vb.net 具有现在（日期）默认值的可选参数
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Optional Parameter with now (Date) default value
提问by bgs
How to assign the default Date Time ( Now ) value for optional parameter.
如何为可选参数分配默认日期时间 ( Now ) 值。
When assigning the now object to optional parameter below error is raised
将 now 对象分配给以下错误的可选参数时
Constant expression is required
Code:
代码：
Public Sub ReminderMail(Optional ByVal ReminderMailDate As DateTime = Now)
// Code Block
End Sub
回答by
Try this :
尝试这个 ：
Public Sub ReminderMail(Optional ByVal ReminderMailDate As DateTime = Nothing)
If ReminderMailDate = Nothing Then ReminderMailDate = Now
// Code Block
End Sub
回答by Damien_The_Unbeliever
Instead of using an optional parameter, you might want to consider offering two overloads of your Sub:
您可能需要考虑提供两个重载，而不是使用可选参数Sub：
Public Sub ReminderMail()
ReminderMail(DateTime.Now)
End Sub
Public Sub ReminderMail(ByVal ReminderMailDate As DateTime)
// Code Block
End Sub
Which from a caller's perspective, operates quite similarly.
从调用者的角度来看，其操作非常相似。
