Linq-To-Sql convert string to date with specific format

Question

I have a date stored as a string in a not so good format (dd-MM-yyyy). The SQL server cannot automatically convert this into a date, at least not with the settings that are on it, but with a little help it fixes it. The following SQL statement works perfectly:

select * from table
where convert(date,myValue,105) < GETDATE()

Problem I have is, how do I do this in LINQ? I tried different things manually and I tested Linqer to generate LINQ from my SQL. This is what Linqer gives me:

from table in db.table
where
  Convert.ToDateTime(myValue) < DateTime.Now
select new {
  ...
}

Problem is, when I run the statement above I get:

The conversion of a nvarchar data type to a datetime data type resulted in an out-of-range value.

Probably because it drops the 105 parameter to the convert method. I've tried different parse methods (Parse, ParseExact and Convert.ToDateTime with an IFormatProvider) but all those give me errors that are more or less like:

Method 'System.DateTime ParseExact(System.String, System.String, System.IFormatProvider)' has no supported translation to SQL.

So my question is, is there a good way to convert a date with an "odd" dateformat in Linq so that I will get working T-SQL? I already have a "working" solution, but I would like to know if there's any way to get Linq to interpret this in a nice way?

Answer 1

Although this is not the best practice but if it works then so be with it, I suggest you create a View in your table

  CREATE VIEW view_table 
  AS 
  select tbl_id, 
         convert(date,myValue,105) as myDate
  from table

so then from your linq

     from table in db.view_table
        where
        Convert.ToDateTime(myDate) < DateTime.Now
   select new {
      ...
   }

because the column myValue is already converted to 105 format.

Answer 2

It might be better to convert them locally with using AsEnumerable and DateTime.ParseExact .

from table in db.table.AsEnumerable()
where
  DateTime.ParseExact(myValue, "dd-MM-yyyy", CultureInfo.InvariantCulture) < DateTime.Now
select new {
  ...
}

Answer 3

You should be able to parse out the parts manually and build a new DateTime

from table in db.table
let myValue = new DateTime(Convert.ToInt32(yourdate.Substring(6,4)),Convert.ToInt32(yourdate.Substring(3,2)),Convert.ToInt32(yourdate.Substring(0,2)))
where
  myValue < DateTime.Now

select new { ... }

yourdate is a date in string dd-MM-yyyy format