C# compare sql datetime to null

Question

I'm creating something in ASP.NET MVC 4 and in one of my tables there is a field of type datetime. This field is defaulted to null until it is updated. I am trying select from this table the rows that have this field as null but my LINQ query always returns nothing. This is my query.

from m in this._db.MessageReadStates
where m.UserName == name
      && m.ReadDate == null
select m

I new to C# so is there a correct way to check for null?

What is the .NET type of ReadDate? DateTime or DateTime? — Joe
– Joe, Commented Apr 30, 2012 at 18:31
looks like this post solves ur problem stackoverflow.com/questions/2509044/linq-query-null-date — Paras
– Paras, Commented Apr 30, 2012 at 18:31

zimdanen · Accepted Answer · 2012-04-30 18:38:10Z

6

You want to check the HasValue property of the Nullable<DateTime> type:

&& !m.ReadDate.HasValue

edited Apr 30, 2012 at 18:38

answered Apr 30, 2012 at 18:29

zimdanen

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2 Comments

Declan Cook Over a year ago

Results in this warning - The given expression is never of the provided ('System.DBNull')

zimdanen Over a year ago

Edited in response to your clarification of the type in the question comments.

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