All Questions
Tagged with iqueryable ienumerable
115 questions
2
votes
2
answers
156
views
Is it bad to call First() multiple times on an IEnumerable<T> that is actually a List<T>?
I found this method:
public async Task SomeMethod(IEnumerable<Member> members)
{
await DoSomething(members.First());
await DoSomethingElse(members.First());
}
It's being called like ...
0
votes
1
answer
352
views
IQueryCollection.ToList() combines values unwantedly
My project uses two libraries:
Swashbuckle.ASPNetCore
FluentValidation
Im writing a validator interceptor to do some additional checks that are needed seperately from the validator: MyModelValidator ...
-1
votes
1
answer
1k
views
C# List.AsQueryable() returns System.Collections.Generic.List instead of IQueryable
I have a list of objects List<Student> that I want return as an IQueryable<Student>.
When I try to use .AsQueryable() on the list to convert it to IQueryable<Student> I got a System....
1
vote
1
answer
156
views
Effects of IEnumerable and IQueryable on Relational Database and Non-Relational Database
I have started to learn Linq recently, So I came across IQueryable and IEnumerable. I have understood the difference and where to use what. But I have a small doubt will IEnumerable and IQueryable ...
0
votes
1
answer
108
views
LastOrDefault() not supported on IQueryable {document}{}.LastOrDefault()is not supported
IQueryable<Patients> patients = db.Patients;
patients = patients.Where(x => x.Status.LastOrDefault().Status != Status.Imported);
On the 1st line I have a IQueryable data. (1,000+ data)...
4
votes
0
answers
1k
views
EF Core difference between AsEnumerable and AsAsyncEnumerable [closed]
Are there any differences in behavior or performance between AsEnumerable, AsAsyncEnumerable and simple iteration over IQueryable in EF Core?
// Using .AsEnumerable();
var blogs = context.Posts.Where(...
0
votes
2
answers
120
views
How does the behavior of .Take() changes based on the interface reference I'm using on left. IQueryable vs IEnumerable
Assume I've these sample codes
IQueryable<Employee> data = context.Employees.Where(x => x.FullName != "Shekar Reddy");
var topEmp = data.Take(1);
...
0
votes
1
answer
116
views
C# Make one expression tree into two (or two new expression trees with divided logic)
This question was already answer in the opposite way here, but reverting the logic is easier said than done.
So let me give you a very concrete example:
I have this :
e => e.Description == "...
-1
votes
1
answer
190
views
Iterate through Linq fluent API methods (C#) [closed]
I am looking for a way to iterate through a collection of Linq methods, previously built, and then manipulate them, like change the expression tree.
Here is an example:
what i simply want to do is a ...
0
votes
0
answers
126
views
IQueryable (PLINQ) peek and group Linq methods to run in different tasks
I want to divide a IQueryable into several ones, like the image below, extracted from the explanation of the .AsParallel(). But instead of running all in parallel, I want to run some of them together, ...
1
vote
1
answer
171
views
IEnumerable and IQueryable - the best of both worlds
For performance reasons many of my services are returning IQueryables right now, so the caller can decide what elements to filter before they get materialized. For design reasons (interfaces etc.) I'd ...
0
votes
0
answers
212
views
EntityFramework - Querying data with IQueryable/IEnumerable - "An operation is already in progress" error happens only with Npgsql.EF5
“An operation is already in progress”: Issue with data access with EntityFramework5.Npgsql for EF 5.
Although same code for data access works perfectly for oracle.
Why is this error received on ...
1
vote
0
answers
174
views
Unit/Integration tests with inmemory database don't work with IQueryables
I'm trying to run some unit tests with inmemory database. I'm creating a new entity and then I'm checking if it exists or not. If I query as an Task<IEnumerable<Entity>> or a Task<...
0
votes
2
answers
785
views
Building a multiple/single condition search function in NET.Core (IQueryable or IEnumerable)
I am a beginner in coding in C# (and coding in general, really) and I am trying to create a website to search a SQL Server database for multiple and/or single conditions simultaneously. So far it ...
0
votes
0
answers
65
views
Should the synchronous operation that build the query to DB be wrapped into Task.FromResult()
I have a code and I'm feeling (but not quite sure) there is a code smell in it:
This method calls repository method GetAllByOrderIdAsync:
List<IncomingBatch> incomingBatches =
(...
1
vote
4
answers
2k
views
When should I use IEnumerable and when IQueryable?
I have tried to look for a difference quite a few times and there are multiple answers.
One of the common known difference is that IEnumerable filters data from within memory while IQueryable does it ...
0
votes
3
answers
5k
views
Use WhereIf for multiple condition in c#
Hi can someone help me how best we can use whereif in LINQ, here I have a code which works fine, but I want to convert this query with WhereIf.
public async Task LoadQuery(IEnumerable<string&...
0
votes
1
answer
190
views
IQueryable vs IEnumerable and polymorphism where an object knows which subclass it is
When explicitly declaring the type of a query with IEnumerable such as
IEnumerable<string> q =
from c in db.Customers
select c.ContactName;
var q2 = q.Where(s => s....
4
votes
3
answers
233
views
C# extension methods types
In C#, There are two sets of extension methods (such as Where) which works on top of IEnumerable and IQueryable. which of them used for manipulate in-memory objects and which is used for working with ...
1
vote
2
answers
254
views
How do you know if a collection will act as IEnumerable or IQueryable?
I have this line of code:
var attachments = EntityRepository<Attachment>().Entities
.Where(at => at.EntityType == EntityType.EmailTemplate)
.ToDictionary(at => at.Extension, at => at);
...
0
votes
2
answers
110
views
Trouble with LINQ Returning Results Set from Object[] Array Within Object
Consider the following code:
var articlesDisplay = from product in db.ProductSearchData
select product.articles;
articlesDisplay = articlesDisplay.Where(a => a[].body....
0
votes
0
answers
200
views
IQueryable.Concat, IEnumerable.Concat, Linq GroupBy then OrderBy within each group
What I'm doing so far is this:
Entities:
public class BaseEntity
{
public int Id { get; set; }
public DateTime CreateOn { get; set; }
}
public class Request : BaseEntity, IAggregateRoot
{
...
0
votes
2
answers
454
views
Why Dbset implement IEnumerable when it already implements IQueryable?
Dbset seems to implement IEnumerable when it already has IQueryable, doesn't this makes the implementation of IEnum redundant as IQueryable already implements IEnum.
0
votes
1
answer
47
views
I try to return a List type from AccessLayer to a datagrid on Windows form but get ArgumentNullException
I am trying to keep developing my program in order to improve my knowledge on C#
But I am stuck again.
Problem is
I am trying to call a method inside Business layer in order to fill my product ...
0
votes
1
answer
370
views
What will trigger an Entity Framework IQueryable query, in a helper class that inherits List<T>?
I took this from Nerd Dinner and elsewhere,
public class PaginatedList<T> : List<T> {
public int PageIndex { get; private set; }
public int PageSize { get; private set; }
...
1
vote
0
answers
247
views
Materialize partial set of results with EF Core 2.1
Let's say I have a large collection of tasks stored in DB and I want to retrieve the latest one according to requesting user's permissions. The permissions checking logic is complex and not related to ...
0
votes
0
answers
36
views
IEnumerable from LINQToSQL, where data is stored before/ and during iteration / .NET
I have read a lot of questions/answers here , but I don´t get it.
In case you are using LINQtoSQL
IEnumerable<Car> CarsInSale= context.Cars.Where(x=> x.Model=="Ferrari");
foreach(Car car ...
0
votes
2
answers
297
views
How to convent viewmodel to Expression<Func<T,bool>>?
Piggybacking off of a very similar question...
I need to generate an Expression from a ViewModel to pass as a search predicate for IQueryable.Where. I need to be able to include/exclude query ...
1
vote
1
answer
685
views
Execute a textual SQL query on an IQueryable
I am trying to convert IQueryable to IEnumerable using SQL query. I am not sure if it's possible.
var id = "123";
string queryString = "SELECT * FROM c WHERE c.ID = " + id;
...
0
votes
1
answer
492
views
MVC Core IEnumerable Advantages over IQueryable [closed]
If IQueryable has all the functions of IEnumerable, but allows additional functionalities, why even use IEnumerable?
What are the benefits of IEnumerable over IQueryable?
Reading everything here, ...
5
votes
1
answer
2k
views
IEnumerable vs IQueryable in OData and Repository Pattern
I watched this video and read this blog post. There is something in this post confused me; The last part of the post. In the last part Mosh emphasized, Repository should never return IQueryable, ...
4
votes
3
answers
12k
views
IEnumerable and Lazy loading
I have below model -
public class Student
{
public int StudentID { get; set; }
public string StudentName { get; set; }
public Nullable<int> StandardId { get; set; }
public ...
2
votes
1
answer
3k
views
How do I use Paging on a List<T>
I have the following and wish to implement paging but I get an error when doing so. I do not receive this error when I perform the paging directly on a query result that returns from LINQ as ...
2
votes
0
answers
223
views
Linq to Sql - returning IEnumerable without using Lists [duplicate]
I'm wanting to write a function using Linq to Sql that will return an IEnumerable<TEntity>, in such a way that the results are truly enumerated from the database as they are consumed.
The wrong ...
-1
votes
1
answer
2k
views
IEnumerable can't convert to IQueryable
Until now, I have a .net 4.7 library in which I use IQuery in this mode:
IQueryable<MyType> myIQueryable = mySource;
if(paramIsNew != null)
{
myIQueryable = myIQueryable.where(x => x....
0
votes
0
answers
153
views
IQueryable vs IEnumerable - why the former doesn't support closure?
This code:
var query = from category in db.GlobalCategories // <- IQueryable DB call.
let button = new XElement("Button").Attr("Name", category.Name)
select button;
query....
1
vote
3
answers
6k
views
Real example of the differences between IQueryable and IEnumerable? [duplicate]
I know that IQueryable has the advantage of running filters on server rather loading all records in memory like IEnumerable, but how does exactly this look like in code, for example, if I have this ...
0
votes
1
answer
616
views
How to create the IQueryable version of IEnumerable extension method?
Lately, I became more interested in the differences between IEnumerable and IQueryable interfaces, hence, I found that IQueryable could be very efficient in many cases over IEnumerable, though I'm ...
5
votes
1
answer
10k
views
IQueryable vs IEnumerable: is IQueryable always better and faster?
If the IQueryable interface performs the query expression in the server rather than fetching all records like IEnumerable, why is IQueryable not replaced by IEnumerable where it can be faster and more ...
4
votes
2
answers
920
views
If IQueryable<T> inherits IEnumerable<T> , how come IQueryable<T> is LINQ to SQL?
IEnumerable<T> case is LINQ-to-object and IQueryable<T> is the interface that allows LINQ-to-SQL , however IQueryable<T> inherits IEnumerable<T> , so how is it possible to ...
0
votes
1
answer
735
views
Projecting to domain class with constructor with EF with AsEnumerable
TL;DR
Is AsEnumerable() on an IQueryable() safer to use (as in, does it already execute as ToList()) to have a workaround (see below) for the error automapper Only parameterless constructors and ...
0
votes
1
answer
408
views
Method not found on release build
Lately, I encountered a slowdown in my website and already found the cause. The reason behind is because the methods in my DA layer has IEnumerable parameters instead of IQueryable. I already ...
0
votes
1
answer
88
views
Why does C# compiler allow use of a dynamic operation in expression tree if ToList or ToArray is called
Please note: I am aware that there are many related to the main error message discussed here but I could not find any post that discusses my question.
Therefore, please be kind to read to the end ...
1
vote
0
answers
217
views
order by descending bug LINQ
This is mostly a curiosity rather than a real problem as I've already fixed that bug. I would be glad to have a deep answer that explain the LINQ mechanics behind this wizardry. So I have this query:
...
0
votes
0
answers
80
views
IQueryable returning nulls, IEnumerable does not
I have an extension method that needs to return some DTOs based on an IQueryable it receives. Tinkering with the code today (I added a new int property) I realized the method was not working properly ...
2
votes
1
answer
907
views
Why do Queryable.SelectMany(...) overloads accept Func<S, IEnumerable<R>> instead of Func<S, IQueryable<R>>?
Consider the following function:
IQueryable<Bar> foo(IEnumerable<IQueryable<Bar>> sources)
{
return
from source in sources.AsQueryable()
from bar in source
...
-1
votes
1
answer
1k
views
Why do we need to avoid using IQueryable directly in an ASP.NET MVC view?
I'm being told that putting a direct reference to IQueryable from an ASP.NET MVC view is a bad practice but I have not found any clear explanation for that. Some might have experienced a "disposed ...
4
votes
2
answers
2k
views
IEnumerable works but Type or namespace IQueryable could not be found - MVC 5
I'm using MVC5 and trying to make a simple list. I used the scaffolding, which creates the model as IQueryable in the Controller, and IEnumerable in the View. I'm trying to change the view to also ...
0
votes
2
answers
128
views
When is IEnumerable preferred over IQueryable in Entity Framework?
I understand how IEnumerable and IQueryable works. I just cannot imagine a situation where IEnumerable would be needed in entity framework when working with SQL database. I wonder if I can just ...
0
votes
2
answers
638
views
Would using an extension method to query an IEnumerable be equivalent to using IQueryable?
I understand the main difference between IQueryable and IEnumerable. IQueryable executes the query in the database and returns the filtered results while IEnumerable brings the full result set into ...