EF is so widely used staff but I don't realize how I should use it. I met a lot of issues with EF on different projects with different approaches. So some questions brought together in my head. And answers leads me to use pure ado.net with stored procedures.
So the questions are:
How to deal with EF in n-tier application?
For example, we have some DAL with EF. I saw a lot of articles and projects that used repository, unit of work patterns as some kind of abstraction for EF. I think such approach kills most of benefits that increase development speed and leads to few things:
remapping of EF load results in some DTO that kills performance(call some select to get table data - first loop, second loop - map results to some composite type generated by ef, next - filter mapped data using linq and, at last, map it to some DTO). Exactly remapping to DTO is killer of one of the biggest efs benefit;
or
leads to strong cohesion between EF (and it's version) and app. It will be something like 2-tier app with dal and presentation with bll or dal with bll and presentation. I guess it's not best practice. And the same loading process as we have for previous thing except mapping, so again performance issue raised up. We could try to use EF as DAL without any abstraction under them. But we will get similar issues in some other way.
Should I use one context per app\thread\atomic operation? Using approach - one context per app\thread may slightly increase performance and possibilities to call navigation properties, but we meet another problem - updating this context and growing loaded data in context, also I'm not sure about concurrency with one dbcontext per app\thread. Using context per operation will lead us to remapping EF results to our DTO's. So you see that we again pushed back to question no.1.
Could we try to use EF + stored procedures only? Again we have issues from previous questions. What is the reason to use EF if the biggest part of functionality will not be used?
So, yes EF is great to start project. It so convenient when we have few screens and crud operations.
But what next?
All this text is just unsorted thoughts. I know that pure ado.net will lead to another kind of challenges.
So, what is your opinion about this topic?
By following the naming conventions , you will find it's called : ADO.NET Entity Framework , which means that Entity Framework sits on top of ADO.NET so it can't be faster , It may perform both in equal time , but let's look at EF provides :
You will no more get stuck with writing queries without any clue about if what you're writing is going to compile or not .
It makes you rely on C# or your favorite .NET language on writing your own data constraints that you wish to accept from the target user directly inside your model classes .
Finally : EF and LINQ give a lot of power in maintaining your applications later .
There are three different models with the Entity Framework : Model First , Database First and Code First get to know each of 'em .
-The Point about killing performance when remapping is on process , it's because that on the first run , EF loads metadata into memory and that takes time as it builds in-memory representation of model from edmx file.
ADO. Net is an object oriented framework that allows you to interact with database system (SQL, Oracle, etc).
Entity framework is a techniques of manipulating data in databases like (collection of queries (inert table name , select * from like this )).
it is uses with LINQ.
Entity Framework is not efficient in any case as in most tools or toolboxes designed to achieve 'faster' results.
Access to database should be viewed as a separate tier using store procedures as the interface. There is no reason for any application to have more than absolutely require CRUD operations. Less is more principle. Stored procedures are easy to write, secure, maintain and is de facto fastest way. It's easy to write tools to generate desired codes for POCO and DbContext through stored procedures.
Application well designed should have a limited numbers of connection strings to database and none of which should be the all mighty God. Using schema to support connection rights.
Lazy loading are false statements added to solve a problem that should never exist and introduced with ORM and its plug and play features. Data should only be read when needed. Developers should be responsible to implement this logic base on application context.
If your application logic has a problem to maintain states, no tool will help. It will in fact, make it worse by cover up the real problem until it's too late.
Database first is the only solution for a well designed application. Civilization realized long time ago the important of solid aqueduct and sewer system. High level code can and will be replaced anytime but data stays. Rewrite an entire application is matter of days if database is well designed.
Applications are just glorified database access. Still true in most cases.
This is my conclusion after many years in business applications debugging through codes produced by many different tools or toolboxes. The faster results advertised are not even close to cover the amount of time/energy wasted later trying to clean up the mess. Performance issues are rarely if not ever caused by high demand but the sum of all 'features' added through unusable tools.
ADO.NET provides consistent access to data sources such as SQL Server and XML, and to data sources exposed through OLE DB and ODBC. Data-sharing consumer applications can use ADO.NET to connect to these data sources and retrieve, handle, and update the data that they contain.
Entity Framework 6 (EF6) is a tried and tested object-relational mapper (O/RM) for .NET with many years of feature development and stabilization. An ORM like EF has the following advantage
ORM lets developers focus on the business logic of the application thereby facilitating huge reduction in code.
It eliminates the need for repetitive SQL code and provides many benefits to development speed.
Prevents writing manual SQL queries; & many more..
In an n-tier application,it depends on the amount of data your application is handling and your database is managing. According to my knowledge DTO's don't kill performance. They are data container for moving data between layers and are only used to pass data and does not contain any business logic. They are mostly used in service classes.See DTO.
One DBContext is always a best practice.
There is no such combination of EF + SP(Stored Procedure) as per my knowledge. If you wish to use an ORM like EF and an SP at the same time try micro-ORMs like Dapper,BLToolkit, etc..It was build for that purpose and is heck lotta fast than EF. Here is a good article on Dapper ORM.
Here is a related thread on a similar topic: What is the difference between an orm and ADO.net?
Related
we are at the beginning of a new project, which will replace a legacy project. The legacy one is written in .Net Framework 4.0 (SOA with WCF) + SQL Server. The connection with SQL is made by ADO.Net + stored procedures. There is a structural mistake by having most of the logic on the stored procedures, and on top of that, it is a monolytic.
The new project will be made with .Net 6 APIs and in some cases, it will have SQL Server as well, for operational data.
So, looking at the new product the question was raised: should we move from ADO.Net to EF? This is tempting since it reduces the development effort, but performance is a concern.
Taking a look at the technical must haves:
Get the product to be as fast as possible (performance is a concern)
The new project is expected to live at least for the next 15 years
Operations are executed against tables with 30 to 50 million records
We must be able to run operations against the regular database, but also against the readonly one (AlwaysOn)
We must be able to perform some resiliency policies such as retries in case of deadlocks
We don't have much room for changes if we choose one path and somewhere along the way we realize we should had gone with the other option
Quite honestly, IMHO, based on our tech requirements I feel should move forward with ADO.Net + Stored procedures (without any business logic) + some sort of package that translates the SQL results to my objects in a fast manner, but I'd like to give EF a shot, at least on this stage of the process where we are investigating possibilities.
I'd like to gather if possible opinions, specially if there is someone out there that went to EF with requirements as similar as ours, or someone who didn't go to EF or had to change from EF to ADO.Net somewhere along the way.
Thanks.
The only thing in your requirements that could support using ADO.NET over EF is
Get the product to be as fast as possible (performance is a concern)
Which is a nonsense requirement, as you can always write more code and make things more complex to make things marginally faster. You need a real performance requirement so you can measure different approaches.
I'm developing C# Desktop application with using code first C# entity-framework technology. I need to use layered architecture with these layers on it.
1.Entity Layer - for code first db creation
2.Data Access Layer - for accessing db and all the db related methods are here
3.Business Logic layer - for connecting interface with data access layer
4.Presentation Layer - for interface designing
on getting data from database, it takes a while to load. is there any way to fix it...?
My project manager Prof said that it's because of the layered architecture....
Without having any idea on your model it is impossible to say why data retrieval is slow. EF is somewhat slower than other ORM frameworks on .NET but it works fine. You should start analysing your model. Also, remember that you have a database behind your model. Users of ORM tools have tendency to forget about this. You can use something like EF Profiler to see the queries you are sending to your database server. This kind of tools is a must when using ORM over more or less complex model.
One typical issue is SELECT N+1 problem when you fetch an entity that has a collection of other entities, the collection is proxied and you start to loop through it, your child entities are lazy loaded one by one, issuing at least as many queries as you have those child entities. In this case eager fetchig is the key solution. But, again, you provided no details, so you have to figure out the issue yourself. And the problem is not EF as such and not layered architecture.
Please excuse the noob question as I am new to integrating data with my applications. I've tried to find answers on the net, but not there yet.
I have an application I'm developing in C# on VS2010 which requires data in/out from a database. I am trying to figure out if its a DataSet or Entity Data Model I need to use when setting up a data source. My understanding was that it was the EDM which allowed me to treat tables/fields in a database as objects, but somehow it looks like I can do that with a DataSet too.
Some sources explain that a DataSet makes a cached copy of the Database which can then be manipulated.
Essentially my question is which should I use and what are the (dis)advantages of one over the other.
You have several options open to you when it comes to storing and retrieving data to/from a database:
At the very simplest level, use ADO.NET to open a connection to the DB, create a command and execute it. If you expect results back (i.e. SELECT ...) then you could call the command's ExecuteReader(...). Working in this manner results in very quick execution and the minimum of overhead, but you have to do more of the heavy lifting. If your app is simple, this is probably a good way to go. If your app is, or is likely to be more complex, you may want to consider other options...
ADO.NET DataSets are a reasonable DB IO mechanism, particularly for reading data from a DB. However, they can be a little cumbersome when trying to update the DB.
You could use an Object-Relational Mapper (ORM) like nHibernate or Entity Framework, but, frankly, that often results in your learning curve increasing dramatically while you figure out how to plug together the moving parts and make them work well together.
You might also consider a new variant of Entity Framework called Code First (CF): This allows you to pretty much design your code and CF will generate your EDM and handle the majority of the DB operations required for you to build your system. Scott Hanselman wrote up a nice intro into EF CF.
Having used practically every DB API and ORM on Windows over the last 20+ years, I am delighted with how CF is shaping up! EF 4.3 that shipped just a couple of weeks ago includes some key new improvements to CF including migrations which allow you to handle changes to your DB schema as it evolves. I've build 3-4 systems using EF CF over the last couple of months and am very happy - it's my favorite relational database IO mechanism at present.
If you want to really get into EF CF, I strongly recommend Julia Lerman's book EF CF - it's a short, nicely written, very useful guide that should take you no more than a day or two to work through the main sections of.
Hope this helps.
If you add a LocalDB data source to your project (because you want a small local database file) then when the Data Source Configuration Wizard pops up, it explicitly asks you whether you want to use a Dataset or Entity Data Model database model. Is this the situation you were facing? That was the problem I had that brought me to this entry.
There is no question that for an enterprise class application, or a website, you would want to investigate ADO.NET or an ORM, but it doesn't help answer this question, which has to do with what are the differences between choosing Dataset vs Entity Data Model in the wizard.
Essentially, Entity Data Model is the more recent technology. If you are unfamiliar with Dataset, then this is probably not the time to start using it.
If you're asking what are the pros and cons for ADO.NET (DataSet) vs EntityFramework (Entity Data Model) then there is a discussion that may help at ADO.NET Entity Framework or ADO.NET
EF will get you up and running pretty quickly but in my (very limited) experience its been a pain to maintain.
What is it that has determined that these are your only two options? There are far more available to you including many ORMs.
If your application is supporting a business application than queries get complex pretty soon. In such scenario, stored-procedures save a lot of time and are much easier to maintain and they work better with ADO.NET. In almost all scenarios, I would suggest using stored-procedures and ADO.NET. Move as much of the business rules and logic to stored procedures as you can...much easier to maintain this way.
Use Datasets (datatables) only to retrieve and read data. Any data that needs to be saved to database should be directly manipulated in the database ... no point doing it in dataset and then saving the same. In a multi-user environment it is almost always better to save the changes to database as soon as the user has clicked "save".
You may (should) use business objects within the application for business-logic processes.
Let us take a simple example of where you are saving a Contact (name, phone, email, address etc) and then retrieving a list of contacts added today...I would suggest you do it as follows:
1) Adding the contact - Client (web or otherwise) collects data --> data is saved in a Contact business object --> validate Contact object --> Call repository layer to save Contact object (adding a repository layer is useful but not-necessary to keep the data layer abstract from the client) --> Repository calls the data layer to save the contact object (here a simple ADO.NET call, using Command object, can be made to call the stored procedure to save the contact in database). No dataset was used in this use case.
2) Retrieving list of contacts -- Client calls the repository layer to get the list of contacts --> repository layer call the data layer to retrieve the data --> here the list of data is retrieved as a dataset(datatable) --> return the datatable back to the client and let the client read the data directly from datatable while rendering the data. Even a single contact can be retrieved as a dataset.
P.S: ORM is almost always an overkill. It is almost always used because certain developers like to keep everything object-oriented...so an extra layer gets added even though it does nothing useful (IMHO).
But, what if you have business logic (stored procedures) which can be used in many different applications.
So depends: if you make your application for different users with different backend storage, or you make many applications for users which doesn't change backend storage so often.
It is very important to have database integrity and rules independent from application (inner or outsource)
Almost all of the applications I write at work get their data from a central MSSQL database. This database has about 70 tables, and on average I'd say 25 or so columns per table. The database has developed over 5-10 years (I'm not entirely sure) and is full of idiosyncrasies and quirks. Foreign keys are irregularly implemented when it comes to naming and so on, as well as case and language mixing in table and column names.
I am not able to restructure the database itself as it would break a ton of backwards compatibility for applications needed in the daily work of most people in the office.
I've almost exclusively been using LINQ2SQL for interacting with the database and it works fine, but always requires a lot of manual joining of tables, either in some db repository or 'inline' when coding. So I've finally decided that I have to do something to once and for all ease the pain of working with this leviathan. This would preferably include implementing a clear naming scheme, joining relevant tables with foreign keys properly once and for all etc.
The three routes I can see are:
Creating a number of views, stored procedures and functions in the SQL to ease up my interaction with the DB. This obviously has the bonus of being usable in many languages, as opposed to a solution implemented in e.g. C#. The biggest drawback I can see here is that it would probably take a lot of time to do this properly, as well as being a bit harder to service a year down the road when I haven't looked at the SQL queries for a while. I would also need to implement another DB abstraction step inside my applications as I wouldn't want to work with just straight up DB calls (abstraction upon abstraction seems bad in this case, but maybe I'm wrong?)
Continuing on my LINQ2SQL road, but creating a once-and-for-all repository class that hides all the underlying tables in abstracted calls only. This idea seems more feasible in terms of development time, maintenance and single-point-abstraction.
Pulling off some EF4 reverse-engineering magic, using the designer to hook up relevant foreign keys and renaming table classes to fit my taste.
Any input on how this should/could be done, as well as any recommended reading you might have, would be most appreciated.
We have a very similar situation with our database. We went the EF route, but we used Code First. I know it sounds weird to use Code First when your database already exists, but due to the size of the tables and the number of tables, trying to do it all in the designer was not feasible.
You can use the "Reverse Engineer Code First" option in Entity Framework Power Tools to generate everything you need from your database.
I think that well thought out abstraction layer is better suits the needs of application if it is not based on physical schema of DB. I mean - the main goal of DAL is to hide tables from users leaving to them only valid "activities" thru stored procedures. In most cases this will outperform the direct data access and gives to you one more degree of freedom - to play with TSQL code and to implement additional logic/schema changes without needing to change the application.
We are using .net C# 4.0, VS 2010, EF 4.1 and legacy code in this project we are working on.
I'm working on a win form project where I have made a decision to start using entity framework 4.1 for accessing an ms sql db. The code base is quite old and we have an existing data layer that uses data adapters. These data adapters are used all over the place (in web apps and win form apps) My plan is to replace the old db access code with EF over time and get rid for the tight coupling between UI layers and data layer.
So my idea is to more or less combine EF with the legacy data access layer and slowly replace the legacy data layer with a more modern take on things using EF. So for now we need to use both EF and the legacy db access code.
What I have done so far is to add a project containing the edmx file and context. The edmx is generated using database first approach. I have also added another project that contains the POCO classes (by using ADO.NET POCO Entity Generator). I have more or less followed Julia Lerman's approach in her book "Programming Entity Framework" on how to split the model and the generated POCO classes. The database model has been set for years and it's not an option the change the table and the relationships, triggers, stored procedures, etc, so I'm basically stuck with the db model as it is.
I have read about the repository pattern and unit of work and I kind of like the patterns, but I struggle to implement them when I have both EF and the legacy db access code to deal with. Specially when I don't have the time to replace all of the legacy db access code with a pure EF implementation. In an perfect world I would start all over again with a fresh take one the data model, but that is not an option here.
Is the repository and unit of work patterns the way to go here? In order to use the POCO classes in my business layer, I sometimes need to use both EF and the legacy db code to populate my POCO classes. In another words, I can sometimes use EF to retrieve a part of the data I need and the use the old db access layer to retrieve the rest of the data and then map the data to my POCO classes. When I want to update some data I need to pick data from the POCO classes and use the legacy data access code to store the data in the database. So I need to map the data retrieved from the legacy data access layer to my POCO classes when I want to display the data in the UI and vice versa when I want to save data to the data base.
To complicate things we store some data in tables that we don't know the name of before runtime (Please don't ask me why:-) ). So in the old db access layer, we had to create sql statements on the fly where we inserted the table and column names based on information from other tables.
I also find that the relationships between the POCO classes are somewhat too data base centric. In another words, I feel that I need to have a more simplified domain model to work with. Perhaps I should create a domain model that fits the bill and then use the POCO classes as "DAO's" to populate the domain model classes?
How would you implement this using the Repository pattern and Unit of Work pattern? (if that is the way to go)
Alarm bells are ringing for me! We tried to do something similar a while ago (only with nHibernate not EF4). We had several problems running ADO.NET along side an ORM - database concurrency being a big one.
The database model has been set for
years and it's not an option the
change the table and the
relationships, triggers, stored
procedures, etc, so I'm basically
stuck with the db model as it is.
Yep. Same thing! The problem was that our stored procs contained a lot of business logic and weren't simple CRUD procs so keeping the ORM updated with the various updates performed by a stored procedure was not easy at all - Single Responsibility Principle - not a good one to break!
My plan is to replace the old db
access code with EF over time and get
rid for the tight coupling
between UI layers and data layer.
Maybe you could decouple without the need for an ORM - how about putting a service/facade layer infront of your UI layer to coordinate all interactions with the underlying domain and hide it from the UI.
If your database is 'king' and your app is highly data driven I think you will always be fighting an uphill battle implementing the patterns you mention.
Embrace ado.net for this project - use EF4 and DDD patterns on your next green field proj :)
EDMX + POCO class generator results in EFv4 code, not EFv4.1 code but you don't have to bother with these details. EFv4.1 offers just different API which does exactly the same (and it is only wrapper around EFv4 API).
Depending on the way how you use datasets you can reach some very hard problems. Datasets are representation of the change set pattern. They know what changes were done to data and they are able to store just these changes. EF entities know this only if they are attached to the context which loaded them from the database. Once you work with detached entities you must make a big effort to tell EF what has changed - especially when modifying relations (detached entities are common scenario in web applications and web services). For those purposes EF offers another template called Self-tracking entities but they have another problems and limitations (for example missing lazy loading, you cannot apply changes when entity with the same key is attached to the context, etc.).
EF also doesn't support several features used in datasets - for example unique keys and batch updates. It's fun that newer MS APIs usually solve some pains of previous APIs but in the same time provide much less features then previous APIs which introduces new pains.
Another problem can be with performance - EF is slower then direct data access with datasets and have higher memory consumption (and yes there are some memory leaks reported).
You can forget about using EF for accessing tables which you don't know at design time. EF doesn't allow any dynamic behavior. Table names and the type of database server are fixed in mapping. Another problems can be with the way how you use triggers - ORM tools don't like triggers and EF has limited features when working with database computed values (possibility to fill value in the database or in the application is disjunctive).
The way of filling POCOs from EF + Datasets sounds like this will not be possible when using only EF. EF has some allowed mapping patterns but possibilities to map several tables to single POCO class are extremely limited and constrained (if you want to have these tables editable). If you mean just loading one entity from EF and another entity from data adapter and just make reference between them you should be OK - in this scenario repository sounds like reasonable pattern because the purpose of the repository is exactly this: load or persist data. Unit of work can be also usable because you will most probably want to reuse single database connection between EF and data adapters to avoid distributed transaction during saving changes. UoW will be the place responsible for handling this connection.
EF mapping is related to database design - you can introduce some object oriented modifications but still EF is closely dependent on the database. If you want to use some advanced domain model you will probably need separate domain classes filled from EF and datasets. Again it will be responsibility of repository to hide these details.
From how much we have implemented, I have learned following things.
POCO and Self Tracking objects are difficult to deal with, as if you do not have easy understanding of what goes inside, there will be number of unexpected behavior which may have worked well in your previous project.
Changing pattern is not easy, so far we have been managing simple CRUD without unit of work and identity map pattern. Now lot of legacy code that we wrote in past does not consider these new patterns and the logic will not work correctly.
In our previous code, we were simply using transactions and single insert/update/delete statement that was directly sent to database assuming transactions on server side will take care of all operations.
In such conditions, we were directly dealing with IDs all the time, newly generated IDs were immediately available after single insert statement, however this is not case with EF.
In EF, we are not dealing with IDs, we are dealing with navigation properties, which is a huge change from earlier ADO.NET programming methods.
From our experience we found that only replacing EF with earlier data access code will result in chaos. But EF + RIA Services offer you a completely new solution where you will probably get everything you need and your UI will very easily bind to it. So if you are thinking about complete rewriting using UI + RIA Services + EF, then it is worth, because lot of dependency in query management reduces automatically. You will be focusing only on business logic, but this is a big decision and the amount of man hours required in complete rewriting or just replacing EF is almost same.
So we went UI + RIA Services + EF way, and we started replacing one one module. Mostly EF will easily co-exist with your existing infrastructure so there is no harm.