I am trying to use EF with an existing DB. I brought in a Client table into my data model and let EF create a Client entity. I have a sproc, GetClientSearch, that only returns 5 out of the 15 columns from the Client table becuase that is all that is needed for that call.
Here's what I've done so far:
Added the sproc to Function Imports and set the proc to map to the Client entity.
When I execute the proc through the Context, I get "The data reader is incompatible with the specified 'GAINABSModel.Client'. A member of the type, 'MiddleInitial', does not have a corresponding column in the data reader with the same name." exception. (MiddleInitial is not one of the columns returned in the proc)
I know that I can create a new entity that maps to the proc, but I don't want to do that for every proc I have to import into my model.
Given that the DB is currently in use in production, changing stored procs to map to my current entities may not be an option.
Currently using EF 4 and VS 2010.
So, is there a way to map the results of the sproc to the Client entity, even though the columns returned are not 1:1 with the properties of the EF entity?
Yep, one of my many pain points in EF.
If you can't modify the SP's, your best bet might be to create "wrapper" SP's on top of the existing SP's.
In other words, EF-serving SP's that call into the existing ones, and return NULL for the columns you don't need, but are required for the entity.
Of course the better option would be to create the entities properly.
Another option is to use ObjectContext.Translate<T>, which basically performs a L-R between the SPROC results and the entity you supply.
If the result set doesn't contain the field, then the property on the object will be null.
Which is probably what you want.
Am running into the same Issues. Suppose i have UserEntity created out of the User Table and have 3 procedures.
AuthenticateUser - returns 4 columns from the user table after authentication
RetriveUser - Returns 10 columns from the user table
GetUserName - return UserID and UserName only for dropdown purpose.
If we create different entities for each of the different SP. It would result in bad design because of duplication.
I have no other way of using same entity for all these SP's.
Overall, i don't recommend entity framework atleast for legacy applications in production.(where you can not update your Sp's also.)
Related
I have two tables wherein i want to insert the data to the first one (MASTER) and the other table would copy some of the data from the Master table..
Here is my representation:
I want the Ven_ID to also be reflected in my Workflow table Workflow_ReqID automatically.
I know this is possible but can someone give me the directions ?
You can have a trigger/procedure at database level which will insert data into your second table. It depends if this table is updated anywhere else.
There are two ways to go about it :
Use SQL Server AFTER INSERT Trigger. You can find plenty of resources off the internet on how to create a trigger and how to declare its definition.
Another way to do it is through entity framework (I see you have tagged entityframework)
I will explain how you can use entity framework
Let's say you have the entity representing the WorkFlow table as WorkFlow and the table representing Ven (may be vendor) as Vendor.
Since you are having required foreign key in the WorkFlow table of the Vendor primary key, you must have a backing stub for that i.e. your WorkFlow table must have a virtual navigational property of type Vendor i.e.
public class WorkFlow
{
//other properties
public virtual Vendor Vendor{get;set;}
}
you just have to create WorkFlow object and the Vendor object (either create a new or retreive from db) and just assign it to the workflow object i.e.
WorkFlowObj.Vendor = objVendor
and EntityFramework will take care of rest.
I would prefer this way.
Though using triggers is not bad, but only problem with them is when you have to deploy, you must also deploy them triggers and every time you make changes to them, you must take care of them too.
If you want Ven_ID and Workflow_ReqID to be same get the Vent_ID in the output parameter in store procedure and pass it to the second table insert statement.
Get last inserted id using SCOPE_IDENTITY() after insertion and add it to workflow table. To save db trip you can use sproc for that.
I was reading this article http://blogs.msdn.com/b/adonet/archive/2011/01/27/using-dbcontext-in-ef-feature-ctp5-part-2-connections-and-models.aspx and was trying to figure out how to create private setters (the section in the article DbContext with read-only set properties is right before the summary). How would you create private setters? I was playing around with different methods but nothing seemed to work. I am doing this because I need to group the original table based on a query I have because the original table is a heap and I need a primary key for the entity. So anytime a client asks for this table it is already grouped. Not even sure if this is the correct way to do that. Thanks.
EDIT: sorry for being vague. I am doing code first. For example there exists a SQL Table with JobNbr, Qty and Date and I need to group by JobNumber, sum on Qty and take the oldest expiration date, and that will be my entity since this table has no primary key. The way I am doing it now gives me the error below from a method I created in the DbContext class. I do have a EntityTypeConfiguration class. Do I do this in that class?
EDIT: : you might be wondering why I am doing this. Basically I need to get data from the heap and save it in another database. My original approach was database.SqlQuery() to get grouped rows from the heap, but sometimes I have too many parameters for execute_sql. So I decided to create an entity for the grouped query without tracking changes (since all I am doing is reading from the table and saving to another DB). See my post here with the issue I am having https://stackoverflow.com/questions/22106030/entity-framework-6-this-database-sqlquery-character-limitation-with-sp-executes. The only way I know to get around it is to create an entity (even though in this case the entity is a query and not a table).
The entity or complex type
' cannot be
constructed in a LINQ to Entities query.
I have my framework setup with code first with a BaseEntity type that simply contains Id and a Name properties (all my db tables have at least these two fields). The problem is that the db was written before we implemented EF so many of the columnnames in the db do not match this nice Id/Name convention (for example there might be CustomerId and CustomerName etc). Now as far basic CRUD operations go this works fine because I simply do this in my mappings:
this.HasKey(t => t.Id).Property(t => t.Id).HasColumnName("CustomerId");
and it correctly maps from one to another and all is good
However, we also have some complex database logic that can only be encapsulated in stored procedures so in my ObjectContext I have a generic method for invoking sprocs that returns IList and allows you to pass in the name of the proc to invoke and any params it requires, it then goes to the underlying Database object on the ObjectContext to make the call. This works great for classes where the property names in the poco match those in the db, but if they do not, it ignores any mapping I have setup for that object (see above) and I get an error like this:
The data reader is incompatible with the specified 'SomeNamespace.Customer'.
A member of the type, 'Id', does not have a corresponding column in the data
reader with the same name.
Is there any clean way to work around this or to properly instruct it to map it correctly on the underlying datareader?
thanks
I have these two related tables Client (ClientId, Name) and ClientDescription (ClientDescriptionId, (FK) ClientId, Description). That is to say each Client can have many associated descriptions. Now, when displaying the a list of ClientDescriptions, I also need to know what the Name of it's associated Client is.
Now you'll probably say that I allready have this information, since I can simply follow my navigation property back to the associated Client and use its Name. I can't do that because I'm autogenerating a grid in Ria services, and this just gives me a count for navigation properties, and I haven't found a way to flatten this down in my metadata file. Hence why I want a property.
The whole idea is that I want to be able to add a new field to my database, update my entity classes from the database and regenerate my domain service, and the new field should just pop up in my grid. I shouldn't have to update my xaml just because my database happen to have an extra field.
So, what I would like to do is add a ClientName field to the entity (clr object), but keep my database clean (no such denormalization in the db).
So, I generated my edmx, and added a new property named ClientName. Set it to StoreGeneratedPattern.Computed, and compiled. I then get a nasty little error
Error 3004: Problem in mapping fragments starting at line NN: No mapping specified for properties (etc..)
The solution apparently is to generate my database from my edmx. (Or that's what answers to questions about that error seems to yield.) But this generates an actual DB-field, which I don't want, so that answer doesn't apply to my case.
So my question is: How can I denormalize my clr entity, but keep my db tables normalized?
Edit: I guess this question can be generalized a bit. The issue would be the same if ClientDescription contained a few numeric fields that I wanted to do some calculations on, and I wanted the result available as a field and the algorithm should be in c# rather than in my database.
To answer your more generalized question:
Entities are generated by the Entity Framework with a partial keyword.
This means that the code of an entity can be split in multiple source files in the same namespace and assembly. One will contain the generated code from the Entity Framework, the other will contain custom properties and methods.
If for example, your entity has the database fields Price and Amount you could add a property in the partial class TotalPrice which would return Price * Amount.
Then the algorithm will be C# and your database won't know about the extra property.
I need to dynamically access some SQL tables hopefully using the Entity Framework. Here's some pseudo code:
var Account = DB.Accounts.SingleOrDefault(x => x.ID == 12345);
which will return me an Account object and this contains some fields called "PREFIX", "CAMPAIGN ID" and further information about the accounts are stored in separate SQL tables with the naming convention of PREFIX_CAMPAIGNID_MAIN.
The tables all have the same fields so I was thinking of creating a new Entity that isn't mapped anywhere and then dynamically loading it, like so:
var STA01_MAIN = new MyAccount(); // my "un-mapped" entity
DB.LoadTable('STA01_MAIN').LoadInto(STA01_MAIN);
I can now get anything about the STA01_MAIN account: STA01_MAIN.AccountId.
So my question is: how do I access these tables using the Entity Framework?
I don't think EF has a LoadTable and LoadInto method, but ObjectOntext.ExecuteStoreQuery might be what you're looking for:
http://msdn.microsoft.com/en-us/library/dd487208.aspx
This should let you execute an arbitrary query against your database, and then map the results to an arbitrary type that you specify (even if it's not otherwise mapped in EF).
It goes without saying that you would be responsible for putting together a query that supplied the necessary columns for mapping into the destination type, and also adjusting said query when this type changes.
Here's some further discussion concerning its usage
http://social.msdn.microsoft.com/Forums/en-US/adonetefx/thread/44cf5582-63f8-4f81-8029-7b43469c028d/
Have you considered mapping all of these tables (with the identical columns) into an inheritance relationship in EF, and then querying them as
db.BaseTypes.OfType<SpecificType>().Where(/*.....*/);