DateTime

[shapper]

Hello,

I defined a DateTime variable:

Dim dt As New DateTime

How can I check if it is empty?

Basically I want to check if it was given to it a DateTime value or
not.

Thanks,

Miguel

 

[Karl Seguin [MVP]]

You can't. DataTime is a ValueType..it's stored on the stack and always has
a default value (like an int).

a hack solution is to assign it a value that'll never get used:

dim dt as datetime = datetime.MinValue

but that's a hack.

In 2.0, you can use a nullable type...

dim dt as Nullable(Of DateTime)

which you can then compare against nothing and do other stuff...still not
great, but the best solution.

Karl

 

[Mark Rae]

I defined a DateTime variable:

Dim dt As New DateTime

How can I check if it is empty?

Basically I want to check if it was given to it a DateTime value or
not.

You can't, at least, not 100% reliably. When a DateTime variable is
instantiated, its default value is DateTime.MinValue, not null. You could
check whether dt = DateTime.MinValue, but it will never be null (or empty)
because it is a value type.

..NET 2 introduced the concept of nullable datatypes e.g. DateTime? as well
as DateTime etc. However, when a DateTime? variable is instantiated, it also
has a default value of DateTime.MinValue - you can, though explicitly set a
DateTime? variable to null, which you can't do with a DateTime variable...

 

[Mark Rae]

In 2.0, you can use a nullable type...

dim dt as Nullable(Of DateTime)

Yes, but you will have to explicitly set it to Nothing first, won't you...?

 

[Karl Seguin [MVP]]

not in C#..maybe vb.net..dunno.

Karl

 

[Mark Rae]

not in C#..maybe vb.net..dunno.

Oh sure - not a problem at all in C#...

DateTime? dt = null;