C# linq issue

Sie Ste

I have a C# 2010 application that I would like to add the following lines of code:
eDataContext rData = new eDataContext();
DateTime complete_date = (DateTime)(from a in rData.cust
where a.PkID == pkId
select a.Complete_Date).FirstOrDefault();
if (complete_date != null)

The linq statement where DateTime complete_date is assigned a value works.
However when I try to executed the line of code
(complete_date != null),

the program has a problem on this line of code. I found this out by stepping though the
code.

Thus can you tell me why the
"if (complete_date != null)" line of code is having a problem? Also can you tell me what to
do to solve the problem?

3 Replies

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Vulpes14y ago
Accepted answer
If for some reason you don't want to use a nullable DateTime, then you can check against the default value for an 'ordinary' DateTime which is 12.00 midnight on January 1, 0001 and therefore very unlikely to be used in practice.

The FirstOrDefault() extension method will return this value if there are no results in the query:

if (complete_date != default(DateTime))

Incidentally, casting to DateTime in your query is unnecessary as the returned value is a DateTime already.
Sukesh Marla14y ago
agree shivanand
Shivanand Arur14y ago
Sie Ste - A DateTime value can never be null since it is a struct, but a Nullable DateTime can be null...

For more information on Nullable Datetime check out this site...
http://www.dotnetperls.com/nullable-datetime

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