i am new in MVC and entity frame work and i want to create Code first entity frame work.
we have already created project in asp.net and we want to migrate in mvc. we have lots of stored procedure and some procedure return complex data combination of 10 to 12 tables...
As a Proof of Concept we wan't to develop 3 to 4 pages...
i have some question regarding new start.
1) Should i used entity frame work if yes then which is better entity frame work model
Database first
Model first
code first
2) how to integrate stored procedure in Code first model
3) in each page we have minimum 7 to 8 table result there... how i will handle in entity frame work.
this is my first project in mvc and entity framework please help me with appropriated answer.
first, this has nothing to do with MVC. this is purely a data access issue.
second, this is sort of missing the point of using entity framework. if the goal is to migrate away from stored procs that one thing, but to use EF and continue to execute the stored procs defeats the purpose of using a ORM like EF.
Instead for your procs I would stick with raw ADO.Net, or use Dapper.Net to convert the stored proc result sets into objects.
EF would be a better choice as your convert each proc into EF linq queries. It's not that you can't execute procs (or raw sql) from EF, but it doesn't make much sense. Especially with how you describe the procs.
Related
I am building an application that will interface with my database backend using EF 6. I have my database built so I will be going the database first approach.
One of the goals will be to utilize the grid control from DevExpress and allow the user to view a Master/Detail style of information for each Facility in my Facility table.
I need the ability to update/insert so I would assume using a view would not be as good as actually supplying the context to the grid's data source.
My question is trying to understand the overhead involved with Entity Framework. If my table contains 20 columns but my Grid only needs 10 of these for viewing/updating/inserting does the application still load ALL of the information into memory? Am I better off using a view for the grid and some form of custom routines for an update?
It doesn't necessarily load all of the columns. If you're smart about it, you can only have it load those columns that you need using LINQ to Entities.
For example:
var records = db.MyTable.Where(...Some condition...).ToList(); will return all the columns.
But doing it this way
`var records = db.MyTable.Where(...Some condition...).Select(x => new MyModel { ...some fields here... }
will only load those fields that are specified.
I've worked with DevExpress and Entity Framework combined before, and I can tell you that it's relatively painless as long as you understand what you're doing with Entity Framework, and don't just blindly have your grids make queries that can get expensive.
I'm using Entity Framework 5, and I reverse engineer code first the database I'm using, and then I added an ADO.NET Entity Data Model so that I can use Stored Procedures as reverse engineer code first didn't provide the use of sprocs. Is this the only way to access sprocs?
Also, I realize that after the reverse engineer code first process is done a bunch of classes (tables from the database) are created but as soon as I add the ADO.NET Entity Data Model, most of the classes go away. Does anybody know why?
DbContext.Database property exposes useful methods
http://msdn.microsoft.com/en-us/library/system.data.entity.database(v=vs.103).aspx
ExecuteSqlCommand( string, object[] )
http://msdn.microsoft.com/en-us/library/system.data.entity.database.executesqlcommand(v=vs.103).aspx
SqlQuery<TEntity>( string, object[] )
http://msdn.microsoft.com/en-us/library/gg696545(v=vs.103).aspx
There is a pattern that you can follow to create or support store procedures with the code first approach. here is a link that you can use to follow this:
http://www.codeproject.com/Articles/179481/Code-First-Stored-Procedures
In few words you need to do the same that you do with model first, create a class that supports the inputs and a class that supports the result set.
And about the Data Entity Model and missing classes. You need to consider that you only can have one approach in a project: code first/(model first/database first), so this could be the reason why you are not seeing those clases.
You can use Context.Database.SqlQuery to run SP.
I would like to use Entity Framework 5 from which I can use one MVC Model that can span two or more databases.
Is this possible?
In other words, have one EF model that can use two or more databases. Because with MVC, you can only use 1 model in a View. Some of the data with some of the Views can come from different databases. In order to use the model binder in MVC and map it to EF 5 columns, I would need to accomplish this.
ASP.NET MVC is NOT dependent on Entity Framework.
ASP.NET MVC is a framework for building web application that stick with the Model View Controller pattern. It is not bounded to Entity framework. It can work with any data access technologies like LINQ2SQL / Entity Framework / Pure ADO.NET etc.. that means you can develop MVC application with or without using Entity Framework.
I assume you want to get data from 2 different databases and load a model object. You can do that by writing a select query which gets data from 2 databases and put that in a Stored procedure and put that proc in your database which your DbContext is communicating with. Then execute the stored proc and load the Model object.
a sample procedure which gets data from 2 databases
CREATE PROCEDURE GetCustomer(#id int)
AS
BEGIN
SELECT C.ID,A.DateReceived
FROM FirstServerName.DbName.dbo.Customer C
INNER JOIN SecondServerName.DbName.dbo.Applications A
ON A.CustomerID=C.CustomerID
AND A.CustomerID=#id
END
To execute the stored proc with Entity framework, you can use Database.SqlQuery method
var idParam = new SqlParameter { ParameterName = "#Id", Value = 414};
var result = context.Database.SqlQuery<Customer>
("exec GetCustomer #Id", idParam).ToList();
This will execute your proc and load the data to an instance of Customer class, assuming the result set structure and your model class structure look similar.
You may need to adjust the permissions of the stored proc to read data from the relevant databases /tables.
What Shyju is saying is that MVC doesn't care or know anything about your Entity Framework data model or database. As such, the idea that an MVC model can span two databases is like saying an airplane can span two hammers.
As above the M in MVC is whatever you want it to be. Microsoft don't specify what Model actually is. It certainly doesn't have to be an EF Model (although some code samples from MS use that as an example)
I'd suggest that M should be a ViewModel and should be unrelated to your data layer. Then use a tool like Automapper to map from a domain model to a ViewModel. The ViewModel encapsulates the data you want to show and any specific web view specific information that you want to display. Then when you post back the ViewModel you can use that to update the domain models appropriate fields etc and persist that to both databases. This is a good article on the subject of ViewModels http://lostechies.com/jimmybogard/2009/06/30/how-we-do-mvc-view-models/
I am using Database first modal and EF4.0.
I have created a stored procedure which required two input parameters and return dynamically column in result-set i.e. columns are not fixed in result.It may be 5 or 7 or 10 and so on.
I am using Grid-view and passing the result-set in it's data-source.
How can i call stored procedure in this case.
thanks.
You must use ADO.NET and data reader / data adapter directly. EF can work only with stored procedures producing strongly typed results known at design time (you must create class for them).
is there an possibility to call the Math.Sin()-function in a Linq To Entites (Entity Framework 4) -Query?
I've read, that the current Entity Framework 4 doesn't implement this function.
Maybe there's a workaround to this solve problem?
(I don't want to invite all entries in the memory.)
Thanks and best regards
Several functions that (usually) have obvious SQL counterparts, like Math.Sin can't be used directly in Entity Framework queries. Presumably this is because they can't be reliably translated to different SQL implementations. A ton of MSSQL-specific functions are, however, exposed as static methods in the class System.Data.Objects.SqlClient.SqlFunctions. They throw exceptions if you call them directly, but are translated into the proper SQL if used in a LINQ query.
See this blog post about the magic that's happening under the covers (namely the EdmFunction attribute).
It is certainly possible to use such function starting with EF4. In EF4, EF team introduced SqlServer functions that can be consumed in linq. You should alway consider using canonical functions cuz they are database agnostic and every vendor should convert those functions to store specific equivalent. However when such functions are not available, you can resort to SqlServer namespace (ESQL) or SqlFunctions for linq
from l in db.Locations
select SqlServer.Sin(l.Latitude) + SqlServer.power(l.Longitutde)
I cover several of these options in my functions chapter in my book. Specifically you can look at 11-10 recipe Calling database function in esql
11-11 Calling Database Function in LINQ
Unfortunately it's impossible to call Math.Sin in a LinqToEntities query (or Entity SQL query).
The only way to accomplish this without resorting to retrieving all objects first, is to write a SQL query that does what you want and call it via ObjectContext.ExecuteStoreQuery. This isn't as bad as it sounds because you can still get back typed results.
EDIT: After reading the other answers, it appears that it is possible to call these types of functions (SqlFunctions contains 44 functions with various overloads). I leave my original answer as is because it's another way of achieving the same result.