DateTime Null

[shapper]

Hello,

I have the following:

DateTime c = database.Posts.Max(b =b.CreatedAt).Value;

b.CreatedAt is of type "DateTime?"

The problem is when database.Posts is empty. I get an error:
Nullable object must have a value.

I understand that I get a null value but I am not able to apply ??
because it does not allow me.

How can I solve this?

Thanks,
Miguel

[Peter Duniho]

On Sun, 19 Oct 2008 14:03:00 -0700, shapper <md*****@gmail.comwrote:

Hello,

I have the following:

DateTime c = database.Posts.Max(b =b.CreatedAt).Value;

b.CreatedAt is of type "DateTime?"

The problem is when database.Posts is empty. I get an error:
Nullable object must have a value.

I understand that I get a null value but I am not able to apply ??
because it does not allow me.

How can I solve this?

Can you be more explicit about what you mean by "it does not allow me"?
You didn't post any code that tries to use the null coalescing operator
(??). There's not any particular reason why "it" (the compiler, I presume
you mean) should not "allow" you to use it.

If you can post the code that you think should work but doesn't, we can
help change that to code that does work.

Pete

[shapper]

On Oct 19, 10:33*pm, "Peter Duniho" <[e-mail]>
wrote:

On Sun, 19 Oct 2008 14:03:00 -0700, shapper <[e-mail]:

Hello,

I have the following:

DateTime c = database.Posts.Max(b =b.CreatedAt).Value;

b.CreatedAt is of type "DateTime?"

The problem is when database.Posts is empty. I get an error:
Nullable object must have a value.

I understand that I get a null value but I am not able to apply ??
because it does not allow me.

How can I solve this?

Can you be more explicit about what you mean by "it does not allow me"? *
You didn't post any code that tries to use the null coalescing operator *
(??). *There's not any particular reason why "it" (the compiler, I presume *
you mean) should not "allow" you to use it.

If you can post the code that you think should work but doesn't, we can *
help change that to code that does work.

Pete

Sure ... Sorry. I tried:

DateTime c = database.Boxes.Max(b =b.CreatedAt ?? DateTime.UtcNow);

Which seemed logic to me but I get:
The null value cannot be assigned to a member with type
System.DateTime which is a non-nullable value type.

I also tried:
DateTime c = database.Boxes.Max(b =b.CreatedAt).Value ??
DateTime.UtcNow;

But this one does not even compile and I get:
Operator '??' cannot be applied to operands of type 'System.DateTime'
and 'System.DateTime

Thanks,
Miguel

[Peter Duniho]

On Sun, 19 Oct 2008 14:43:30 -0700, shapper <md*****@gmail.comwrote:

Sure ... Sorry. I tried:

DateTime c = database.Boxes.Max(b =b.CreatedAt ?? DateTime.UtcNow);

Which seemed logic to me but I get:
The null value cannot be assigned to a member with type
System.DateTime which is a non-nullable value type.

Ah. Yes, it would do that when the database is empty. But, if you move
the coalescing operator out of the lambda expression, I think it should be
okay:

DateTime c = database.Boxes.Max(b =b.CreatedAt) ?? DateTime.UtcNow;

Note that that's subtly different from what you did try:

I also tried:
DateTime c = database.Boxes.Max(b =b.CreatedAt).Value ??
DateTime.UtcNow;

You can only use nullable types with the coalescing operator. The
Nullable<DateTime>.Value property is a non-nullable value type and so is
an illegal operand for the operator.

Without a true concise-but-complete code sample, it's difficult to know
for sure what will or won't work. But I'm pretty sure the above should
solve your problem.

Pete

[shapper]

On Oct 20, 12:20*am, "Peter Duniho" <[e-mail]>
wrote:

On Sun, 19 Oct 2008 14:43:30 -0700, shapper <[e-mail]:

Sure ... Sorry. I tried:

DateTime c = database.Boxes.Max(b =b.CreatedAt ?? DateTime.UtcNow);

Which seemed logic to me but I get:
The null value cannot be assigned to a member with type
System.DateTime which is a non-nullable value type.

Ah. *Yes, it would do that when the database is empty. *But, if you move *
the coalescing operator out of the lambda expression, I think it should be *
okay:

* * *DateTime c = database.Boxes.Max(b =b.CreatedAt) ?? DateTime.UtcNow;

Note that that's subtly different from what you did try:

I also tried:
DateTime c = database.Boxes.Max(b =b.CreatedAt).Value ??
DateTime.UtcNow;

You can only use nullable types with the coalescing operator. *The *
Nullable<DateTime>.Value property is a non-nullable value type and so is *
an illegal operand for the operator.

Without a true concise-but-complete code sample, it's difficult to know *
for sure what will or won't work. *But I'm pretty sure the above should*
solve your problem.

Pete

Thank You Pete. I didn't know that about value ... I though it would
still be a nullable DateTime.