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.
Related
We are using EFCore.SqlServer.HierarchyId to represent a hierarchy in our data.
My goal is to return the descendants of an object with a particular path of indeterminate length, e.g. given a tree with the hierarchy one->two->three->four, the path one/two/three would return four
Knowing the length of the path, I can make a query like this:
var collections = await context.Collections.Where(c => c.CollectionHierarchyid.IsDescendantOf(
context.Collections.FirstOrDefault(c1 => c1.FriendlyId == "three" &&
context.Collections.Any(c2 => c2.CollectionHierarchyid == c1.CollectionHierarchyid.GetAncestor(1) && c2.FriendlyId == "two" &&
context.Collections.Any(c3 => c3.CollectionHierarchyid == c2.CollectionHierarchyid.GetAncestor(1) && c3.FriendlyId == "one")
)
).CollectionHierarchyid
)).ToListAsync();
But how would you go about this if the length of the path is unknown? I can't call a recursive function from the expression because it won't compile from Linq to Entity Sql.
I know the answer lies somewhere in using System.Linq.Expressions to build the expression, but I am not sure where to start.
The problem can be solved without dynamic expression tree generation, at least not directly, but using standard LINQ query operators.
Let say you have a hierarchical entity like this
public class Entity
{
public HierarchyId Id { get; set; }
// other properties...
}
Given a subquery returning the full set
IQueryable<Entity> fullSet = context.Set<Entity>();
and subquery defining some filtered subset containing the desired ancestors
IQueryable<Entity> ancestors = ...;
Now getting all direct and indirect descendants can easily be achieved with
IQueryable<Entity> descendants = fullSet
.Where(d => ancestors.Any(a => d.Id.IsDescendantOf(a.Id));
So the question is how to build ancestors subquery dynamically.
Applying some filter to the full set and retrieving the direct ancestors filtered by another criteria can be done by using simple join operator
from p in fullSet.Where(condition1)
join c in fullSet.Where(condition2)
on p.Id equals c.Id.GetAncestor(1)
select c
Hence all you need is to apply that recursively, e.g. having
IEnumerable<TArg> args = ...;
representing the filtering criteria arguments ordered by level, then the query can be built as follows
var ancestors = args
.Select(arg => fullSet.Where(e => Predicate(e, arg)))
.Aggregate((prevSet, nextSet) =>
from p in prevSet join c in nextSet on p.Id equals c.Id.GetAncestor(1) select c);
With that being said, applying it to your example:
IEnumerable<string> friendlyIds = new [] { "one", "two", "three" };
var fullSet = context.Collections.AsQueryable();
var ancestors = friendlyIds
.Select(friendlyId => fullSet.Where(e => e.FriendlyId == friendlyId))
.Aggregate((prevSet, nextSet) =>
from p in prevSet join c in nextSet on p.CollectionHierarchyid equals c.CollectionHierarchyid.GetAncestor(1) select c);
var descendants = fullSet
.Where(d => ancestors.Any(a => d.CollectionHierarchyid.IsDescendantOf(a.CollectionHierarchyid));
I updated my .net core 2.2 to 5
I have a error about ef that
System.InvalidOperationException: 'The LINQ expression 'x' could not
be translated. Either rewrite the query in a form that can be
translated, or switch to client evaluation explicitly by inserting a
call to 'AsEnumerable', 'AsAsyncEnumerable', 'ToList', or
'ToListAsync'. See https://go.microsoft.com/fwlink/?linkid=2101038 for
more information.'
public List<CustomerPageModel> GetCustomers(int AccountID)
{
return (from p in context.Customers
join f in context.Patients on p.ID equals f.CustomerID into ps
from t in ps.DefaultIfEmpty()
where p.AccountID == AccountID
select new CustomerPageModel
{
ID = p.ID,
Name = p.Name,
IsActive = p.IsActive,
TC = p.TC,
Surname = p.Surname,
Email = p.Email,
Address = p.Address,
Phone = p.Phone,
Note = p.Note,
AccountID = p.AccountID,
Pats = string.Join(",", ps.Select(x => x.Name)),
PatCount = ps.Count()
})
.GroupBy(p => p.ID)
.Select(g => g.First())
.ToList();
}
How can I convert that code?
Your problem line is:
Pats = string.Join(",", ps.Select(x => x.Name)),
Specifically, the string.Join method doesn't translate to SQL, so in previous versions of EF, it had to retrieve the data from the database then in-memory preform the string.Join function. Now EF explicitly tells you it can't run that on the database server - this is a breaking change but a design decision that tells you (the developer) that it may not have been running as efficiently as you thought it was...
To "fix" this, and based on your particular code example I'd recommend the following:
Add a pet names array property to your CustomerPageModel:
public string[] PetNames {get;set;}
And turn the Pets property into a readonly calculated string:
public string Pets { get => string.Join(",", PetNames); }
And change the problem line in your LINQ expression to:
PetNames = ps.Select(x => x.Name).ToArray()
I changed (lamb to subquery)
string.Join(",", ps.Select(x => x.Name))
to
string.Join(",", (from y in PatientList where y.CustomerID == p.ID select y.Name).ToArray()),
I made the group later (after tolist)
var test = mylist.GroupBy(p => p.ID)
.Select(g => g.First())
.ToList();
problem solved
I'm using entity framework to connect to database from my application. I have table in SQL, named Orders. It contains such fields as: TransactionId, ParticipantId and is linked to Transactions table which has one to many connection to Participants table. I need to get data from it using List of classes with such properties: TransactionId, ParticipantId, OrganizationId. Linq must meet such conditions: (orders.TransactionId == TransactionId && orders.ParticipantId == ParticipantId && orders.Transaction.Participants.Any(x=> x.Id == OrganizationId)). This should be done by one query, not by multiple, so, please don't recommend foreach or smth like that.
Like #NetMage said, generally we need examples. Assuming that you've got a dbcontext set up, the ask is pretty simple:
public static void GetData(int transactionId, int participantId, int organizationId)
{
using (var db = new MyDbContext())
{
var query =
(
from t in db.Transactions
from o in db.Orders
.Where(w => w.TransactionId == t.TransactionId)
from p in db.Participants
.Where(w => w.TransactionId == t.TransactionId)
where t.TransactionId = transactionId &&
o.ParticipantId = participantId
select new { Order = o, Transaction = t, Participant = p}
);
}
}
Again since we don't have a lot of information here it's hard to do more. You should be able to take it from there. I know I didn't use the organizationId filter, but since I don't know the target shape of the data I'm not sure what the best path would be
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.
Currently, to do a search using EF CodeFirst and a repository pattern, based on user input to multiple text boxes on an mvc search view/page, I do something like the following:
public PagedList<Entity1> PlayerUserSearch(Entity1SearchParameters searchParameters, int? pageSize, int? startEntity, Func<Entity1, object> sortOrder, bool sortDesc)
{
IQueryable<Entity1> query = from entities in this.DataContext.Entity1s.Include("Entity2List")
where entities.Entity2List.Any()
select entities;
if (searchParameters.Entity2PrimaryKeyId.HasValue)
query = query.Where(e => e.Id == searchParameters.Entity2PrimaryKeyId.Value);
if (searchParameters.HasStats.HasValue)
{
if (searchParameters.HasStats.Value)
query = query.Where(u => u.Entity2List.Any(e => e.Stat != null));
else
query = query.Where(u => u.Entity2List.Any(e => e.Stat == null));
}
if (searchParameters.Entity2OtherField.HasValue)
query = query.Where(u => u.Entity2List.Any(e => e.Event.Entity2OtherField == searchParameters.Entity2OtherField));
if (searchParameters.Entity2OtherField2.HasValue)
query = query.Where(u => u.Entity2List.Any(e => e.Event.Entity2OtherField2 == searchParameters.Entity2OtherField2));
if (searchParameters.Active.HasValue)
query = query.Where(e => e.Active == searchParameters.Active.Value);
return this.GetPageByStartEntity(pageSize.Value, startEntity.Value, query, sortOrder, sortDesc);
}
The problem with this is that for every time I add on another where that checks the child of Entity1 (Entity2) for a certain field, it takes on a new " AND EXISTS" clause to the sql statement generated, so that it is doing an exists and checking table Entity2 all over again for every different field checked, rather than doing a single EXISTS on Entity in the query, and checking all fields I tacked on to the query (i.e. EntityOtherField1 and EntityOtherField2). I haven't been able to find a better way to do a search based on user inputs than constantly checking for the input being there (add to the search parameters)) and then tacking on a new where to the current query. Can anyone tell me if there is a better way to do this? Thanks!
I think what you're looking for is using Specification Pattern.
var spec = new specification<Entity2>(s => true);
if (searchParameters.HasStats.Value)
{
spec = spec.And(e => e.Stat != null);
}
if (searchParameters.Entity2OtherField2.HasValue)
{
spec = spec.And(e => e.Event.Entity2OtherField2 == searchParameters.Entity2OtherField2);
}
query = query.Where(u => u.Entity2List.Any(spec));
Or I believe you can make it more standard by separating the filter logic and using spec.IsStatisfiedBy method.
A good framework for repository/specification implemetation on Entity Framework can be found here.