Value, Nothing Yet setting fromDate to Nothing doesn't result in it being set to Nothing but to ' AM', and the following If statement incorrectly executes the filter because startDate is not Nothing.
Where Function i i. Improve this question. ProfK ProfK 46k gold badges silver badges bronze badges. Nothing in VB is closer to being default T in C , rather than null. Note that the two are equivalent for reference types. I personally use New Date as a magic number that means "No Date". Add a comment. Active Oldest Votes. Because it forces the right-hand side's type to be DateTime? As I said in my comment, Nothing can be more akin to C 's default T rather than null : Nothing represents the default value of a data type.
Improve this answer. As you said in your comment as well, "the two are equivalent for reference types", and Nullable Of DateTime is a reference type, but it looks like the cast trick works, thanks. Nullable Of DateTime is a reference type. Since the return type of If has to match the type of one of its expressions, it picked DateTime. It then converts Nothing to a DateTime creating a default DateTime , and only after that point does it consider the assignment.
With VB. NET and EF 6. I think this is an interesting point, though not sure it's exactly answering the original question ;. Where I'm setting a nullable date to null in VB. Value End If. Dim fromDate As Date is even less typing and has the same observable effects. The following example illustrates this. The MinValue and MaxValue properties can be used to ensure that a value lies within the supported range before passing it to a DateTime constructor.
The code in the Example section illustrates this usage. Skip to main content. This browser is no longer supported. Download Microsoft Edge More info. Contents Exit focus mode. Date Time. For example:. Nothing in VB. Net is the equivalent of default T in C : the default value for the given type. MinValue , which obviously does not compile. A more comprehensive explanation can be found on Anthony D. Green's blog. DateTime is a value type, which is why it can't be null.
You can check for it to be equal to DateTime. VB sometimes "helpfully" makes you think it's doing something it's not. When it lets you set a Date to Nothing, it's really setting it to some other value, maybe MinValue. See this question for an extensive discussion of value types vs. Also, on how to check whether a variable is null from Nothing Visual Basic :.
In any programming language, be careful when using Nulls. The example above shows another issue. If you use a type of Nullable, that means that the variables instantiated from that type can hold the value System.
Just a warning You could create a separate class containing a value type. An object created from such a class would be a reference type, which could be assigned Nothing. An example:. Then you could pick and choose overridables to make it do what you need. Lot of work - but if you really need it, you can do it. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams?
Collectives on Stack Overflow. Learn more. Why can't I check if a 'DateTime' is 'Nothing'? Ask Question. Asked 10 years, 8 months ago.
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