LINQ to Entities for subtracting 2 dates
I am trying to determine the number of days between 2 dates using LINQ with Entity Framework. It is telling me that it does not recognize Subtract on the System.TimeSpan class
Here is my where portion of the LINQ query.
where ((DateTime.Now.Subtract(vid.CreatedDate).TotalDays < maxAgeInDays))
Here is the error I receive in the VS.NET debugger
{"LINQ to Entities does not recognize the method 'System.TimeSpan Subtract(System.DateTime)' method, and this method cannot be translated into a store expression."}
Am I doing something wrong or is there a better way to get the number of days between 2 DateTimes in the entity framework?
thanks Michael
The accepted answer is better in this case, but for reference you can use the EntityFunctions
class to perform operations on dates, among other things.
where (vid.CreatedDate >= EntityFunctions.AddDays(DateTime.Now, -maxAgeInDay))
Here is how I got it to work
I defined a datetime variable that represents the oldest date
DateTime oldestDate = DateTime.Now.Subtract(new TimeSpan(maxAgeInDays, 0, 0, 0, 0));
...
then I modified the where portion of the LINQ query
where (vid.CreatedDate >= oldestDate )
worked like a charm - thanks Micah for getting me to think about the expression tree
You can also use System.Data.Objects.EntityFucntions
:
currentDate = DateTime.Now;
...
where EntityFunctions.DiffDays(currentDate, vid.CreatedDate) < maxAgeIdDays
All functions from EntityFunctions
are only for Linq-to-entities and are mapped to SQL functions.