Questions tagged [entity-framework]
For questions about Entity Framework for .net framework, max. version 6.4, December 2019. Use [entity-framework-core] for current .net (core) versions. Then also please add a version-specific [ef-core-xx] tag.
91,919
questions
878
votes
29
answers
939k
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Validation failed for one or more entities. See 'EntityValidationErrors' property for more details [duplicate]
I am having this error when seeding my database with code first approach.
Validation failed for one or more entities. See 'EntityValidationErrors' property for more details.
To be honest I don't ...
- 33.3k
868
votes
17
answers
293k
views
Entity Framework vs LINQ to SQL [closed]
Now that .NET v3.5 SP1 has been released (along with VS2008 SP1), we now have access to the .NET entity framework.
My question is this. When trying to decide between using the Entity Framework and ...
- 18.7k
821
votes
12
answers
674k
views
How can I retrieve Id of inserted entity using Entity framework?
I have a problem with Entity Framework in ASP.NET. I want to get the Id value whenever I add an object to database. How can I do this?
According to Entity Framework the solution is:
using (var context ...
- 8,243
810
votes
26
answers
542k
views
How do I view the SQL generated by the Entity Framework?
How do I view the SQL generated by entity framework ?
(In my particular case I'm using the mysql provider - if it matters)
- 227k
808
votes
32
answers
580k
views
Fastest Way of Inserting in Entity Framework
I'm looking for the fastest way of inserting in Entity Framework.
I'm asking this because of the scenario where you have an active TransactionScope and the insertion is huge (4000+). It can ...
- 9,530
796
votes
21
answers
680k
views
There is already an open DataReader associated with this Command which must be closed first
I have this query and I get the error in this function:
var accounts = from account in context.Accounts
from guranteer in account.Gurantors
select new AccountsReport
...
- 27.7k
731
votes
47
answers
554k
views
MetadataException: Unable to load the specified metadata resource
All of a sudden I keep getting a MetadataException on instantiating my generated ObjectContext class. The connection string in App.Config looks correct - hasn't changed since last it worked - and I've ...
- 15.5k
687
votes
23
answers
282k
views
SqlException from Entity Framework - New transaction is not allowed because there are other threads running in the session
I am currently getting this error:
System.Data.SqlClient.SqlException: New transaction is not allowed because there are other threads running in the session.
while running this code:
public class ...
- 25.1k
656
votes
10
answers
355k
views
Code-first vs Model/Database-first [closed]
What are the pros & cons of using Entity Framework 4.1 Code-first over Model/Database-first with EDMX diagram?
I'm trying to fully understand all the approaches to building data access layer ...
- 45.8k
604
votes
22
answers
407k
views
Unable to update the EntitySet - because it has a DefiningQuery and no <UpdateFunction> element exist
I am using Entity Framework 1 with .net 3.5.
I am doing something simple like this:
var roomDetails = context.Rooms.ToList();
foreach (var room in roomDetails)
{
room.LastUpdated = ...
- 9,291
600
votes
35
answers
462k
views
No Entity Framework provider found for the ADO.NET provider with invariant name 'System.Data.SqlClient'
After downloading the EF6 by nuget and try to run my project, it returns the following error:
No Entity Framework provider found for the ADO.NET provider with invariant name 'System.Data.SqlClient'....
- 6,205
567
votes
18
answers
542k
views
EF Migrations: Rollback last applied migration?
This looks like a really common task, but I can't find an easy way to do it.
I want to undo the last applied migration. I would have expected a simple command, like
PM> Update-Database -...
- 35.1k
520
votes
10
answers
395k
views
Entity Framework - Include Multiple Levels of Properties
The Include() method works quite well for Lists on objects. But what if I need to go two levels deep? For example, the method below will return ApplicationServers with the included properties shown ...
- 33.9k
461
votes
28
answers
498k
views
Conversion of a datetime2 data type to a datetime data type results out-of-range value
I've got a datatable with 5 columns, where a row is being filled with data then saved to the database via a transaction.
While saving, an error is returned:
The conversion of a datetime2 data type ...
- 5,354
454
votes
34
answers
314k
views
Entity Framework Provider type could not be loaded?
I am trying to run my tests on TeamCity which is currently installed on my machine.
System.InvalidOperationException:
The Entity Framework provider type
'System.Data.Entity.SqlServer....
- 9,288
449
votes
10
answers
233k
views
Why use ICollection and not IEnumerable or List<T> on many-many/one-many relationships?
I see this a lot in tutorials, with navigation properties as ICollection<T>.
Is this a mandatory requirement for Entity Framework? Can I use IEnumerable?
What's the main purpose of using ...
- 12k
445
votes
5
answers
187k
views
Entity Framework VS LINQ to SQL VS ADO.NET with stored procedures? [closed]
How would you rate each of them in terms of:
Performance
Speed of development
Neat, intuitive, maintainable code
Flexibility
Overall
I like my SQL and so have always been a die-hard fan of ADO.NET ...
- 13.3k
444
votes
9
answers
119k
views
One DbContext per web request... why?
I have been reading a lot of articles explaining how to set up Entity Framework's DbContext so that only one is created and used per HTTP web request using various DI frameworks.
Why is this a good ...
- 11.2k
431
votes
9
answers
227k
views
What are the best practices for using a GUID as a primary key, specifically regarding performance? [closed]
I have an application that uses GUID as the Primary Key in almost all tables and I have read that there are issues about performance when using GUID as Primary Key. Honestly, I haven't seen any ...
- 14.8k
424
votes
14
answers
296k
views
The entity cannot be constructed in a LINQ to Entities query
There is an entity type called Product that is generated by entity framework.
I have written this query
public IQueryable<Product> GetProducts(int categoryID)
{
return from p in db.Products
...
- 20k
424
votes
20
answers
387k
views
Introducing FOREIGN KEY constraint may cause cycles or multiple cascade paths - why?
I've been wrestling with this for a while and can't quite figure out what's happening. I have a Card entity which contains Sides (usually 2) - and both Cards and Sides have a Stage. I'm using EF ...
- 12.6k
413
votes
38
answers
512k
views
Error message 'Unable to load one or more of the requested types. Retrieve the LoaderExceptions property for more information.'
I have developed an application using Entity Framework, SQL Server 2000, Visual Studio 2008 and Enterprise Library.
It works absolutely fine locally, but when I deploy the project to our test ...
- 26.7k
409
votes
12
answers
417k
views
How to compare only Date without Time in DateTime types?
Is there a way to compare two DateTime variables but to disregard the Time part.
The app stores items in the DB and adds a published date. I want to keep the exact time but still be able to pull by ...
- 10.4k
396
votes
27
answers
431k
views
How do I delete multiple rows in Entity Framework (without foreach)
I want to delete several items from a table using Entity Framework. There is no foreign key / parent object, so I can't handle this with OnDeleteCascade.
Right now I'm doing this:
var widgets = ...
- 52.7k
394
votes
10
answers
416k
views
Entity Framework Timeouts
I am getting timeouts using the Entity Framework (EF) when using a function import that takes over 30 seconds to complete. I tried the following and have not been able to resolve this issue:
I added ...
- 14.8k
376
votes
18
answers
306k
views
Reset Entity-Framework Migrations
I've mucked up my migrations, I used IgnoreChanges on the initial migration, but now I want to delete all my migrations and start with an initial migration with all of the logic.
When I delete the ...
- 18k
376
votes
2
answers
298k
views
Ignoring a class property in Entity Framework 4.1 Code First
My understanding is that the [NotMapped] attribute is not available until EF 5 which is currently in CTP so we cannot use it in production.
How can I mark properties in EF 4.1 to be ignored?
UPDATE: ...
- 14.4k
367
votes
4
answers
307k
views
Using Transactions or SaveChanges(false) and AcceptAllChanges()?
I have been investigating transactions and it appears that they take care of themselves in EF as long as I pass false to SaveChanges() and then call AcceptAllChanges() if there are no errors:
...
- 20.8k
366
votes
25
answers
388k
views
Entity Framework. Delete all rows in table
How can I quickly remove all rows in the table using Entity Framework?
I am currently using:
var rows = from o in dataDb.Table
select o;
foreach (var row in rows)
{
dataDb.Table.Remove(...
- 4,049
357
votes
45
answers
411k
views
Entity Framework: "Store update, insert, or delete statement affected an unexpected number of rows (0)." [closed]
I am using Entity Framework to populate a grid control. Sometimes when I make updates I get the following error:
Store update, insert, or delete statement affected an unexpected number of rows (0). ...
- 3,957
344
votes
6
answers
295k
views
What difference does .AsNoTracking() make?
I have a question regarding the .AsNoTracking() extension, as this is all quite new and quite confusing.
I'm using a per-request context for a website.
A lot of my entities don't change so don't ...
- 11.1k
339
votes
17
answers
325k
views
Validation failed for one or more entities while saving changes to SQL Server Database using Entity Framework
I want to save my Edit to Database and I am using Entity FrameWork Code-First in ASP.NET MVC 3 / C# but I am getting errors. In my Event class, I have DateTime and TimeSpan datatypes but in my ...
- 4,023
336
votes
17
answers
220k
views
Entity Framework: There is already an open DataReader associated with this Command
I am using Entity Framework and occasionally i will get this error.
EntityCommandExecutionException
{"There is already an open DataReader associated with this Command which must be closed first."}
...
- 24.4k
329
votes
20
answers
899k
views
How to update record using Entity Framework 6?
I am trying to update a record using EF6. First finding the record, if it exists, update.
Here is my code:
var book = new Model.Book
{
BookNumber = _book.BookNumber,
BookName = _book.BookName,...
- 4,277
329
votes
7
answers
154k
views
Create code first, many to many, with additional fields in association table
I have this scenario:
public class Member
{
public int MemberID { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public virtual ICollection&...
- 3,293
326
votes
12
answers
264k
views
Unique Key constraints for multiple columns in Entity Framework
I'm using Entity Framework 5.0 Code First;
public class Entity
{
[Key, DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public string EntityId { get; set;}
public int FirstColumn { get;...
- 16.7k
323
votes
11
answers
311k
views
Entity Framework Core add unique constraint code-first
I can't find way to add a unique constraint to my field with using attribute:
public class User
{
[Required]
public int Id { get; set; }
[Required]
// [Index("IX_FirstAndSecond", 2, ...
- 3,285
319
votes
7
answers
226k
views
Entity Framework Code First - two Foreign Keys from same table
I've just started using EF code first, so I'm a total beginner in this topic.
I wanted to create relations between Teams and Matches:
1 match = 2 teams (home, guest) and result.
I thought it's ...
- 5,945
307
votes
22
answers
593k
views
How to call Stored Procedure in Entity Framework 6 (Code-First)?
I am very new to Entity Framework 6 and I want to implement stored procedures in my project. I have a stored procedure as follows:
ALTER PROCEDURE [dbo].[insert_department]
@Name [varchar](100)
...
- 3,373
300
votes
9
answers
108k
views
Should services always return DTOs, or can they also return domain models?
I'm (re)designing large-scale application, we use multi-layer architecture based on DDD.
We have MVC with data layer (implementation of repositories), domain layer (definition of domain model and ...
- 5,935
296
votes
9
answers
332k
views
Non-static method requires a target
I have a controller action that works fine on Firefox both locally and in production, and IE locally, but not IE in production. Here is my controller action:
public ActionResult MNPurchase()
{
...
- 14.4k
290
votes
19
answers
255k
views
Decimal precision and scale in EF Code First
I'm experimenting with this code-first approach, but I'm find out now that a property of type System.Decimal gets mapped to a sql column of type decimal(18, 0).
How do I set the precision of the ...
- 17.2k
281
votes
11
answers
177k
views
Entity Framework: One Database, Multiple DbContexts. Is this a bad idea? [closed]
My impression to date has been that a DbContext is meant to represent your database, and thus, if your application uses one database, you'd want only one DbContext.
However, some colleagues want to ...
- 8,130
277
votes
3
answers
124k
views
What does principal end of an association means in 1:1 relationship in Entity framework
public class Foo
{
public string FooId{get;set;}
public Boo Boo{get;set;}
}
public class Boo
{
public string BooId{get;set;}
public Foo Foo{get;set;}
}
I was trying to do this in ...
- 4,110
277
votes
4
answers
151k
views
Entity Framework and Connection Pooling
I've recently started to use the Entity Framework 4.0 in my .NET 4.0 application and am curious about a few things relating to pooling.
Connection pooling as I know is managed by the ADO.NET data ...
- 146k
271
votes
19
answers
365k
views
Entity Framework 6 Code first Default value
is there "elegant" way to give specific property a default value ?
Maybe by DataAnnotations, something like :
[DefaultValue("true")]
public bool Active { get; set; }
Thank you.
- 2,721
269
votes
30
answers
283k
views
No connection string named 'MyEntities' could be found in the application config file
I am using entity framework and ASP.NET MVC 4 to build an application
My solution is split into two projects;
A class library that includes my data model (.edmx) file and a few custom interfaces
The ...
- 3,559
268
votes
10
answers
147k
views
Using MySQL with Entity Framework [closed]
Can't find anything relevant about Entity Framework/MySQL on Google so I'm hoping someone knows about it.
- 2,893
256
votes
12
answers
180k
views
"A lambda expression with a statement body cannot be converted to an expression tree"
In using the EntityFramework, I get the error "A lambda expression with a statement body cannot be converted to an expression tree" when trying to compile the following code:
Obj[] myArray = objects....
- 58k
252
votes
15
answers
230k
views
How to pass parameters to the DbContext.Database.ExecuteSqlCommand method?
Let's just suppose I have a valid need for directly executing a sql command in Entity Framework. I am having trouble figuring out how to use parameters in my sql statement. The following example (not ...
- 74.9k