Ignoring accents in SQL Server using LINQ to SQL - sql-server

Question

How can I ignore accents (like ´, `, ~) in queries made to a SQL Server database using LINQ to SQL?
UPDATE:
Still haven't figured out how to do it in LINQ (or even if it's possible) but I managed to change the database to solve this issue.
Just had to change the collation on the fields I wanted to search on. The collation I had was:
SQL_Latin1_General_CP1_CI_AS
The CI stans for "Case Insensitive" and AS for "Accent Sensitive". Just had to change the AS to AI to make it "Accent Insensitive".
The SQL statement is this:
ALTER TABLE table_name ALTER COLUMN column_name column_type COLLATE collation_type

Answer 1

In SQL queries (Sql Server 2000+, as I recall), you do this by doing something like select MyString, MyId from MyTable where MyString collate Latin1_General_CI_AI ='aaaa'.
I'm not sure if this is possible in Linq, but someone more cozy with Linq can probably translate.
If you are ok with sorting and select/where queries ALWAYS ignoring accents, you can alter the table to specify the same collation on the field(s) with which you are concerned.

Answer 2

See the following answer:
LINQ Where Ignore Accentuation and Case
Basically you need to alter the field type in SQL Server, e.g.
ALTER TABLE People ALTER COLUMN Name [varchar](100) COLLATE SQL_Latin1_General_CP1_CI_AI
There does not seem to be a way to do this using LINQ, apart from calling a custom method to remove diacritics (which would not be performant).

Answer 3

LINQ to SQL doesn't have any specific functionality for setting the collation used for a query and so it will always use the database default.

Answer 4

It seems that there is a way to ignore the collation differences in Linq to SQL by using t-sql functions:
CREATE FUNCTION [dbo].[func_ConcatWithoutCollation]
(
#param1 varchar(2000),
#param2 varchar(2000)
)
RETURNS varchar(4000)
AS
BEGIN
IF (#param1 IS NULL) SET #param1 = ''
IF (#param2 IS NULL) SET #param2 = ''
RETURN #param1 COLLATE Latin1_General_CS_AS + #param2 COLLATE Latin1_General_CS_AS
END
to get this function in linq to sql, there is a switch for SqlMetal: /functions.
Example:
"%ProgramFiles%\Microsoft SDKs\Windows\v7.0A\Bin\SqlMetal.exe" /server:. /database:NameOfDatabase /pluralize /code:ContextGenerated.cs /sprocs /views /functions
Use this function in Linq to sql like this:
from s in context.Services
where context.Func_ConcatWithoutCollation(s.Description, s.Email) == "whatever"
select s
It helped me, maybe somebody finds this useful too.

Answer 5

A solution could be create an SQL Function to remove the diacritics, by applying to the input string the collation SQL_Latin1_General_CP1253_CI_AI, like so:
CREATE FUNCTION [dbo].[RemoveDiacritics] (
#input varchar(max)
) RETURNS varchar(max)
AS BEGIN
DECLARE #result VARCHAR(max);
select #result = #input collate SQL_Latin1_General_CP1253_CI_AI
return #result
END
Then you could add it in the DB context (in this case ApplicationDbContext) by mapping it with the attribute DbFunction:
public class ApplicationDbContext : IdentityDbContext<CustomIdentityUser>
{
[DbFunction("RemoveDiacritics", "dbo")]
public static string RemoveDiacritics(string input)
{
throw new NotImplementedException("This method can only be used with LINQ.");
}
public ApplicationDbContext(DbContextOptions<ApplicationDbContext> options)
: base(options)
{
}
}
And finally use it in LINQ query, for example (linq-to-entities):
var query = await db.Users.Where(a => ApplicationDbContext.RemoveDiacritics(a.Name).Contains(ApplicationDbContext.RemoveDiacritics(filter))).tolListAsync();