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Using lambdas LINQ query in C#

I am still in the midst of converting our web app from vb to C# and this complex query, that I just finished converting and have tested and it works properly, needs refactoring.
This section could probably perform a little better if lambdas were used (I've read in numerous places that lambda expressions perform faster)
foreach (var datapersymbol in (from symId in symblist
select (
from q in ctx.HistoricalPriceData.Where(q => q.SymbolId == symId)
join x in ctx.Symbols on q.SymbolId equals x.SymbolId
orderby q.Date descending
select new {q.Date, q.LastPrice, x.Symbol1})).ToList())
As you can see I've added lambdas where I thought appropriate but Im certain they can be in other parts of this expressions as well. I'm still getting up to speed in C# so Im not an expert here.

Assuming you have a navigation property on HistoricalPriceData to Symbols called "Symbol":
foreach(var datapersymbol in ctx
.HistoricalPriceData
.Where(h=>symblist.Contains(h.SymbolId))
.OrderByDescending(h=>h.Date)
.Select(h=>new {h.Date,h.LastPrice,h.Symbol.Symbol1}))
As Rahul pointed out, there is no performance difference between lamda/method syntax and query syntax, however, this will perform slightly better because it drops the .ToList(), which will allow the loop to begin processing as soon as it gets the first record from the database rather than waiting for the entire result (and it doesn't need to create a List). I've also simplified it somewhat by using .Contains instead of a subquery as well, and switched to using navigation properties rather than a explicit join which makes it easier to read/more maintainable.

For the clarity of the code I will rather refactor it like below;
var datapersymbols = from symId in symblist
select (
from q in ctx.HistoricalPriceData.Where(q => q.SymbolId == symId)
join x in ctx.Symbols on q.SymbolId equals x.SymbolId
orderby q.Date descending
select new {q.Date, q.LastPrice, x.Symbol1});
foreach (var datapersymbol in datapersymbols)
{
}
As far as I can see, in this case, there is not much that you can gain from the C# side. You have to check the query plan for the SQL query and then add necessary indexes. The SymbolId field should be an indexed field.

Full Text Search with LINQ, decrease results with each keyword

I followed the directions in this SO question to create a linq function to do a full text search on a food database i have. there are over 7000 records in this DB and with each keyword i add the results get larger as opposed to smaller.
here is the meat of my function:
SELECT *
FROM USDA_Foods AS FT_TBL
INNER JOIN FREETEXTTABLE(USDA_Foods,
Shrt_Desc,
#searchWord) AS KEY_TBL
ON FT_TBL.foodId = KEY_TBL.[KEY]
How would i decrease the results with each new keyword by altering the code above?
Thanks

You get more results because it works looking for any of the words in the searched column, and not that contains all of the words, as you expect. You can't use AND or anything in FREETEXTTABLE, so you have to use something like CONTAINSTABLE, which allows you to use AND between the provided words.
CONTAINSTABLE (Transact-SQL)
Look at the example "I. Using CONTAINS with a logical operator (AND)" here:
CONTAINS (Transact-SQL)
The syntax is valid also for CONTAINSTABLE.
SELECT *
FROM USDA_Foods AS FT_TBL
INNER JOIN CONTAINSTABLE(USDA_Foods,
Shrt_Desc,
#searchWord) AS KEY_TBL
ON FT_TBL.foodId = KEY_TBL.[KEY]
Your #searchWord should look like
'here AND there AND everywhere'
to look for text that contains here, there and everywhere.

Concatenate INNER JOINS for each search word.
SELECT *
FROM USDA_Foods AS FT_TBL
INNER JOIN FREETEXTTABLE(USDA_Foods,
Shrt_Desc,
#searchWord1) AS KEY_TBL1
ON FT_TBL.foodId = KEY_TBL1.[KEY]
INNER JOIN FREETEXTTABLE(USDA_Foods,
Shrt_Desc,
#searchWord2) AS KEY_TBL2
ON FT_TBL.foodId = KEY_TBL2.[KEY]

Sort Linq list with one column

I guess it should be really simple, but i cannot find how to do it.
I have a linq query, that selects one column, of type int, and i need it sorted.
var values = (from p in context.Products
where p.LockedSince == null
select Convert.ToInt32(p.SearchColumn3)).Distinct();
values = values.OrderBy(x => x);
SearchColumn3 is op type string, but i only contains integers. So i thought, converting to Int32 and ordering would definitely give me a nice 1,2,3 sorted list of values. But instead, the list stays ordered like it were strings.
199 20 201
Update:
I've done some tests with C# code and LinqPad.
LinqPad generates the following SQL:
SELECT [t2].[value]
FROM (
SELECT DISTINCT [t1].[value]
FROM (
SELECT CONVERT(Int,[t0].[SearchColumn3]) AS [value], [t0].[LockedSince], [t0].[SearchColumn3]
FROM [Product] AS [t0]
) AS [t1]
WHERE ([t1].[LockedSince] IS NULL)
) AS [t2]
ORDER BY [t2].[value]
And my SQL profiler says that my C# code generates this piece of SQL:
SELECT DISTINCT a.[SearchColumn3] AS COL1
FROM [Product] a
WHERE a.[LockedSince] IS NULL
ORDER BY a.[SearchColumn3]
So it look like C# Linq code just omits the Convert.ToInt32.
Can anyone say something useful about this?

[Disclaimer - I work at Telerik]
You can solve this problem with Telerik OpenAccess ORM too. Here is what i would suggest in this case.
var values = (from p in context.Products
where p.LockedSince == null
orderby "cast({0} as integer)".SQL<int>(p.SearchColumn3)
select "cast({0} as integer)".SQL<int>(p.SearchColumn3)).ToList().Distinct();
OpenAccess provides the SQL extension method, which gives you the ability to add some specific sql code to the generated sql statement.
We have started working on improving this behavior.
Thank you for pointing this out.
Regards
Ralph

Same answer as one my other questions, it turns out that the Linq provider i'm using, the one that comes with Telerik OpenAccess ORM does things different than the standard Linq to SQL provider! See the SQL i've posted in my opening post! I totally wasn't expecting something like this, but i seem that the Telerik OpenAccess thing still needs a lot of improvement. So be careful before you start using it. It looks nice, but it has some serious shortcomings.

I can't replicate this problem. But just make sure you're enumerating the collection when you inspect it. How are you checking the result?
values = values.OrderBy(x => x);
foreach (var v in values)
{
Console.WriteLine(v.ToString());
}
Remember, this won't change the order of the records in the database or anywhere else - only the order that you can retrieve them from the values enumeration.

Because your values variable is a result of a Linq expression, so that it doest not really have values until you calling a method such as ToList, ToArray, etc.
Get back to your example, the variable x in OrderBy method, will be treated as p.SearchColumn3 and therefore, it's a string.
To avoid that, you need to let p.SearchColumn3 become integer before OrderBy method.
You should add a let statement in to your code as below:
var values = (from p in context.Products
where p.LockedSince == null
let val = Convert.ToInt32(p.SearchColumn3)
select val).Distinct();
values = values.OrderBy(x => x);
In addition, you can combine order by statement with the first, it will be fine.

Joins and subqueries in LINQ

I am trying to do a join with a sub query and can't seem to get it. Here is what is looks like working in sql. How do I get to to work in linq?
SELECT po.*, p.PermissionID
FROM PermissibleObjects po
INNER JOIN PermissibleObjects_Permissions po_p ON (po.PermissibleObjectID = po_p.PermissibleObjectID)
INNER JOIN Permissions p ON (po_p.PermissionID = p.PermissionID)
LEFT OUTER JOIN
(
SELECT u_po.PermissionID, u_po.PermissibleObjectID
FROM Users_PermissibleObjects u_po
WHERE u_po.UserID = '2F160457-7355-4B59-861F-9871A45FD166'
) used ON (p.PermissionID = used.PermissionID AND po.PermissibleObjectID = used.PermissibleObjectID)
WHERE used.PermissionID is null

Without seeing your database and data model, it's pretty impossible to offer any real help. But, probably the best way to go is:
download linqpad - http://www.linqpad.net/
create a connection to your database
start with the innermost piece - the subquery with the "where" clause
get each small query working, then join them up. Linqpad will show you the generated SQL, as well as the results, so build your small queries up until they are right
So, basically, split your problem up into smaller pieces. Linqpad is fantastic as it lets you test these things out, and check your results as you go
hope this helps, good luck
Toby

The LINQ translation for your query is suprisingly simple:
from pop in PermissibleObjectPermissions
where !pop.UserPermissibleObjects.Any (
upo => upo.UserID == new Guid ("2F160457-7355-4B59-861F-9871A45FD166"))
select new { pop.PermissibleObject, pop.PermissionID }
In words: "From all object permissions, retrieve those with at least one user-permission whose UserID is 2F160457-7355-4B59-861F-9871A45FD16".
You'll notice that this query uses association properties for navigating relationships - this avoids the need for "joining" and simplfies the query. As a result, the LINQ query is much closer to its description in English than the original SQL query.
The trick, when writing LINQ queries, is to get out of the habit of "transliterating" SQL into LINQ.

LINQ: Help with linq query and contains for an IEnumerable<string>?

Can anyone help?
I have a linq query which is embedded inside a extension method, it was working as v.RentalStatus was a String. I am now using a Group on my original query (the query is quite complex so i won't put it here).
The importante thing is that v.RentalStatus = IEnumerable hence it can contain things like
A (meaning active)
R (meaning rented)
U (unavailable)
etc - many more
I create a list of what i would like to get back and store this in statusStringList, so for example lets say the list contains A and R
This is my code from before when the v.RentalStatus was just a string, can anyone tell me how i can modify this to work.
var statusStringList = rentalStatus.ToList().ConvertAll<string>(st => st.GetStringValue());
return from v in qry
where statusStringList.Contains(v.RentalStatus)
select v;
If it helps this is part of my query which returns the RentalStatus - its part of a group query but the RentalStatus is not in the group by
RentalStatus= g1.Select( j => j.IdRentalStatus).Distinct(),
g1 is my group by, so if you imagine there are 10 "A", 5 "U" .. then it would return an ienumerable of A and U ... as i am using Distinct. Not 10 As and 5 Us
I hope i have explained it well, please tell me if i haven't
I would appreciate any help from anyone ..
thanks
EDIT
This is my extension signature but not that it matters.
public static IQueryable<Rentals> WithStatus(this IQueryable<Rentals> qry, IList<Contants.Statuses> rentalStatus)
{
EDIT
As mentioned previously when v.RentalStatus was a string it was working but now its IEnumerable - hence a collection.. and it errors with this
Argument '1': cannot convert from 'System.Collections.Generic.IEnumerable<string>' to 'string'

If RentalStatus has changed from a string to a IEnumerable<string> then your comparing 2 list... I think this should work:
return from v in qry
where v.RentalStatus.Any(status => statusStringList.Contains(status))
select v;
This should give you any rentals that have a status that is in the list you are providing
Edit:
Yeah I would spend some time learn lambda expressions. Seems like they are being used more and more and with good reason. Here are a few links for tutorials:
An Extensive Examination of LINQ: Lambda Expressions and Anonymous Types
.NET Lambda Expressions – Resources
"WHERE" RentalStatus = Containing any
of itself - arrgghh -
Is that true? I thought the list of rentalStatuses is a parameter in your method. I was thinking your query basically would allow me to get all the rentals that have a status that matches any of the list that I specified. One list lives on your Rental object and the other is the one I pass in...
As to why the order in mine worked. I have some questions:
Are you using this to query a database? Are you able to look at the tsql it generates?
If so, I would look at the tsql and see what the difference is. I would have to check myself. I got lucky I guess.

You could try something like this:
where statusStringList.Any(x => v.RentalStatus.Contains(x))

I am not sure but I think that for a Contains to work in Linq to SQL it must be an array of strings (or ints or ...) and not any IEnumerable. I would thus try:
var statusStringArray = rentalStatus.ToList().ConvertAll<string>(st => st.GetStringValue()).ToArray();
return from v in qry
where statusStringArray.Contains(v.RentalStatus)
select v;
There might be other issues though, I did not look that much.

Try this:
return from v in qry
where rentalStatus.Any( r => r.IdRentalStatus == v.RentalStatus)
select v;