On many sites/blogs I noticed that people, who want to explain linq mechanism, write Linq Queries and provide SQL translation for that. How can I get the translation for my own queries?
I'm working with EF .Net 4.0 in VS2010. Is there a place (property or even some third-party tool) where I can see what they're being translated into?
You can use the ObjectQuery.ToTraceString method:
var query = ...
string sql = ((System.Data.Objects.ObjectQuery)query).ToTraceString();
However, some shortcomings of this approach is that it will only show queries, not updates/inserts/deletes. Also, it won't reveal the parameters used.
If you need as much detail as possible from the query then use the SQL Server Profiler as Neil suggested.
Julie Lerman has a good article with different options on MSDN: Profiling Database Activity in the Entity Framework. She mentions:
ObjectQuery.ToTraceString method
Visual Studio 2010 Ultimate's IntelliTrace
EFTracingProvider
The simplest method is to use SQL Profiler. I have found this a real god-send when it comes to debugging.
You can use LinqPad, you can query your entity model and view the generated SQL.
Related
is it necessary to use LINQ for sql purposes in MVC ? can't we use traditional queries like:
Select name from tbl where id = 2;
instead of LINQ ? and why linq in any case ?
ASP.NET MVC in no way restricts your choice of data access technology. In fact, model binding works with objects, and MVC has no idea whether your objects represent some database or not.
Besides, if you were to use LINQ at all, you would do best to use Entity Framework (a.k.a. LINQ to Entities) and not LINQ to SQL, which is much more limited.
Linq to SQL, EntityFramework, nHibernate - are ORM (Object-relational mapping) tools. ORM represent database objects as standard .NET classes.
Raw SQL can be used, when you are inserting a lot of data, and you need a good performance. In all other cases you should to use ORM.
And if you decide to use ORM, I advise you to use EntityFramework; it's more powerful than LINQ to SQL.
You don't need to use linq at all. I usually use dapper.net for my data layer, mapping SQL queries to objects. It's personal preference.
You are not obliged to use Entities Framework, as you are not obliged to use anything in particular.
Microsoft strongly suggests using the Entities Framework because it is an ORM integrating very easily with the whole Microsoft ecosystem, using the LINQ query language which is integrated in the .NET languages specification. This integration happens through the Linq to Entities query language and the respective tools provided in Visual Studio.
As you will see, Entities Framework (as every other ORM) has the overhead of the learning but in my opinion, it totally pays you back as using an ORM leads to faster development and more maintainable source code. I would strongly suggest using an ORM (it has many advantages) and I suppose since you are already familiar with Microsoft ecosystem, Entities Framework would be the best choice.
Hope I helped!
Well, if you want to use this style of queries you can use stored procedures this is to close to the normal query, just and a Linq-to-SQL file into your project and drag and drop you stored procedures then you can use them like methods and this is a link http://msdn.microsoft.com/en-us/library/bb386946.aspx
Note that Linq-to-SQL is integrated only with SQL Server
No, you do not have to use LINQ at all, or any other ORM frameworks, you an work directly against a database.
In .Net this is typically done using ADO.Net, for example using the System.Data.SQL namespace.
See code examples and official documentation here
How can I use sql query, in sql language, if I used entity framework to make the connection?
I understood from this post that ObjectContext.ExecuteStoreQuery won't help because it works only with some queries (not 1:1 to sql language).
The other option mentioned there is to use ObjectContext.Connection and write "classic" ADO.NET code from there, but I just can't figure out how.
Can someone please write a very simple code example how can I perform a simple query like
select MAX(customer_id) from Customers
with the entity framework? I know that Linq-To-Sql exist, but I prefer to use sql language, it looks simpler to me and I am more familiar with it.
use the Database.SqlQuery method to execute SQL queries
var maxId= context.Database.
SqlQuery<int>("select MAX(customer_id) from Customers")
.SingleOrDefault();
This should work assuming context in your DataContext class object.
Not an answer, but I have to...
I prefer to use sql language
Do yourself a favour and "forget" SQL! Linq is really not that hard. SQL in string literals is maintenance hell. Linq is strong-typed so the compiler guards you against code corruption. You've got intellisense, far less ceremonial code, it is much easier to express complex queries. And so forth and so on.
Your statement is a piece of cake in Linq.
context.Customers.Max(c => c.customer_id)
Well, just an advice :D
I am using L2S in my application but i'm switching more and more to dapper.net because i'm having major issues with query performance and the annoying n+1 selects problem.
Its working fine, but i miss the comfortable LINQish style of writing predicates when filtering data.
So my question is, how can i translate a predicate in form of Func<T, bool> to a SQL Server where clause to use it with dapper?
I think someone must have done this before, or are all the dapper users handcoding their sql statements?
As the title suggests, maybe it is an option to call the LINQ2SQL provider for SQL Server?
Basically i'm looking for something like the inverse of dynamic linq.
There are ways to see the SQL generated by LINQ. See the article Seeing the SQL Generated by LINQ to Entity Queries from Visual Studio Magazine.
Now that I understand better what you're after, I did a little more looking into this and found a couple of related posts that are worth a look:
Dynamic where clause in dapper which suggests using a Stringbuilder, but one of the comments points to a Sam Saffron article, Porting LINQ-2-SQL to Dapper for great justice, that talks about a contributed SqlBuilder that might help you.
Generate a SQL clause using a Linq-to-Sql Expression which suggests using a LINQ Where call and grabbing the WHERE clause from the generated SQL.
Can anyone point out some good LINQ training resources. Mostly interested in getting some developers that are very skilled with SQL up to speed using Lambda and LINQ queries. They are struggling with some of their more advanced queries and fall back on ExecuteQuery() to kind of do the LINQ thing. Queries that used to be easy in TSQL but are now very difficult for them with LINQ.
I can't recommend LinqPad more highly. It's a free Windows app that allows you to use Linq interactively against your data source. It includes tutorials, and allows you to query your data source interactively like you would do in a query analyzer. An excellent resource when trying to make the jump form SQL to Linq.
http://www.linqpad.net/
Pro LINQ should have most of the information they need in chapters 12-15.
I would suggest you look at a utility named Linqer (http://www.sqltolinq.com/). It converts T-SQL to Linq queries. I have found it quite useful at times (I have no relationship with the product).
Also, get LinqPad. This is a must. http://www.linqpad.net/
Randy
I find I can do more with NHibernate, and even Castle than with the Linq to Entities, or linq to SQL.
Am I crazy?
No you're not crazy. nHibernate is a full OR Mapper, Linq to SQL and Linq to Entities don't implement everything you'd expect from an OR mapper and targeted at a slightly different group of developers.
But don't let that put you off linq though. Linq is still a pretty good idea.. Try Linq to nHibernate :-)
The big drawbacks to NHibernate, Castle, etc., is that they're not exactly light-weight (especially NHibernate.)
Linq to SQL is good for a light-weight, limited use ORM.
I've used both NHibernate and LINQ to SQL. From my point of view it depends on the project, if I need something quick, I would choose L2S, it's so simple to create the dbml mapping and start using it. If I'm developing a more highlevel enterprise solution I would go for the tried and trusted ORM - NHibernate, I find the logging & transaction features simple to use.
LINQ to SQL has a relatively short learning curve, NHibernate has a much steeper learning curve.
LINQ to SQL only supports SQL Server, so if you've an Oracle database then the decision is already made - NHibernate.
I'd recommend checking out http://www.summerofnhibernate.com/ for excellent screencasts on learning NHibernate.
One thing to bear in mind is that NHibernate can be an absolute pig to configure - especially since its based mainly on XML config files because of its roots as the original Hibernate.
Fluent NHibernate goes some way to making this less painful.
Linq certainly though fits in with the general 'way' in which .NET works.
Blockquote Linq certainly though fits in with the general 'way' in which .NET works
Yikes, this kind of sentiment scares me. The RAD stuff built into .net is NOT how dot net works, it's just a tool set for getting prototypes up. .NET allows us to do full DDD applications, w/ high levels of cohesion, seperations of concerns, and allows us to write decoupled code, despite all the attemps ms makes to couple things. I would strongly disagree that .net likes to be coupled, certian tools like to be coupled, i'll include linq to sql in this fray. linq to sql destroys the idea of having a seperate domain model. I cringe at the thought of using my database schema as the underlying model objects. Proper ORM tools should allow us to model our domain first, then link our relational database to these models. NOT the other way around.
I have not tried the Entity Framework, but I definitely would recommend NHibernate over Linq to SQL; The biggest reason I can give is just the control. Linq to SQL likes to have a lot more control over everything, loading the object and maintaining all kinds of tracking information about the object. If you serialize/deserialize, the tracking information can be lost and strange things can happen when saving it again. NHibernate works more as a repository should - You hand it whatever object you want (that you have configured it to understand, of course), and it puts it away in the database, regardless of what you've done with it.