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I've read somewhere that if I use SMO files from the latest SQL server version , these can work with lower versions too.
Is this true ?
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Yes 
Bastard Programmer from Hell 
If you can't read my code, try converting it here[^]
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Hello !
I'm using vb.net 2013 , SQL server 2008 R2 and entity Frameowrk 6.
I have a situation where on the database , I need to have a foreign key refer the primary key on the same Table.
Employe Table
------------
ID
Name
Position
Manager ID
ID is the primary key , Manager ID is the foreign key , and as the manager is also an employee on the same table , this foreign key refer to the primary key ID on the table employee. But several employees can have the same Manager ID.
I want to know if this is possible and safe to use on sql server and also to work with it on Entity Framework.
Thank you !
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desanti wrote:
I want to know if this is possible and safe to use on sql server and also to work with it on Entity Framework.
That's a rather common thing to do. Without knowing much EF, I'm going to say that it is possible and safe.
Bastard Programmer from Hell
If you can't read my code, try converting it here[^]
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A structure known as a pig's ear!
Recursive Relationships
=========================================================
I'm an optoholic - my glass is always half full of vodka.
=========================================================
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Hello !
On Visual studio 2017 , is there possible to use Entity framework 6 , with Database first ?
Because i can't find a way to start a such project.
Thank you !
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Google for "entity framework 6 database first tutorial". The version of Visual Studio does not matter.
Before you dive into a project using EF, Google for "entity framework database first vs code first", to understand what the differences and restrictions on what you can do are going to be for each method.
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Thank you !
I know how to use and work with Entity framework and EF6 with database first.
I want to use it as I've used on Visual studio 2013.
But on Visual studio 2017 , I can't find a way how to start a project with EF6 and Database first.
It seems that VS 2017 is using only Entity framework Core and dropped the support for EF6 ? Or i'm wrong ?
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Sigh ... A little Google goes a long way.
Right-click your project, pick Add --> New Item. Click on Data in the left pane. Double-click ADO.NET Entity Data Model. Follow the wizard.
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desanti wrote: It seems that VS 2017 is using only Entity framework Core and dropped the support for EF6 ? Or i'm wrong ?
You're wrong. I'm using EF6 (not Core) in VS2017, and it's supported perfectly well. You just need to add a reference to the NuGet package called "EntityFramework".
(EF Core is "the future", and will receive the bulk of Microsoft's attention from now on. But there are still a few things that it doesn't support.)
"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer
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Richard Deeming wrote: EF Core is "the future", and will receive the bulk of Microsoft's attention from now on
Yeah, there's an upgrade I'm not looking forward to. Hopefully we don't have a ton of work to do on a web app that we spent two years writing, using EF 6.x.
Richard Deeming wrote: ut there are still a few things that it doesn't support
...and there's the reason we haven't dug into it yet.
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And you just know that two months after upgrading, Microsoft will announce that it's being replaced with a newer, shinier version, and the version you've just upgraded to is no longer being maintained. 
"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer
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Man, you speak the truth!
When we started the project it was a about a month before 6.0 came out, so we reworked from 5 to 6.0, then migrations to every 6.x version there is.
Don't get me started on MVC.
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Richard Deeming wrote: (EF Core is "the future", and will receive the bulk of Microsoft's attention from now on. But there are still a few things that it doesn't support.)
Right up until they DEPRECATE the bloody thing and come up with some new insanity for us to work with.
AAAAAaaaahhhhhhhhhhhhhhhh pft!
Never underestimate the power of human stupidity
RAH
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Hi,
I am given a hard copy consent form that needs to be in a web page including an area for signature. What's the best way to accomplish this?
Thanks
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Hello !
I'm using vb.net 2013 , Entity framework 6 and SQL server 2008R2.
I'm trying to delete from child entities , and this does not work. But if I try to delete directly from context , this works.
In my database I have 2 tables Students and Result
This is my code that does not work :
Dim context as Myentities=New myentities.
Dim s as student.
Dim lresult as new list (of result)
s=context.students.where(Function(t1) t1.value>5).Tolist.first
lresult=(from t in s.results where t.vl2=7 select t).Tolist
for each rs as result in lresult
if rs.vl3=11 then s.results.remove(rs)
Next
Context.savechanges
This code produce an error on the last line( context.savechanges ) :
An unhandled exception of type 'System.InvalidOperationException' occurred in EntityFramework.dll
Additional information: The operation failed: The relationship could not be changed because one or more of the foreign-key properties is non-nullable. When a change is made to a relationship, the related foreign-key property is set to a null value. If the foreign-key does not support null values, a new relationship must be defined, the foreign-key property must be assigned another non-null value, or the unrelated object must be deleted.
But if I change the line that delete the item , like below , this works :
Dim context as Myentities=New myentities.
Dim s as student.
Dim lresult as new list (of result)
s=context.students.where(Function(t1) t1.value>5).Tolist.first
lresult=(from t in s.results where t.vl2=7 select t).Tolist
for each rs as result in lresult
if rs.vl3=11 then context.results.remove(rs)
Next
Context.savechanges
Why my first code does not work ?
Thank you !
modified 14-Feb-18 14:33pm.
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Entity Framework Gotchas – Strategies for Orphaned Child Objects[^]
When you call s.results.remove, you're clearing the parent relationship from the entity, but not marking it for deletion.
When you call context.results.remove, you're marking the entity for deletion.
NB: You can clean up your code and improve the performance by not calling ToList when you only want a single object.
s = context.Students.Where(Function(t1) t1.Value > 5).ToList().First()
s = context.Students.Where(Function(t1) t1.Value > 5).First()
s = context.Students.First(Function(t1) t1.Value > 5)
You should also be aware that First will throw an exception if there are no matching records. You might want to consider using FirstOrDefault instead, which will return Nothing if there are no matching records.
"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer
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But why when I add a child object I can do directly :
s.results.add(Myobject)
And for the deletion I can't do that as you've said but I should call context.results.remove(Myobject)
So entity framework has different logic for adding and deleting ?
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When you add an entity to the s.results collection, EF sees that it doesn't already exist in the database, and marks it as "Added". It will then insert that record into the database when you save the changes.
When you remove an entity from the s.results collection, EF has no way of knowing whether you wanted to delete the entity from the database, or just remove the connection between the two entities. To avoid inadvertent data-loss, it just tries to remove the connection. To delete it from the database, you have to remove it from the context.results set instead.
"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer
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Hello !
I'm using VB.net 2013 , Entity Framework 6 with sql server 2008R2.
I have a situation where I've made a lot of changes in different entities.
And at the end , I've made a question if the user want to save to database or no .
If yes , I call Savechanges and all the changes are saved.
But if no , I want to undo all the changes made.
Is there any easy way to do this ? I mean , I've found several articles on internet that suggest to undo one by one all the changes.
But is there any easy way , because I don't want to undo specific changes , but all the changes.
Thank you !
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Using a simple DAL (not EF) I simply reload the view to get the actual from the database.
Never underestimate the power of human stupidity
RAH
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If you haven't saved the changes, all you have to do is .Dispose() the DbContext instance. The changes die with it.
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I've called
mycontext.dispose.
But after I ca have this code :
Mycontext=New MyEntities
Mycontext.savechanges
and all the changes that I've made before disposing , are saved !!!!!
Why ???
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