We Keep Coding

ORM Code First versa Database First in Production

I have been using SQL since 1985, so am very comfortable with DB servers.
I see (C#) Code First as yet another fad, that comes and goes. It seems to suit people that have no DBA background. Equally if using Code First and you have not idea what DB you are connecting to eg it might be Mongo later that too is a useful abstraction. Code First does not let itself to Database Diagrams so you can see what is going on.
I would like to know how you promote changes into a production SQL server using code first, where you have no desire to Drop and recreate the DB, unlike using an ALTER TABLE command. I have used tools from Red-Gate that make DB code promotions easy.
So why Code First?
How do you move DB Changes into production?

The code first approach is something that is really nice to have when you're prototyping applications and "don't care" about the "persistence layer" too much in the beginning. It helps getting quick results in a time when things are not at all well defined yet, because you can always very easily drop and re-create your database of your greenfield project.
Unfortunately, most tools that offer this approach do not really help transitioning from the "greenfield project mode" to the more longterm "legacy project mode" where database migrations are essential. In fact, not only are database migrations difficult to achieve in "client model first" approaches, but more importantly, the likelihood of the database model not being well designed is quite high.
Developers pay a high price for the quick win - as always. It is really not a good idea and a lot of more experienced developers who are used to working with legacy, do agree with you: Go database first, and derive your client (e.g. ORM) models from it.
I have written about this topic here, including the advantage of using client model source code generation.

Entity Framework VS pure Ado.Net

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?

Entity Framework approach for production

We are building this .NET application using Entity Framework as our DB connector. I know all about the stuff of picking the right approach based on your circumstances like "do you have an existing database?", "do you prefer modelling instead of coding". But after some reading I've found that it's not the only thing to think of as the upgrade process of the database when it's already in production is really important, espacially for us.
So which approach is best for production use with Entity Framework. For the moment we have an existing database. I prefer to use the model and update the database from it but then we have lack of functionality in default values of columns and the model can be hard to work with in teams so what we need is basically some best practice here.
For production use: Database First, Model First or Code First?

Someone else might chime in here and tell you to use model migrations with the code first approach. That may be a solution, it's just not my preference.
We manage an in-motion database using EF code first, however I would not be able to do it without one hugely beneficial Visual Studio feature: SQL Schema Compare. I believe this feature is only available in the Premium and Ultimate versions of the product.
Each time our model changes, I put 2 copies of the database schema on my local machine: the new version, and the current production version. If you run Schema Compare using the new version as the source and the production version as the target, it will generate a SQL script that you can run against your production db to bring its schema and data in line with the changes.
The SQL it generates often needs some editing before it can be run in production, but it will do a lot of the hard work for you -- disabling constraints, add / drop indexes, and moving data from an old table into a new version of it. It will also warn you of potential issues when changing the schema.

C# Entity Framework - Handling destructive autogen DB scripts with model first design

I recently started a new personal project to learn Entity Framework. My end goal is to make a desktop game that uses SQL compact for data management and uses Entity Framework for the game objects. Not actually knowing there were multiple ways to start EF (model first, code first, db first) I went with the most obvious choice of model first.
I've been working with it successfully now, however one thing concerns me, especially post-development. My goal with the game is that users can update to the latest version without losing any of their existing data. The current issue is that all the generation scripts are destructive by nature (dropping everything then recreating it) - that means I can't run those against the user SQLCE DBs out in "production", so I need to come up with an alternative plan of action.
That said, does anyone have recommended solutions on best practices? In previous desktop apps, I've traditionally used XML/binary to store data, which allows me to easily update the "schema" without affecting existing data (versioning in the app tailors the Load() according to the version, while the Save() always saves in the latest version).
What are some recommendations on handling this problem using SQLCE?

What you need, if understood right, is to utilize migrations which come with EF. Since the question is general this link should best guide you to what you need I think...
http://blogs.msdn.com/b/adonet/archive/2012/02/09/ef-4-3-code-based-migrations-walkthrough.aspx
With migrations which you can tailor manually if needed (and come in the shape of code which is applied at each point of change, incrementally) and you can also supply your 'seeding' if required.
i.e. you should be able to do most of what you require, delete, remove old incompatible data - and seed the new one that you have - and all related to a particular migration step you have.
How would that work with your app deployment specifically, that's a bit more complex I guess, but this should get you started, and then with each db version-breaking change your new code update would contain all the migrations since the previous update (or just one usually is enough, i.e. make it be one with each update) and the code to tear-down or create new things.
hope this helps,

Which is the "best" data access framework/approach for C# and .NET?

(EDIT: I made it a community wiki as it is more suited to a collaborative format.)
There are a plethora of ways to access SQL Server and other databases from .NET. All have their pros and cons and it will never be a simple question of which is "best" - the answer will always be "it depends".
However, I am looking for a comparison at a high level of the different approaches and frameworks in the context of different levels of systems. For example, I would imagine that for a quick-and-dirty Web 2.0 application the answer would be very different from an in-house Enterprise-level CRUD application.
I am aware that there are numerous questions on Stack Overflow dealing with subsets of this question, but I think it would be useful to try to build a summary comparison. I will endeavour to update the question with corrections and clarifications as we go.
So far, this is my understanding at a high level - but I am sure it is wrong...
I am primarily focusing on the Microsoft approaches to keep this focused.
ADO.NET Entity Framework
Database agnostic
Good because it allows swapping backends in and out
Bad because it can hit performance and database vendors are not too happy about it
Seems to be MS's preferred route for the future
Complicated to learn (though, see 267357)
It is accessed through LINQ to Entities so provides ORM, thus allowing abstraction in your code
LINQ to SQL
Uncertain future (see Is LINQ to SQL truly dead?)
Easy to learn (?)
Only works with MS SQL Server
See also Pros and cons of LINQ
"Standard" ADO.NET
No ORM
No abstraction so you are back to "roll your own" and play with dynamically generated SQL
Direct access, allows potentially better performance
This ties in to the age-old debate of whether to focus on objects or relational data, to which the answer of course is "it depends on where the bulk of the work is" and since that is an unanswerable question hopefully we don't have to go in to that too much. IMHO, if your application is primarily manipulating large amounts of data, it does not make sense to abstract it too much into objects in the front-end code, you are better off using stored procedures and dynamic SQL to do as much of the work as possible on the back-end. Whereas, if you primarily have user interaction which causes database interaction at the level of tens or hundreds of rows then ORM makes complete sense. So, I guess my argument for good old-fashioned ADO.NET would be in the case where you manipulate and modify large datasets, in which case you will benefit from the direct access to the backend.
Another case, of course, is where you have to access a legacy database that is already guarded by stored procedures.
ASP.NET Data Source Controls
Are these something altogether different or just a layer over standard ADO.NET?
- Would you really use these if you had a DAL or if you implemented LINQ or Entities?
NHibernate
Seems to be a very powerful and powerful ORM?
Open source
Some other relevant links;
NHibernate or LINQ to SQL
Entity Framework vs LINQ to SQL

I think LINQ to SQL is good for projects targeted for SQL Server.
ADO.NET Entity Framework is better if we are targeting different databases. Currently I think a lot of providers are available for ADO.NET Entity Framework, Provider for PostgreSQL, MySQL, esql, Oracle and many other (check http://blogs.msdn.com/adonet/default.aspx).
I don't want to use standard ADO.NET anymore because it's a waste of time. I always go for ORM.

Having worked on 20+ different C#/ASP.NET projects I always end up using NHibernate. I often start with a completely different stack - ADO.NET, ActiveRecord, hand rolled wierdness. There are numerous reasons why NHibernate can work in a wide range of situations, but the absolutely stand out for me is the saving in time, especially when linked to code generation. You can change the datamodel, and the entities get rebuilt, but most/all the other code doesn't need to be changed.
MS does have a nasty habit of pushing technologies in this area that parallel existing open source, and then dropping them when they don't take off. Does anyone remember ObjectSpaces?

Added for new technologies:
With Microsoft Sql Server out for Linux in Beta right now, I think it's ok to not be database agnostic. The .Net Core Path and MS-SQL route allows you to run on Linux servers like Ubuntu entirely with no windows dependencies.
As such, imo, a very good flow is to not use a full ORM framework or data controls and leverage the power of SSDT Visual Studio Projects (Sql Server Data Tools) and a Micro ORM.
In Visual Studio you can create a Sql Server Project as a legit Visual Studio Project. Doing so allows you to create the entire database via table designers or raw query editing right inside visual studio.
Secondly, you get SSDT's Schema Compare tool which you can use to compare your database project to a live database in Microsoft Sql Server and update it. You can sync your Visual Studio Project with the server causing updates in your project to go out to the server. Or you can sync the server with your project causing your source code to update. Via this route you can easily pick up changes the DBA made in maintenance last night and push out your new development changes for a new feature easily with a simple tool.
Using that same tool you can compute the migration script without actually running it, if you need to pass that off to an operations department and submit a change order, it works for that flow to.
Now for writing code against you MS-SQL Database, I recommend PetaPoco.
Because PetaPoco works Perfectly inline with the above SSDT solution. PetaPoco comes with T4 text templates you can use to generate all your data entity classes, and it generates the bulk data layer classes for you.
The catch is, you have to write queries yourself, which isn't a bad thing.
So you end up with something like this:
var people = dbContext.Fetch<Person>("SELECT * FROM People where Username Like '%#0%'", "bob");
PetaPoco automatically handles parameterizing #0 for you, it also has the handy Sql class for building queries.
Furthermore, PetaPoco is an order of magnitude faster than EF6 and 8+ times faster than EF7.
So in total, this solution involves using SSDT for SCHEMA management, and PetaPoco for code integration at the gain of high maintainability, customization, and very good performance.
The only downfall to this approach, is that you're hard tieing yourself to Microsoft Sql Server. However, imo, Microsoft Sql Server is one of the best RDBM's out there.
It's got DBMail, Jobs, CLR object capabilities, and on and on. Plus the integration between Visual Studio and MS-SQL server is phenomenal and you don't get any of that if you choose a different RDBMS.

I must say that I never used NHibernate for the immense time that needed to start using... time wasted on the XML setup.
I recently did a web application in MVC2, where I did choose ADO Entities Framework and I use Linq all the time.
I must say, I was impressed with the speed! and our site was having around 35 000 unique visitors per day, in around 60Gb bandwidth per day (I reduced radically this 60Gb number by hosting all static files in Amazon S3 - Great .NET wrapper they have, I must say).
I will always go this way. It's easy to start (just add new data item, choose tables and that's it! for every change in the database we just need to refresh the model - made automatically in just 2 clicks) and it's fun to use - Linq rules!