How do I perform Date Comparison in EF query?

Question

Please help. I am trying to figure out how to use DATE or DATETIME for comparison in a linq query.

Example: If I wanted all Employee names for those who started before today, I would do something like this in SQL:

SELECT EmployeeNameColumn
FROM EmployeeTable
WHERE StartDateColumn.Date <= GETDATE() //Today

But what about linq?

DateTime startDT = //Today

var EmployeeName =  
from e in db.employee
where e.StartDateColumn <= startDT

The above WHERE doesn't work:

Exception Details: System.NotSupportedException: The specified type member 'Date' is not supported in LINQ to Entities. Only initializers, entity members, and entity navigation properties are supported.

user_895724 · Answer

Use the class DbFunctions for trimming the time portion.

using System.Data.Entity;

var bla = (from log in context.Contacts
           where DbFunctions.TruncateTime(log.ModifiedDate) 
                              ==  DbFunctions.TruncateTime(today.Date)
           select log).FirstOrDefault();

Source: http://social.msdn.microsoft.com/Forums/en-US/csharpgeneral/thread/84d4e18b-7545-419b-9826-53ff1a0e2a62/

Jason_45914 · Answer

That should work. Are you sure that there isn't another part of the query that triggered the exception? I have several instances of queries of the form

var query = from e in db.MyTable
            where e.AsOfDate <= DateTime.Now.Date
            select e;

in my code.

user_86611 · Answer

It may be due to the date in the database being nullable. Try this:

var EmployeeName =
from e in db.employee
where e.StartDateColumn.Value <= startDT

Admin · Answer

You can not use .Date

If you would like to check for today you can create a datetime with no time

DateTime myDate = new DateTime(DateTime.Now.Year, DateTime.Now.Month, DateTime.Now.Day);
var e = (from mds in myEntities.Table
         where mds.CreateDateTime >= myDate
         select mds).FirstOrDefault();

user_133802 · Answer

I'm curious to the error message saying 'Date', when you're passing a 'DateTime'. Could it be that 'StartDateColumn' is actually a 'Date', rather than a 'DateTime' in the database? That might mess up the comparison...

user_558907 · Answer

I am using a LinqDataSource and I had problems getting my query with a Date Comparison in it to execute without errors. The answer is to use the WhereAddParameters function and add the test value as a strongly typed parameter.

See the example below where I am matching a groupid and checking to see if the StopDate in my record is greater that or equal to a Date/Time stamp of now.

I am using this code fragment currently and it works like a charm.

LinqCampaigns.WhereParameters.Add("StopDate", System.Data.DbType.Date, DateTime.Now.ToString())
LinqCampaigns.Where = "GroupId = " & myGrp & " &&  " & "StopDate >= @StopDate"

Works like a charm....

How do I perform Date Comparison in EF query?

11 Answers