I am an Entity Framework newbie and am wondering if I am able to use it in the way I would like to. I am using Visual Studio 2010 and .NET 4.
I have a Content Management system which stores all the data in an xml field of a table. The table - cmsContent - contains only two fields, id and XmlNode
I want to create stored procs that query the XML field to bring back meaningful data, Product data in this case. e.g...
SELECT
C.id AS [Id],
C.xmlNode.value('(/node/data[#alias = ''ProdName''])[1]', 'NVARCHAR(1024)') AS ProductName,
C.xmlNode.value('(/node/data[#alias = ''ProdDesc''])[1]', 'NVARCHAR(1024)') AS ProductDescription
FROM cmsContent C
WHERE
C.xNode.query('data(/node[1]/#nodeTypeAlias)').value('.', 'VARCHAR(30)') = 'Product'
I then want to map the output of these stored procs to my entity classes via a the EDMX enity diagram. So I would want to map the above query to a class called Products. The products class will be read only, there is no need to upate these object as this is doen via the CMS.
Would this be posssible to use the entiry framework in this way? If so how, as I can’t get the Stored Procs to generate the required classes in the EDMX diagram as this doesn't happen when i use the wizard?
If it's readonly, then you can provide a DefiningQuery for the EntitySet in the Storage Model. This essentially acts as a read-only view of the store and you can define the result shape however you want. You can then either map it to an entity or a complex type (tho a complex type may be easier if it's read-only.)
<Schema ...>
<EntityContainer ...>
<EntitySet Name="blah" EntityType="BlahModel.Store.blah">
<DefiningQuery>
select ... from blah
</DefiningQuery>
</EntitySet>
</EntityContainer>
...
</Schema>
I think you have to create a complex type, and map the SP to this. See this MSDN article.
Related
I am working with entity framework 6 with database 1st approach. I changed the datatype of my columns in the table and after updating my model I got the following error:
Error 1 Error 2019: Member Mapping specified is not valid. The type
'Edm.Int32[Nullable=False,DefaultValue=]' of member 'Warranty' in type
'pjModel.Bill' is not compatible with
'SqlServer.nvarchar[Nullable=False,DefaultValue=,MaxLength=50,Unicode=True,FixedLength=False]'
of member 'Warranty' in type 'pjModel.Store.Bills'.
what I understand that there is some compatibility issue between datatypes of framework and sql server.
Also when I opened the .edmx file with XML viewer, it clearly shows that changes are propagated in the model i.e data type has been updated, but in the diagram view when I right click the particular column it still shows the old datatype.
I can provide more information if required.
The issue has been resolved. I manually change the type from the diagram view and then it get mapped with the model class.
Same problem here, using EF6, after changing on a database table a field from int to bit.
It was not enought to delete property from model designer, and create it again, as the table mapping refered to the old type.
I guess this could be useful for similar cases. The only way to solve it (unless you don't mind deleting entity and updating model from database) is to edit your Entity Data Model as text (by default, DataModel.edmx), locate the entity as <Entity> node inside <Schema> node and find the desired property that indicates the old type. As an example:
<Property Name="MyProperty" Type="int" Nullable="false" />
Simply change Type attribute to the desired type, return to Visual Studio, save the edmx file, and rebuild.
I have an entity (Org) in my Entity Framework that has a foreign key with a table that is in another database (BusinessUnit). We need the foreign key to get the description of the BusinessUnit linked with the Org. In the past (old project without Entity Framework) we were using a stored procedure to return all the information about this entity, including the BusinessUnit description, using a join. So now my problem is how to display the same information than before using Entity Framework.
I've tried, once I load my Org entity from database, to make a loop accessing to BusinessUnit to get the description for each Org, but this is too slow. My other idea was use a store procedure, but I need an extra field on my entity and Entity Frameworks gives me an 3004 error: No mapping specified for my property. I was thinking to use a complex type, but I'm not sure if it's what I need keeping in mind I have to add just a field to my entity. In that case, could I use the complex type just for "select" operations and keep my original entity for the rest of CRUD operations?
How should I proceed?
Thanks.
EF is not able to execute queries across multiple databases. If you need to perform such query you must either use database view and map the view as a new entity (it will be readonly - making it updatable requires mapping insert, update and delete stored procedures) or divide your data querying into two separate parts to load data from both databases. Divided querying can either use two contexts or you can get data from the second database using stored procedure.
The reason why you got the error is that you added the property in EDMX. EDMX can contain only properties mapped to your first database. EDMX generates entity code as partial classes If you need property manually populated from the second database you have to create your partial part (partial class) for entity and add the property in code.
I have an entity/table that uses sqlgeography.
Since EF 4.X doesn't support spatial types I'm instead sending the bytes of the field back and forth.
I have stored procs on the database side that handles the converstion and properties on the code side to do that job.
To add the properties in the code I used a partial class.
One of those properties is for the SqlGeography which simply wraps around the byte[] property to handle getting and setting.
This property is hidden from EF using the NotMappedAttribute.
The other is the property exposing the byte[] itself and is decorated with the EdmScalarPropertyAttribute and DataMemberAttribute.
I then go to the EF model designer (*.edmx) to point the entity model at the Insert/Update/Delete stored procs.
It finds the stored procs alright and realises that they (when appropriate) take a VARBINARY parameter.
It also has a drop down allowing you to select a property on the entity class which maps to that parameter.
However this drop down doesn't list either of my properties. I don't care about the SqlGeography property since that is meant to be hidden from EF, however it is vital for me to be able to point it at the byte[] property, as that is where the data comes from.
I would very much like to avoid database triggers or wrapper classes and addiitonal fields to fudge this in to working.
I tried manually editing the .edmx file to include the byte[] property, but then it just complains it's unmapped.
Can anyone give me some insight in to how to get this to work? Or an alternative method of achiving the end result?
We could use a view to create the binary field for us, but this then involves manually creating a lot of the xml for the relationships within the data.
This pretty much voids the point of using EF which is to make life simple and easy.
For this project We'll just add a binary field to the table then have sprocs to handle the converstion on the server and a property in a partial entity class for exposing the geography type in the model.
Next project I doubt we'll be using EF. Dapper is so much more painless, even if theres a touch more code writing involved.
Here's the links for using views if anyone thinks it would be applicable to them:
http://thedatafarm.com/blog/data-access/yes-you-can-read-and-probably-write-spatial-data-with-entity-framework/
http://smehrozalam.wordpress.com/2009/08/12/entity-framework-creating-a-model-using-views-instead-of-tables/
In the end we created a computed column for each table that exposes the spatial data as bytes.
We then use stored procs for inserting and updating the spatial data.
I am constanstly having problems with model design in MVC. Mostly all of my projects require some entities that are to be created, edited and deleted. Most of these entities have some common properties like creation date, modified date, author, modified by and in some cases even more descriptive properties are common. Because of that I have one single DB table to store them. For instance, Documents table and we store Invoices, Quotations and other business documents in it. I am using Entity Framework v4 for ORM, where we eventually end up with the Document entity.
How do I modify this entity or do I create a separate DocumentViewModel class for it to support multiple document types with common properties (so some form of inheritance or interface implementation should be implemented)? Besides identifying different document types I also need to have some types to have different Data Annotation rules (attributes).
For instance, Document table has PayDate column. Document type Invoice requires PayDate to be provided but document type Quotation does not.
This is the one single problem I am facing over and over with MVC and so far I've been handling it different every time but cannot decide how to properly handle it to achieve the maximum application maintainability and ease of development.
Have you considered making Documents entity abstract?
From the DB side, you will have Documents table containing just the fields shared by all Invoices/Quoations/etc. This field will have an IDENTITY PK - e.g DocId.
In the other tables, additional meta-data specific to that document can be stored, and the PK is a (non-IDENTITY) field DocId, which is also a FK to the Documents table.
On the EF side, Documents becomes an abstract entity, and the other entities inherit from this entity. This allows a nice OO paradigm to exist, and makes your code more robust.
We are currently using this scheme (EF4/SQL Server).
Your scenario sounds very similar to ours - consider using Abstract Classes.
EDIT
Thought i'd add a bit more info to how i've actually implemented this scenario, to put you on the right track.
As the comments to your Q state, we have little knowledge of your domain, therefore it's hard to make informed opinions. Personally, i chose to make my entity abstract, because certain functionality required a "mixed-bag" of items to be returned in one hit. There are other ways to do this of course (such as a stored procedure), but this allows a nice fluent interface between my UI (which is MVC by the way) and my service layer.
Works like this - here's how i get a single Post:
// var is strongly-typed to a "Post"
var somePost = repository.FindSingle(10);
Here's how i get a mixed-bag of Posts:
// var is strongly-typed to a "ICollection<Post>".
// "Title" is a property on my "Post" abstract POCO
var mixedBagOfPosts = repository.FindAll<Post>(p => p.Title = "Some Title");
Here's how i get a collection of "Reviews" (child of Post):
// var is strongly-typed to a "ICollection<Review>"
// "Rating" is a property on my "Review" POCO (derived from Post)
var reviews = repository.FindAll<Review>(r => r.Rating == 5.00);
The kicker is my repository is implemented with generics, and the type parameter ensures type-safety:
ICollection<T> FindAll<T>(Expression<Func<T,bool>> predicate) where T : Post
And it's implemented like this:
return myContext.Posts.OfType<T>.Where(predicate).ToList();
The OfType causes an inner join to the T (which is the child table), so only those records are returned.
Of course, i also have a service layer mediating between my UI and repository, but this should get you on the right track.
Also, you don't have to go with the whole Expression-predicate thing, i like this because it minimizes the number of methods on my interface, and gives full querying power to my controllers, whilst ensuring the queries are deferred to the point of the service layer, but not further.
If you don't like this, you could of course have regular parameters (string title, etc).
As i said, this architecture suited my domain requirements, so it may not necessarily suit yours, but hopefully it gives you some insight.
You can put a table in your EF model many times and just rename them to the entities you need. Just delete the columns you dont need from those.
For example, put in a Documents entity... now rename it to Invoice. Now add another one, and name it Quotation... on the Quotation, click on PayDate and hit the delete key. You can customize these all you want! You can do the same with other ORMs, just takes a little more work. With NHibernate you would manually create the Models, then map them to the same table, but only map what you need.
I am developing StudentApp in .NET 3.5 SP1 MVC Application.
I have two tables
Course
CourseID, course_Name
Students
studentID, student_Name, courseID(fk)
Now I made StudentApp.dbml which is having both table as entities.
As Foreign key will not be present in student entity,
I can not display courseID in student model, more over i can not generate add, edit, list views.
So tell me how to display courseID(fk) in student & i also want course name instead.
And also dropdownbox showing course name & storing courseID in edit view .
I'm pretty sure you have to load the foreign reference for each entity. Since I have no idea how you've constructed your API, I'll have to give you a pseudocode'ish example, but I think this is what you need to do.
List<Students> studList = [your_db_facade].SelectStudents() // Or however you retrieve your students
foreach (Students singleStudent in studList)
singleStudent.Context.CourseReference.Load() //CourseReference.Load() should be in the framework
Then you get the CourseID and name from the single student entity like
singleStudent.Course.CourseID
singleStudent.Course.course_Name
It could look slightly different for you, but I think the key to solving your problem is CourseReference.Load().
If your using LINQ-to-SQL and created a DBML file in Visual Studio then the foreign keys can be listed through the Course property in the Student object (automatically generated so since it is a one-to-many relationship from Student). Sort of like this:
var studentCourseIds =
from s in context.Students
select s.Course.CourseID;
Since your goal is to find the coursename then it is already accessible with Student.Course.course_Name.
Can you post your DBML? Also, DBML is used in LINQ to SQL (L2S) - EDMX is the mapping used in the ADO Entity Framework. Are you using LINQ to SQL or the Entity Framework (EF)?
No matter which one you are using - they both support Foreign Keys and you would get a property representing either side of the relationship - you don't need to do anything special (the Foreign Key must exist in the database, of course).
In EF, the foreign keys are called "navigtion properties" and they work a little differently to Foreign Keys in L2S. Nothing major, but updating them and "eager loading" are somewhat different.
Just drop the tables onto the map in the designer in Visual Studio (or generate using command line equivalents if you prefer).
Regarding Foreign Keys and Drop Down Lists (and other UI goodness) - I wrote a couple of blog entries on some approaches which might suit you. One part is located here and part two is located here.
if you create the correct relationship in your SQL server database, then when you add the tables to your DBML designer, the relationships will be copied across also and your code will link up automatically.