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Create SQL query with WHERE .. IN condition using list of integer

I am not an expert of SQL and what I am trying to achieve is the following.
I have a list of integers called PersonIds. First of all I need to transform this list of integers to a list of strings. Why? Because as far as I have understood for the WHERE .. IN condition in SQL this is the kind of variable I need to feed to the query.
Then I need to modify the list of strings in order to prevent SQL injection and therefore inserting # before every Id of the list.
At last I create the query and feed the list I just created.
What I tried to do is:
var listIds = string.Join(",#", PersonIds, 0, PersonIds.Count()));
var query = $"DELETE FROM PersonTable WHERE PersonId IN (#{listIds})";
There is something I am doing wrong. To recap I need to steps:
preparing a list (including mechanism to avoid SQL injection) that I need to feed to the query
create the query using as argument the list I created
Thanks in advance!

Perhaps the simplest way is to add some Dapper:
List<int> listIds = ...
connection.Execute("DELETE FROM PersonTable WHERE PersonId IN #listIds",
new { listIds });
Dapper does all the hard work of figuring out how to parameterize that, while still staying almost close to regular TSQL. You can also optionally enable string_split usage if you're using recent versions of SQL Server, to minimize the parameter count and query-plan cache size.
Note that the missing parentheses is deliberate and intentional - dapper treats this slightly differently to the regular IN (#foo, #bar) syntax.

LINQ: Translating a SQL WITH clause to LINQ and Entity Framework

I have an app using Entity Framework. I want to add a tree view listing products, grouped by their categories. I have an old SQL query that will grab all of the products and categories and arrange them into parent nodes and children. I am trying to translate it into LINQ that uses the EF. But the SQL has a WITH sub-query that I am not familiar with using. I have tried using Linqer and LinqPad to sort it out, but they choke on the WITH clause and I am not sure how to fix it. Is this sort of thing possible in LINQ?
Here is the query:
declare #id int
set #id=0
WITH ChildIDs(id,parentid,type,ChildLevel) AS
(
SELECT id,parentid,type,0 AS ChildLevel
FROM dbo.brooks_product
WHERE id = #id
UNION ALL
SELECT e.id,e.parentid,e.type,ChildLevel + 1
FROM dbo.brooks_product AS e
INNER JOIN ChildIDs AS d
ON e.parentid = d.id
WHERE showitem='yes' AND tribflag=1
)
SELECT ID,parentid,type,ChildLevel
FROM ChildIDs
WHERE type in('product','productchild','productgroup','menu')
ORDER BY ChildLevel, type
OPTION (MAXRECURSION 10);
When I run the query, I get data that looks like this (a few thousand rows, truncated here):
ID.....parentid.....type.....ChildLevel
35429..0............menu.....1
49205..0............menu.....1
49206..49205........menu.....2
169999.49206........product..3
160531.169999.......productchild..4
and so on.

The WITH block is a Common Table Expression, and in this case is used to create a recursive query.
This will be VERY difficult in Linq as Linq doesn't play well with recursion. If you need all of the data on one result set that a Stored Procedure would be easier. Another option is to do the recursion in C# (not in Linq but a recursive function) and do multiple round-trips. The performance will not be as good but if you result set is small it may not make much difference (and you will get a better object model).

You may be able to solve this using LINQ to Entities, but it is non-trivial and I suspect it will be very time consuming.
In situations like this, you may prefer to build a SQL View or Table-Valued Function that returns the results for which you're looking. Then import that View or Table-Valued Function into your EF model and you can pull data directly from it using LINQ.
Querying the View in LINQ is no different than querying a table.
To get data from a Table-Valued Function in LINQ, you pass the function's parameters in after the name of the function, like so:
var query = from tvf in _db.MyTableValuedFunction(parameters)
select tvf;
EDIT
As suggested by #thepirat000, Table-Valued Function support is not available in Entity Framework versions prior to version 5. In order to use this functionality, EF must be running with .NET 4.5 or higher.

At the end of the day, I could not get this to work. I ended up writing out a SQL query dynamically and sending that straight to the database. It works fine, and I am not relying on any direct user input so there is no chance of SQL injection. But it seems so old school! For the rest of my program I am using EF and LINQ.
Thanks for the replies!

Can I easily evaluate many IQueryables in a single database call using Entity Framework?

Suppose I have a collection (of arbitrary size) of IQueryable<MyEntity> (all for the same MyEntity type). Each individual query has successfully been dynamically built to encapsulate various pieces of business logic into a form that can be evaluated in a single database trip. Is there any way I can now have all these IQueryables executed in a single round-trip to the database?
For example (simplified; my actual queries are more complex!), if I had
ObjectContext context = ...;
var myQueries = new[] {
context.Widgets.Where(w => w.Price > 500),
context.Widgets.Where(w => w.Colour == 5),
context.Widgets.Where(w => w.Supplier.Name.StartsWith("Foo"))
};
I would like to have EF perform the translation of each query (which it can do indivudually), then in one database visit, execute
SELECT * FROM Widget WHERE Price > 500
SELECT * FROM Widget WHERE Colour = 5
SELECT W.* FROM Widget
INNER JOIN SUpplier ON Widget.SupplierId = Supplier.Id
WHERE Supplier.Name LIKE 'Foo%'
then convert each result set into an IEnumerable<Widget>, updating the ObjectContext in the usual way.
I've seen various posts about dealing with multiple result sets from a stored procedure, but this is slightly different (not least because I don't know at compile time how many results sets there are going to be). Is there an easy way, or do I have to use something along the lines of Does the Entity Framework support the ability to have a single stored procedure that returns multiple result sets??

No. EF deosn't have query batching (future queries). One queryable is one database roundtrip. As a workaround you can try to play with it and for example use:
string sql = ((ObjectQuery<Widget>)context.Widgets.Where(...)).ToTraceString();
to get SQL of the query and build your own custom command from all SQLs to be executed. After that you can use similar approach as with stored procedures to translate results.
Unless you really need to have each query executed separately you can also union them to single query:
context.Widgets.Where(...).Union(context.Widgets.Where(...));
This will result in UNION. If you need just UNION ALL you can use Concat method instead.

It might be late answer, hopefully it would help some one else with the same issue.
There is Entity Framework Extended Library on NuGet which provides the future queries feature (among others). I played a bit with it and it looks promising.
You can find more information here.

Linq query nhibernate; not supported exception

I'm fairly new to nHibernate having come from an EF background and I'm struggling with the following query :
_patientSearchResultModel = (from patient in _patientRepository.Query(patientSearch.BuildPatientSpecification())
join admission in _admissionRepository.Query(patientSearch.BuildAdmissionSpecification())
on patient.Id equals admission.Patient.Id
orderby admission.AdmissionDate
select new PatientSearchResultModel(patient.Id,
admission.Id,
false,
_phaseTypeMapper.GetPhaseTypeModel(admission.PhaseType),
patient.Last, patient.First,
admission.InPatientLocation,
admission.AdmissionDate,
admission.DischargeDate,
admission.RRI,
null,
admission.CompletionStatus,
admission.FollowupStatus)).ToList();
The intent of this query is to allow users to filter the two queries on parameters built up using the two Build???Specification functions and return the resultset. There could be many admission records and I would only like one PatientSearchResultModel per patient object, with the admission object being the newest one by Admission Date.
These objects are coming from nHibernate and it keeps return a Not Supported exception. There is also an association between Patient and Admissions thus : Patient.Admissions but i couldn't figure out how to then add the query filters return from the function Build???Specifications.
I'd be really grateful if someone could point me in the right direction; am I up against the Linq provider implementation here in nHibernate and need to move to Criteria or is it my Linq query ?
If anyone has any links or suggestions for good books or other learning materials in this area that would also be really helpful too.

I see several potential problems:
If you're using NHibernate 2.x + Linq2NHibernate explicit joins like that are not supported; in other versions they're just considered a smell.
I dont think NHibernate supports calling parameterized constructors in select clauses
I'm very sure NHibernate does not support calling instance methods in the select lambda
I'd suggest using the lambda syntax and SelectMany to alleviate potential join issues. Points #2 & #3 can be solved by projecting into an anonymous type, calling AsEnumerable then projecting into your model type.
Overall I'd suggest restructuring your code like:
var patientSpec = patientSearch.BuildPatientSpecification();
var admissionSpec = patientSearch.BuildAdmissionSpecification();
_patientSearchResultModel = _patientRepository.Where(patientSpec)
.SelectMany(p=>p.Admissions).Where(admissionSpec)
.Select(a=> new {
PatientId = a.Patient.Id,
AdminssionId = a.Id,
a.PhaseType,
a.Patient.Last,
a.Patient.First,
a.InPatientLocation,
a.AdmissionDate,
a.DischargeDate,
a.RRI,
a.CompletionStatus,
a.FollowupStatus
}).AsEnumerable()
.Select(x=> new PatientSearchResultModel(x.PatientId, x.AdmissionId ...))
.ToList();

Divide your query into parts and check which part runs and which doesn't.
My take on this is that select new ... is not supported in Linq to nHibernate.
I would recomend using something else, because it is simply too imature and feature-less to use seriously.

As with most popular LINQ-to-Database query providers, NHibernate will try to translate the whole query into a SQL statement to run against the database. This requires that all elements of your query are possible to express in the SQL flavour you're using.
In your query, the select new statement cannot be expressed in SQL, because you're making a call to the constructor of your PatientSearchResultModel class and are making a call to a GetPhaseTypeModel method.
You should restructure your query to express what you want to execute on the SQL database, then call AsEnumerable() to force the remainder of the query to be evaluated in-memory. After that call, you can call the constructor of your class and any .NET methods, and they will be executed as native code.

This query is too complex to describe it using Linq. It would give wrong result finally (if Patient has more than one admission records, result would have duplicate entries).
I see two steps for solution:
1) At development stage, use in-memory query. So, take Patients using ToList() first (query db at this moment). Some predicates (Patient filter like MRN, First, Last) could be used at this stage.
And then do search in-memory. Not performance, but working solution. Mark it for refactor to optimize later.
2) Finally, use NHibernate IQuery (ISQLQuery) and build sql query manually to make sure it would work as expected and work fast enough on SQL Server side. This is just read-only query and do not require Nhibernate query engine (Linq to Nhibernate) at all.

SubSonic .Paged() query returns duplicate records

Using a SubSonic (2.2) SqlQuery object, I am querying a view that contains distinct rows from another table. The results of the query, however, contain multiple rows for certain rows in the view. It appears to be because of a join on a temporary table in the query generated to achieve paging. How can I avoid this duplication of rows?
Bonus points: I have to use the view because SubSonic can't do .Paged() and .Distinct() at the same time. Why not?

If I remember correctly you have to use distinct on the right position.
var query = DB.Select().From<Products>()
.Where(Products.CategoryColumn).IsEqualTo(5).Distinct();
var query = DB.Select().Distinct().From<Products>()
.Where(Products.CategoryColumn).IsEqualTo(5);
Both statements compile but the first generates invalid sql code. A good starting point for debugging SubSonic SqlQueries is to generate the output:
var sql = query.BuildSqlStatement();
Another solution could be to use Group instead of distinct so you can avoid the view in the first place.