I am encountering some performance problems with my Entity Framework Code-First queries and I believe that precompilation may be the answer. If I were using "normal" Entity Framework, I would simply use the CompiledQuery.Compile method to precomiple my queries. But since I have a DbContext and not an ObjectContext, I can't get this to work.
I do realize that DbContext is an IObjectContextAdapter, which gives me access to the ObjectContext, but I cannot find the method that lets me get an IQueryable from my object context that works in my precompiled query. I tried to use CreateObjectSet, but when EF tried to run the query it complained that it couldn't convert that method into SQL.
So what is the best way to precompile LINQ queries against a Code-First DbContext?
This will be probably solved in EFv4.2 EF vNext (currently in the very first CTP) by auto-compiled LINQ queries.
As from the official announecment:
"No compiled query support from DbContext
Unfortunately due to some technical limitations in the compiled query functionality we shipped in .NET Framework 4.0 we are unable to support compiled queries via the DbContext API. We realize this is a painful limitation and will work to enable this for the next release. "
Link.
Related
I'm actually working on a project who use a very big linq to entity query (around 250 lines) who works with a lot of different entities.
This query depend of few parameters (3 or 4 max) so I think to "store" the expression tree of my query and modifying this one with just my few parameters like this.
IQueryable<Foo> myQuery =
GetBaseQuery()
.Where(a => a.Param1 == "foo")
.Where(a => a.Param2 == "bar");
Apart using compiled queries, is there a way to do that ?
This problem has some conditions
I use DbContext and changing to ObjectContext is difficialy possible and it seems that this is a pre requities for using compiled queries.
I use Visual Studio 2010 so... i'm limited to .NET 4 and entity framework 4.3 (no .NET 4.5, EF5 and autocompiled queries unhopefully)
So, Is there a way to
Store an expression tree who will be just used as a "base" and will not take too much time to be generated ?
Or using .NET 4.5 in visual studio 2010 ?
Or using Compiled queries with a DbContext
REALLY Thank's by advance !!!
Reading between the lines, it seems you want compiled queries with DbContext. (This isn't really the same as storing the LINQ expression tree, but that doesn't seem to be the performance bottleneck in the testing we have done anyway.) As far as I know the options you have are:
Use EF5 with .NET 4.5. Even if you are using VS2010 and targeting .NET 4 if you install .NET 4.5 on the machine where the app is run then you will get auto-compiled queries.
Use EF6 with .NET 4 or .NET 4.5. EF6 moves the auto-compiled query code out of the .NET Framework so it gets used even when running on .NET 4.
Use ObjectContext and CompiledQuery
I'm not aware of any way to use CompiledQuery with DbContext and there also aren't any plans to make this work.
Does anyone know why LinqPad cannot autogenerate an Entity Framework context object (like it does with Linq-to-SQL)? It seems I have to create an assembly containing an EF context and then reference the assembly in LinqPad. But I don't need to do this with L2S.
Thanks very much.
LINQPad uses LINQ-to-SQL for automatic data contexts because it's lighter and faster. LINQ-to-SQL also generates better SQL in many cases and allows arbitrary functions in the final projection.
It wouldn't be hard, in principle, to write a driver for Entity Framework. The reason it isn't present as an option is lack of demand.
If you wanted, you could implement EF support seamlessly as a third-party driver. The only tricky thing to implement is supporting every version of EF.
Hey I have a unique and troubling situation.
I am working on a project where my team has used a mixture of Enterprise Data Library plus Entity Framework. Obviously this probably not recommended but it is what I'm stuck with. I would like to take a method written using Enterprise Data Library and also take a different method written using Entity Framework, and wrap both of these methods in a single transaction (without requiring Microsoft Distributed Transaction Service). I'm hoping to minimize rewriting code and be able to wrap the two methods in a single transaction just as they are. Is this possible? Thanks.
Using SQL Server 2008 and .NET 4.0
I suppose you want to mix EF and EntLib queries in the same TransactionScope, without using DTC.
Good news: it's possible. If you use exactly the same connection string for EntLib DAAB and EF DbContext, it will work, depending on the versions of EF, EntLib and SQL Server.
So what you have to do is:
check you have the right versions
get the version of your connection string changed by EF and use it instead of yours.
For 1, I have checked these combinations:
SQL Server must be 2008 or older
EntLib 4.1 + EF 5 doesn't work
EntLib 5 + EF 5 works
For 2, to get the connection string changed by EF you have to debug the execution of code that uses an instance of a DbContext. Set a breakpoint and watch or inspect the DbContext Database.Connection.ConnectionString property. That's the EF version of your connection string. Use it for both EF and EntLib and you'll get rid of DTC.
EF and ORM.
I recently realized that is possible using POCO to have clean classes not plumbed with EF auto generated code.
I saw the new release of EF 4.1 and the use of Code First approach and DbContext.
My questions:
What is the difference between Code First approach and Poco approach?
Can we use Code First (DbContext and DbSet) instead of POCO + Repository pattern?
Thanks for your time on this.
They're completely different things, and you can use them together.
POCO means that your entity classes are "normal" classes, not dependent on any specific ORM layer.
A DbContext is an object that enables you to access the database in an object-oriented way (like ObjectContext in earlier versions of EF).
Have a look at this tutorial for examples.
We are about to start using EF as our ORM. We have our own MetaData representing the databse stracture and we will generate whatever we need off of that.
We are wondering whether to use the "old" EDMX approace, or to use the new EDMX free approach (wiht DbSet and DbContext). As we do our own code/edmx generation it seems odd to generate an EDMX and then generate objects and context off of it.
The thing is I don't see much talk about about the EDMX free approach. Is it being used by anyone? Can someone with experience share their impressions? Are there known limitations? Are there pros and cons?
Asher
Are you asking if anybody is using code-first? :) By checking the number of questions in entity-framework-4.1 and code-first and ef-code-first I guess people are using it a lot. There were several questions about code-first x non code-first. Some of I answered:
EF POCO code only VS EF POCO with Entity Data Model
EF Model First or Code First Approach?
EF 4.1 Code-first vs Model/Database-first
Generally there are four approaches:
Model first (database generated from EDMX)
Database first (EDMX generated from database)
Code first (database generated from code mapping)
Database first with code mapping (code mapping manually created for existing database or manually updated mapping generated by EF Power Tools CTP)
Selection of the approach usually depends on the way how you want to develop application (as described in linked answers). It also depends if you want to use ObjectContext API or DbContext API. The former one is usually used with first two approaches (but the secret is it should work with code-first as well) the later one with all of them.
Code first has some limitations - it doesn't support all mapping features EDMX does for example:
Stored procedures mapping (it doesn't mean you cannot execute SP when using code first)
SQL functions mapping
Advanced EDMX features like defining queries, query views, model defined functions
etc.
What I don't understand is why are you trying to combine your code generation tool with EF. Either use your stuff or use EF's stuff. You will avoid complications and incompatibilities.