So for various reasons we need to send a large list of Ids to a EF6 query.
queryable.Where(x => list.Contains(x.Id));
is not ideal since it will create a huge were list.
So I was thinking, would it be possible some homehow to pass a table value parameter with the ids and get a IQueryable back that I can join against?
something like (Pseudo code)
var queryable = TableValueToIQueryable<MyTableValueType>(ids);
context.Set<MyEntity>().Join(queryable, x => x.Id, x.Value, (entity, id) => entity);
Is this possible somehow?
update: I have been able to use EntityFramework.CodeFirstStoreFunctions to execute a sql function and map the data to IQueryable<MyEntity>. it uses CreateQuery and ObjectParameters, can I use table value params somehow with ObjectParamters?
update2: Set().SqlQuery(...) will work with Table value parameters, but the resulting DbSqlQuery is not Joinable in SQL with a IQueryably so the result will be two connections and the join is done in memory
var idResult = Set<IdFilter>().SqlQuery("select * from GetIdFilter(#ids)", parameter);
var companies = idResult.Join(Set<tblCompany>(), x => x.Id, y => y.CompanyID, (filter, company) => company).ToList();
update3: ExecuteStoreQuery
((IObjectContextAdapter)ctx).ObjectContext.ExecuteStoreQuery<InvoicePoolingContext.IdFilter>("select * from dbo.GetIdFilter(#ids)", parameter)
.Join(ctx.Set<tblCompany>(), x => x.Id, y => y.CompanyID, (filter, company) => company).ToList();
Gives error:
There is already an open DataReader associated with this Command which
must be closed first.
Related
I am trying to build a query using asp.net core c#
https://www.reflectionit.nl/blog/2017/paging-in-asp-net-core-mvc-and-entityframework-core
I trying to do a filtering however I need the data from another table which have my unique id
var result = _context.UserRoles.Where(y => y.RoleId.Contains(selectedRoles.Id)); // Retrieve the the userid i have from another table with the selected roleid
var query = _context.Users.Where(x => //I have already tried contains, where join );
If there is a site where i can learn this query please recommend. "Join()" does not work as I am doing paging
a least two solutions (please note that I do not check the identity classes members, so the following is the "spirit" of the solution (you miss the select clauses) ):
var result = _context.UserRoles.
Where(y => selectedRoles.Contains(y.RoleId)).
Select(y => y.User);
or
var result = _context.UserRoles.
Where(y => selectedRoles.Contains(y.RoleId)).
Select(y => y.UserId);
query = _context.Users.
Where(x => result.Contains(x.Id));
That said, assuming that there is no UserRoles table exposed in Identity (v2), you probably want:
userManager.Users.
Where(u => u.Roles.Any(r => selectecRoles.Contains(r.RoleId)));
Up to you to instanciate the userManager.
I'm trying to select objects from the database with Entity Framework into an anonymous type. When using Union and Selecting a Subcollection, I get an exception:
System.ArgumentException: The 'Distinct' operation cannot be applied to the collection ResultType of the specified argument.
My model contains several types derived from BaseType. This base type has a reference to RefType which contains a collection of ItemType. The types derived from BaseType are stored in separate tables, thus the Union.
The query looks like this:
var q1 = ctx.Set<Type1>().Select(x => new { x.Id, x.Ref.Items });
var q2 = ctx.Set<Type2>().Select(x => new { x.Id, x.Ref.Items });
q1.Union(q2).ToList();
But to reproduce the error, you can even union queries of the same type, as long as you select a collection.
I would do the select after the union, but to union Type1, Type2, etc. I must cast them to BaseType, which is not allowed in LINQ-to-SQL.
Any way to do this in the same query?
The exception emerges from Entity Framework's query generation pipeline when the ExpressionConverter tries to translate the expression q1.Union(q2) into SQL.
In a valid query you'll see that EF adds a DISTINCT clause to the SQL query. A type with collection properties (x.Ref.Items) doesn't pass as a valid argument for a Distinct operation and EF throws the exception you see.
Unfortunately, using Concat instead of Union is not a valid work-around. EF will also throw an exception:
The nested query is not supported. Operation1='UnionAll' Operation2='MultiStreamNest'
Which means that it's simply not supported to concat nested queries containing types with collection properties.
So you have to do the Union in memory:
var result = q1.AsEnumerable() // Continues the query in memory
.Union(q2).ToList();
C# doesn't have any problem with equating anonymous types containing collections: it simply considers any collection member as unequal to another collections member. This does mean that the query can produce a collection containing non-unique results (same Id, same Items) which may not be expected when relying on Union's implicit Distinct.
I am not sure why, for some reason distinct is failing, maybe because it is anonymous type, and it is still IQuerable, I would suggest firing the query something like this
var q1 = ctx.Set<Type1>().Select(x => new { x.Id, x.Ref.Items }).ToList<object>();
var q2 = ctx.Set<Type2>().Select(x => new { x.Id, x.Ref.Items }).ToList<object>();
q1.Union(q2).ToList();
Note that in this case, Distinct will check for all properties equality, meaning if 2 objects have the same id but different items, both will be there.
if you don't care about distinct values, you can also use concat
if you care about distinct and first option didn't work, you can use group by and implement your own distinct,
something like this
var q1 = ctx.Set<Type1>().Select(x => new { Id = x.Id, Items =x.Ref.Items });
var q2 = ctx.Set<Type2>().Select(x => new { Id = x.Id, Items = x.Ref.Items });
//this will group by id, and select the first object items
var qFinal = q1.concat(q2).GroupBy(e => e.id)
.select(e => new {e.key, e.First().Items})
.ToList();
maybe you don't want First(), you can use whatever you want
I'm not sure how to get the rows I need in EF. In SQL it would look something like this:
SELECT * FROM [Recipes]
JOIN [UserFavorites] ON [UserFavorites].[RecipeId] = [Recipes].[Id]
WHERE [UserFavorites].[UserId] = #UserId
I know how to get the userfavorites that match the user id like this:
db.UserFavorites.Where(x => x.UserId == userId
But then how do I get all of the recipes that match the recipeIds inside of those userfavorites?
You can either use LINQ and construct a query:
var recipes = from r in db.Recipes
join f in db.UserFavorites on r.Id equals f.RecipeId
where f.UserId = userId
select r
or you can use the lambda syntax with navigation properties, assuming you have them set up for the relationships in question
var recipes = db.Recipes.Where(r => r.UserFavorites.Any(f => f.UserId == userId));
You can, of course, construct the actual query that's described in the first section using the equivalent lambda syntax (since the query syntax is just a language feature that compiles down to the equivalent calls to the extension methods using anonymous delegates), but that tends to be a little more difficult to read.
How about:
var recipes = context.Recipes
.SelectMany(r => r.Users, (r, u) => new { Recipe = r, User = u }
.Where(o => o.User.UserId = userId)
.Select(o => o.Recipe);
This implies UserFavorites is the intersection table between Recipes and Users
Recipes >- UserFavorites -< Users
I am working on a new project and we are using Entity Framework and the dev lead would like to use lambda queries whenever possible. One thing we are having a hard time figuring out is how to select two columns specifically. Also how to select distinct. We have a table that has multiple entries for a vendor but we want to just get a list of vendors and load to a dictionary object. It fails because as written it is trying to add a key value that has already been added. Take the following query.
Dictionary<int, string> dict = new Dictionary<int, string>();
dict = GetWamVendorInfo().AsEnumerable()
.Where(x => x.vendor_name != null && x.vendor_id != null)
//.Select(x => x.vendor_id).Distinct()
.Take(2)
.ToDictionary(o => int.Parse(o.vendor_id.ToString()), o => o.vendor_name);
What I would like to do is select just vendor_id and vendor_name so we can get just the distinct records.
Any help would be greatly appreciated.
Thanks,
Rhonda
Use an anonymous type:
// earlier bit of query
.Select(x => new { VendorId = x.vendor_id, VendorName = x.vendor_name } )
.Distinct()
.ToDictionary(o => o.VendorId, o => o.VendorName);
I've removed the call to Take(2) as it wasn't clear why you'd want it - and also removed the parsing of VendorId, which I would have expected to already be an integer type.
Note that you should almost certainly remove the AsEnumerable call from your query - currently you'll be fetching all the vendors and filtering with LINQ to Objects. There's also no point creating an empty dictionary and then ignoring it entirely. I suspect your complete query should be:
var vendors = GetWamVendorInfo()
.Select(x => new { VendorId = x.vendor_id,
VendorName = x.vendor_name } )
.Distinct()
.ToDictionary(o => o.VendorId,
o => o.VendorName);
As an aside, you should ask your dev lead why he wants to use lambda expressions (presumably as opposed to query expressions) everywhere. Different situations end up with more readable code using different syntax options - it's worth being flexible on this front.
Just use an anonymous object:
var vendors = GetWamVendorInfo().AsEnumerable()
.Where(x => x.vendor_name != null && x.vendor_id != null)
.Select(new {x.vendor_id, x.vendor_name})
.Take(2)
That's it. You can now work with vendors[0].vendor_id, vendors[0].vendor_name, and so on.
I have an ASP.NET MVC application that displays data in a table format. I want to give my users the ability to search the table, so I take a text string and pass it into my service layer to construct a query using Linq to Entities.
I want to search a number of columns using the string. Some of the columns are integers (order ids), but the user doesn't care about integers and strings. They want to type '1200' and get any order with '1200' in the order number, or '1200' in the address.
The problem is that I can't find a way to construct a Linq-to-Entities query that results in SQL that looks like this:
select orderid, address from orders where orderid like '%1200%' or address like '%1200%'
Database context:
public DbSet<Person> Persons { get; set; }
public DbSet<Worker> Workers { get; set; }
public DbSet<WorkerSignin> WorkerSignins { get; set; }
The Persons and Workers tables are in a 1 to 0..1 relationship. If a worker record exists, a person record must also exist. They share the same ID. A worker record doesn't have to exist, however.
The Workers and WorkerSignins tables are related, but it's not enforced because of a client requirement. The Worker has an id-card with a barcode number on it (dwccardnum), but there may be discrepancies between cards issued and records in the DB, so I record all cards scanned in WorkerSignins, regardless of whether there is a matching record in the Workers table.
Here is the code I am working with:
allWSI = signinRepo.GetAllQ()
.Where(jj => jj.dateforsignin == date)
.Select(a => a);
if (!string.IsNullOrEmpty(search))
{
allWSI = allWSI
.Join(workerRepo.GetAllQ(), s => s.dwccardnum, w => w.dwccardnum, (s, w) => new { s, w })
.DefaultIfEmpty()
.Join(personRepo.GetAllQ(), oj => oj.w.ID, p => p.ID, (oj, p) => new { oj, p }).DefaultIfEmpty()
.DefaultIfEmpty()
.Where(jj => Convert.ToString(jj.oj.w.dwccardnum).Contains(search) ||
jj.p.firstname1.Contains(search) ||
jj.p.firstname2.Contains(search) ||
jj.p.lastname1.Contains(search) ||
jj.p.lastname2.Contains(search))
.Select(a => a.oj.s);
}
The GetAllQ() methods return an IQueryable() object.
The problem is on this line:
.Where(jj => Convert.ToString(jj.oj.w.dwccardnum).Contains(search) ||
I get this error:
LINQ to Entities does not recognize the method 'System.String ToString(Int32)' method, and this method cannot be translated into a store expression."
If I take out the convert, and try this:
.Where(jj => jj.oj.w.dwccardnum.Contains(search) ||
I get this error:
'int' does not contain a definition for 'Contains' and the best extension method overload 'System.Linq.ParallelEnumerable.Contains(System.Linq.ParallelQuery, TSource)' has some invalid arguments
So the question is...
How do I construct a Where clause to generate a like '%string%' and execute it against a integer column using Linq to Entities? (e.g. without using LINQ to SQL)
One option is to replace ...
jj => Convert.ToString(jj.oj.w.dwccardnum).Contains(search)
... by:
jj => SqlFunctions.StringConvert((decimal)jj.oj.w.dwccardnum).Contains(search)
SqlFunctions is a static class in namespace System.Data.Objects.SqlClient and I believe it only works with SQL Server. The weird cast to decimal is necessary because StringConvert doesn't have an overload for an int and without the cast the compiler complains that it cannot select the right overload unambiguously. (It has one for decimal? and one for double?.) But I just tested that the code above works indeed (with SQL Server and assuming dwccardnum is an int).
Try this
if (!string.IsNullOrEmpty(search))
{
int cardnum;
bool searchIsInt = int.TryParse(search, out cardnum);
allWSI = allWSI
.Join(workerRepo.GetAllQ(), s => s.dwccardnum, w => w.dwccardnum, (s, w) => new { s, w })
.DefaultIfEmpty()
.Join(personRepo.GetAllQ(), oj => oj.w.ID, p => p.ID, (oj, p) => new { oj, p }).DefaultIfEmpty()
.DefaultIfEmpty()
.Where(jj => (searchIsInt ? jj.oj.w.dwccardnum == cardnum : true) ||
jj.p.firstname1.Contains(search) ||
jj.p.firstname2.Contains(search) ||
jj.p.lastname1.Contains(search) ||
jj.p.lastname2.Contains(search))
.Select(a => a.oj.s);
}
Basically, you're first checking to see if the search is an int and then use it in your linq if it is.