c# - Comparing nullable DateTime?

Question

Looking for a better way to compare a nullable date time than the following:

Any suggestions?

// myobject.ExpireDatetime is of DateTime?
//
if (!myobject.ExpireDateTime.IsNull() && DateTime.Compare((DateTime)myobject.ExpireDateTime, DateTime.Now.ToUniversalTime()) < 0)
{ //error! }    

Edited: Sorry for confusion...myobject.ExpireDatetime is of type DateTime.

question from:https://stackoverflow.com/questions/13673117/comparing-nullable-datetime

Answer 1

Your question is not quite clear to me, but if we have

DateTime? ExpireDateTime;  // could be a variable or a property

it's OK to say just

if (ExpireDateTime < DateTime.UtcNow)
{
  ...
}

This will be OK if ExpireDateTime is null (HasValue is false). Some inexperienced developers will struggle to understand lifted operators, so to make it more clear, you could write

if (ExpireDateTime < (DateTime?)DateTime.UtcNow)
{
  ...
}

It's the same, but easier to read and understand.

Never write .Value if the nullable might be null, of course. You will get an InvalidOperationException "Nullable object must have a value" if you do so.