Using int.parse(string) in linq search doesn't work

Question

I'm using LINQ search in C#. One of my searches require converting a string to an int . When I try to use int.parse() or convert.toInt32() , it displays an error (not recognized in LINQ)

for example:

var google = from p in ctx.dates
       where int.Parse(p.effDate) < 20101212 && int.Parse(p.effDate) > 20121212
           select p;

as you can see I have a string that contains my date in yyyymmdd format and I want to convert it to an integer so I can search between those date.

Answer 1

The yyyyMMdd format has a nice property that the lexicographical ordering is the same as the chronological ordering so you can use string comparisons:

var google = from p in ctx.dates
             where p.effDate.CompareTo("20121212") < 0
             && p.effDate.CompareTo("20101212") > 0
             select p;

Answer 2

As first you can't compare dates by just converting them to int, because it will fail in most cases. Parse your strings using DateTime Parse or ParseExact and compare them.

Answer 3

That's because int.Parse is a client call, the Linq provider doesn't know how to map that to a database function.

Since the string is in an easily sorted format, you can use where p.effDate < "20101212" && p.effDate > "20121212" .

A better approach would be to change the database to store the dates in date columns not char or varchar columns.

Answer 4

finaly i've found a decent answer :

 google = from p in ctx.dates
 where p.effDate.CompareTo(picker1) > 0 && p.effDate.CompareTo(picker2) <0 
select p; 

picker1 and picker2 are both strings in "yyyymmdd" thank you all for helping me