Oops, the "code" below should be defining a struct, not a class (i.e. "struct NullableDateTime).
Cheers, Blake > -----Original Message----- > From: Blake Ryan [mailto:[EMAIL PROTECTED]] > Sent: 13 May 2002 11:20 > To: [EMAIL PROTECTED] > Subject: Re: [DOTNET] DateTime, C# and null > > > 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. > KSS Ltd A division of Knowledge Support Systems Group plc Seventh Floor St James's Buildings 79 Oxford Street Manchester M1 6SS England Company Registration Number 2800886 (Limited) 3449594 (plc) Tel: +44 (0) 161 228 0040 Fax: +44 (0) 161 236 6305 mailto:[EMAIL PROTECTED] http://www.kssg.com The information in this Internet email is confidential and may be legally privileged. It is intended solely for the addressee(s). Access to this Internet email by anyone else is unauthorised. If you are not the intended recipient, any disclosure, copying, distribution or any action taken or omitted to be taken in reliance on it, is prohibited and may be unlawful. When addressed to our clients any opinions or advice contained in this Internet email are subject to the terms and conditions expressed in the governing engagement letter or contract. This email message and any attached files have been scanned for the presence of computer viruses. However you are advised that you open any attachments at your own risk. You can read messages from the DOTNET archive, unsubscribe from DOTNET, or subscribe to other DevelopMentor lists at http://discuss.develop.com. You can read messages from the DOTNET archive, unsubscribe from DOTNET, or subscribe to other DevelopMentor lists at http://discuss.develop.com.
