I'm using asp.net mvc, linq2sql, iis7 and sqlserver express 2008.
I get these intermittent server errors, primary key conflicts on insertion. I'm using a different setup on my development computer so I can't debug. After a while they go away. Restarting iis helps. I'm getting the feeling there is cache somewhere that I'm not aware of. Can somebody help me sort out these errors?
Cannot insert duplicate key row in object 'dbo.EnquiryType' with unique index 'IX_EnquiryType'.
Edits regarding Venemos answer
Is it possible that another application is also accessing the same database simultaneously?
Yes there is, but not this particular table and no inserts or updates. There is one other table with which I experience the same problem but it has to do with a different part of the model.
How often an in what context do you create a new DataContext instance?
Only once, using the singleton pattern.
Are the primary keys generated by the database or by the application?
Database.
Which version of ASP.NET MVC and which version of .NET are you using?
RC2 and 3.5.
Two guesses for you:
1) If you've got a singleton DataContext, wouldn't that mean it's shared by all threads?
The MSDN reference for DataContext says an instance is "designed to last for one unit of work" and typically created "at method scope or as a member of short-lived classes".
I'd try moving away from the singleton pattern and creating a new context each time it is needed.
2) When you say your keys are generated by the database, is that through Identity fields, or some kind of "select max + 1" pattern? If not by an identity, then you may have concurrent connections obtaining the same "next" key value. Check your transaction isolation levels.
EDIT - following on from comment
Are you sure that the index violation is on the primary key? Using SQL Server Management Studio, primary keys are normally given a PK_ prefix, and IX_ is used for further indexes. Check the fields which go to make up "IX_EnquiryType" and ensure it's not just a rare logic problem that's causing your problems.
Well, it can be because of many reasons. I'll give you some questions. Please edit your question with the info about these, and it will be much more straightforward for us to help you.
Is it possible that another application is also accessing the same database simultaneously?
This would be the most likely reason. I experienced this, too.
How often an in what context do you create a new DataContext instance?
The best way would be to create a new one per request.
Are the primary keys generated by the database or by the application?
Which version of ASP.NET MVC and which version of .NET are you using?
Related
So I want to build an application with MVC 4 and Entity Framework 5. I've build simple applications before, but now I need some security around my current effort... I have some confusion / questions that I was hoping someone could answer;
First... Using the MVC 4 Internet Application Template it implements SimpleMembershipProvider. I have read every primary article about modification, implementation... However, this uses a Code-First implementation...
Problem: I have an existing database that I would like to import the scheme for to an EDMX database first approach... How do I implement the MVC 4 Simple membership provider when my database ties tightly and directly into the user table (userid)?... I know I can use my own user table as long as i designate the userid and username fields as documented... Will this affect the provider, or the existing "AccountController" code? Will these need to be modified?
Second, what I am looking for is a workflow with this architecture... I am "old school" mostly database first approach... My project is a huge WIP (work in progress). I have a foundation, but will need to expand as needed... Can someone provide some insight into database first vs other approaches when there will be quite a bit of change management occurring?
you can still use Code First to map to an existing database. You may need to explicitly map properties to table columns because the mappings do not follow the default conventions, but that doesn't prevent you from using Code First.
When transitioning from DB first to another mindset. Focus on how the objects interact with each other. then, at some point you will save the state of the objects after they interacted. This is where the ORM comes into play. detects changes and executes the necessary SQL statements to persist the current state of the objects.
Think of the database as just another storage container. In theory it could be replaced by another persistent storage mechanism (document db, file, persistent hash table, in memory list, etc.). In reality it's not that simple, but the idea of treating the DB as just a simple storage container helps to break away from the monolithic database concept that is/was ingrained into most devs.
But don't loose perspective of the design either. If it's a simple forms-over-data app where you will be adding features in the future than keep the design simple. than don't try to totally abstract the DB away. you know it's there and the relationship to the UI is almost 1:1, so take advantage of that.
In it's simplest form separation of concerns can be achieved by using the MVC controller to manage the interaction between the model (mapped to the DB via ORM) and the view (razor templates) my personal preference is to keep ORM out of the views so I typically query the database, map the domain model to a viewmodel and then pass the viewmodel to the view.
Again if it's a simple application and screens map directly to the database than viewmodel are probably overkill.
I'm working on a project already started by several developers before me. One thing in particular bothers me is that they have single entity split in two databases.
Entity is called Tracker.
First database is called ConfigBase, and it has table named Trackers that has TrackerId along with it's attributes.
Second database is called StoreBase, and it also has table named Trackers, whose elements have matching TrackerId as it is in the first base.
Moreover, to have things even more complicated, when you access specific tracker in ConfigBase, you gain SQL server name and credentials that allow you to access it in StoreBase.
Now all this isn't too much complicated if you use plain old ADO.NET. But as my task is to raise entire solution to newest EF 4.3.1, I'm having troubles maintaining consistency of my entity. Half of things related to Tracker entity are in ConfigBase and the other half in StoreBase, and usually I have to get both to get some result.
Is there any solution to this that does not involve virtual merge on database level. I'm looking for a solution that can be done with Code First modelling.
Thanks in advance!
No there is no solution provided out of the box because EF itself is even not able to use more than one database per context. So you will either merge your databases or you will access each database separately (with separate Tracker entity per database) and merge data somehow in your application.
For my ASP.NET MVC app, I just find dealing with unique-identifiers harder, so I have added my own field to ASPNET_USERS table - UserIdInt (which is actually a bigint!) So most of user operations use userIdInt as reference.
Anyway, I am debating between two approaches:
1)When a user logs in, look up from the database and store the userIdInt in a session variable and any-time session variable slips away, re-look it up and put it back in session variable. (It's okay to use sessions in MVC app, right?)
2)Any time an operation needs to be performed, simply pass userName to database and take care of UserIdInt at database side by doing joins and such on ASPNET_Users table any time an operation from user needs to be performed.
I am heavily leaning towards 1)... but I want to make sure I am on right track.
I asked this question on Serverfault first, but I was told to ask this question here.
progtick,
you may be far better looking into the use of custom profile providers as this would allow you to leave the aspnet_* tables as is (which is a good idea in case a later version of sqlserver changes how they operate) plus offer the additional bebnefit of having a multitude of additonal profile related properties availabale to your application. i can't overstate enough the benefits in going down this track as i've found it very useful to have such an approach in both my standard asp.net apps as well as my mvc ones.
you can get a feel for what's involved in this by looking thro a couple of these links:
here's one on SO for starters:
Implementing Profile Provider in ASP.NET MVC
and one from my old mate, lee dumond:
http://leedumond.com/blog/asp-net-profiles-in-web-application-projects/
hope this helps
An alternative approach is to alter the forms authentication ticket to add your unique id to the data stored in the cookie. Then, by implementing a custom IPrincipal you can have your unique id available anywhere that the User object is available.
I want to develop an ASP.Net MVC application with EF4 Model First design and only generate the actual database much later, ideally at the end of the project.
Based on some of the ideas here:
http://elegantcode.com/2009/12/15/entity-framework-ef4-generic-repository-and-unit-of-work-prototype/
I want to create something like an InMemoryObjectContext for testing and development and use IOC to switch to the SQL Server implamentation (EF generated) for UAT and production.
Is this wise?
Is it possible? If so, does anyone have any suggestions?
Does EF always need an underlying database in order to track changes, commit etc?
I've tried creating a model first but as soon as I add properties I get the following errors:
Error 2062: No mapping specified for instances of the EntitySet and AssociationSet in the EntityContainer Model1Container.
and the warning:
Running transformation: Please overwrite the replacement token '$edmxInputFile$' with the actual name of the .edmx file you would like to generate from.
The error doesn't stop the application running but worries me. I'm very very new to EF so I apologize if this is way off the mark or a dumb question. I'm hoping to get some good advice while I sit for the next few days and watch videos and read articles.
Thanks
Davy
At the very least you need mapping information "filled in". You can fill these fields with nonsense if you don't want to work against the underlying database.
If your doing Model first, right click on the designer canvas and select, "Generate Database from Model". This will automatically create convention based mappings for you without defining tables and columns. You don't even need a valid db connection to do this.
I'm just starting a new project on ASP.NET MVC and this will be the first project actually using this technology. As I created my new project with Visual Studio 2010, it created to my sql server a bunch of tables with "aspnet_" prefix. Part of them deal with the built-in user accounts and permission support.
Now, I want to keep some specific information about my users. My question is "Is it a good practice changing the structure of this aspnet_ tables, to meet my needs about user account's information?".
And as i suppose the answer is "No." (Why exactly?), I intend to create my own "Users" table. What is a good approach to connect the records from aspnet_Users table and my own custom Users table.
I want the relationship to be 1:1 and the design in the database to be as transparent as possible in my c# code (I'm using linq to sql if it is important). Also, I don't want to replicate the usernames and passwords from the aspnet_ tables to my table and maintain the data.
I'm considering using a view to join them. Is this a good idea?
Thanks in advance!
EDIT: From the answer, I see that I may not be clear enough, what I want. The question is not IF to use the default asp.net provider, but how to adopt it, to my needs.
I would create custom membership provider and omit those aspnet_x tables completely. I've seen what happens when one joins these tables and custom ones with nhibernate mappings - pure nightmare.
If you are choosing to use the Membership API for your site, then this link has information regarding how to add extra information to a user.
I was faced with the same scenario recently and ended up ditching the membership functionality and rolled my own db solution in tandem with the DotNetOpenAuth library.
Using the membership system in asp.net has its advantages and drawbacks. It's easy to start, because you don't have to worry about validation, user registration, resetting passwords. (Be careful if you plan to modify the table structures, you will have to change them in the views/store procedures generated
However there are drawbacks to using Membership
You will have to maintain 2 separated systems, because the Membership API has restrictions, for example, you cannot perform operations inside a transaction with the membership api. (Unless you use TransactionScope i think, but you don't have other choices).
A valid alternative would be to implement your own security validation routines, and using FormsAuthentication. This way you will have total control over your users tables, and remove dependency to the membership API.