3 solutions come to mind:
(a) use DateTime.MinValue to represent null
(b) box the DateTime value (i.e. pass it as an object)
(c) write a NullableDateTime class
The 3rd is the only really "proper" way to do it, as it doesn't assume
anything about the DateTime value (as (a) does) or prevent static type
checking (as (b) does). I'd suggest a class like the following:
class NullableDateTime
{
public NullableDateTime( DateTime value );
// Throws if object is not null or DateTime
public NullableDateTime( object value );
public static implicit operator NullableDateTime( DateTime value );
public static NullableDateTime Null
{
get;
}
public bool isNull
{
get;
}
// Throws InvalidOperationException if null
public DateTime Value
{
get;
}
// Returns null if null
public object ObjValue
{
get;
}
// Returns DBNull.Value if null
public object DbValue
{
get;
}
}
One advantage of this is that the implicit conversion operator allows you to
pass a DateTime without explicit casting/conversion. You could argue that
the Value property could be implemented as an explicit cast (i.e. public
static explicit operator DateTime( NullableDateTime value )), but throwing
an InvalidOperation exception from a "cast" operation is not really
desirable.
Hope this helps.
Cheers,
Blake
> -----Original Message-----
> From: Yves Reynhout [mailto:[EMAIL PROTECTED]]
> Sent: 13 May 2002 11:03
> To: [EMAIL PROTECTED]
> Subject: [DOTNET] DateTime, C# and null
>
>
> Hi,
>
> what if I had a webservice method which takes a DateTime
> parameter and I
> want to be able to NOT specify this parameter (i.e. pass null
> as a value).
> One might suggest to use overloading (and run in to the
> trouble of having
> to give each webservice method a unique name(in the wsdl),
> but let's not
> delve into that one), but frankly that's not what I want.
>
> The same question arises (how do I properly handle null with
> valuetypes
> such as int, datetime, ...) when creating [business] objects. Am I
> obligated to revert to a homegrown datetime class, int class,
> etc... just
> to be able to handle the null situation? What is common
> practice? How can
> this problem be tackled in an OO-minded fashion?
>
> Awaiting your responses...
>
> You can read messages from the DOTNET archive, unsubscribe
> from DOTNET, or
> subscribe to other DevelopMentor lists at http://discuss.develop.com.
>
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