LINQ: concatenate multiple int properties into a string - linq

Question

I have an object with two different integer properties in it, and I'm trying to get a a new object in Linq to Entities, combining two integer properties from the same object as concatenated strings, as follows
List<DateRange> collection = (from d in context.dates
select new DateRange
{
DateString = from s in context.Seasons
where s.SeasonID = d.DateID
select string.Format("{0} - {1}", s.StartYear, s.EndYear) }
).ToList<DateRange>();
The string concatenation of the years will not compile.

Answer 1

This will work in LINQ to Objects, provided that each object in objects is a class or struct containing "Number1" and "Number2" fields or properties:
var results = from o in objects
select string.Format("{0} - {1}", o.Number1, o.Number2);
(However, your original should work, as well....)

Answer 2

Assuming you are connecting to a database via LINQ to SQL/Entities, then the String.Format call will likely fail, as with those providers, the select clause is executed within the database. Not everything can be translated from C# into SQL.
To convert your database results into a string like you want to, the following should work:
var temp = (
from d in context.dates
from s in context.Seasons
where s.SeasonID == d.DateID
select new { s.StartYear, s.EndYear }
).ToList(); // Execute query against database now, before converting date parts to a string
var temp2 =
from t in temp
select new DateRange
{
DateString = t.StartYear + " - " + t.EndYear
};
List<DateRange> collection = temp2.ToList();
EDIT:
I had an additional thought. The String.Format call is most likely the problem. I am not sure if it would work or not, but what about a plain-jane concat:
List<DateRange> collection =
(from d in context.dates
select new DateRange
{
DateString = from s in context.Seasons
where s.SeasonID = d.DateID
select s.StartYear + " - " + s.EndYear
}
).ToList<DateRange>();

Answer 3

Your original code works if you really want what you wrote. However, if your really want to get from
var objects = new MyObject[]{
new MyObject {Int1 = 1, Int2 = 2},
new MyObject {Int1 = 3, Int2 = 4}};
something like 1 - 2 - 3 - 4 you can write
var strings = objects.Select(o = > string.Format("{0} - {1}", o.Int1, o.Int2).ToArray();
var output = string.Join(" - ", strings);

Answer 4

using System.Data.Objects.SqlClient;
:
:
List<DateRange> collection = (from d in context.dates
select new DateRange
{
DateString = from s in context.Seasons
where s.SeasonID = d.DateID
select SqlFunctions.StringConvert((double)s.StartYear) + " - " +
SqlFunctions.StringConvert((double)s.EndYear)
}).ToList<DateRange>();
The StringConvert method gets converted into the proper conversion function when the LINQ statement is converted to SQL for execution on the server.