1800" (the initial value I assigned), but Dob
is set correctly? 问题 :为什么
Dod
仍然是“1-1-1800”(我指定的初始值),但Dob
设置正确? Is there something about the Dod value of "2007-02-28" that it doesn't like? 关于“2007-02-28”的Dod值有什么不喜欢的吗?
DateTime.TryParse(p.birthday, out Dob)
successfully converts the string
to DateTime
, so it returns true. DateTime.TryParse(p.birthday, out Dob)
成功将string
转换为DateTime
,因此返回true。 You invert this with !
你用它来反转
!
, giving false. 给予假。
When the execution gets to the &&
operator, it sees the first operand is already false
, so doesn't bother executing the second operand. 当执行到达
&&
运算符时,它看到第一个操作数已经为false
,因此不会打扰执行第二个操作数。
You could either execute both beforehand, or use the non-shortcut AND operator, &
. 您既可以预先执行,也可以使用非快捷方式AND运算符
&
。
Edit: Or 编辑:或
if (!(DateTime.TryParse(p.birthday, out Dob) || DateTime.TryParse(p.deathday, out Dod)))
{
...
}
The reason is that its executing !(DateTime.TryParse(p.birthday, out Dob) and returning false. Therefore !DateTime.TryParse(p.deathday, out Dod) is not executed. 原因是它正在执行!(DateTime.TryParse(p.birthday,out Dob)并返回false。因此!DateTime.TryParse(p.deathday,out Dod)不会被执行。
According to 根据
http://msdn.microsoft.com/en-us/library/2a723cdk.aspx
x && y
if x is false, y is not evaluated, because the result of the
AND operation is false no matter what the value of y is. This is known as
"short-circuit" evaluation.
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