Our company is in the middle of evaluating a couple of different ORMs and we are currently looking at the EF4 side of things.
I have a small question that I hope someone here can answer...
In our generated EntityDataModel.Designer.cs file all our Entity classes (and the properties within them) have a ///summary with the sentence "No Metadata Documentation available".
Is there any way to have these picked up from the Description Property on the columns from SQL Server?
I can see there is a documentation property within the edmx file but they are all blank.
Obviously its not a deal breaker in our decision - but it would be nice.
Thanks for any advice
Aaron.
Yes, documentation properties are blank in EDMX because you must fill them yourselves. EF doesn't load columns descriptions defined in SQL Server.
These columns descriptions are stored in sys.extended_properties and have MS_Description as a name. Theoretically you can modify T4 template (EFv4) to load descriptions for columns and create comments but it would be a lot of work to do. You will have to:
for each scalar property you will have to search metadata to get column and table name and query DB to get a description
That is a lot of work and having T4 template opening connection to database is very uncommon.
Related
I'm trying to create a datamodel in the Oracle Data Modeler module that is available in Oracle SQL Developer. I would like to maintain my data dictionary from this model. To do this (I think) I need a generated DDL file for which the attributes are not longer than 30 characters.
I have just discovered Oracle SQL Developer and am completely new to creating these kind of models. What I have done so far. I have created a logical model and have engineered it to a relational model. From the relational model I can then generate DDL scripts that I can run on the database to make the changes I want.
When doing this I run into a problem. When engineering the logical model to a relational model I can see that the foreign keys I have made become more than 30 characters. This is because it seems to generate the name as (see picture)
From searching it seems you should be able to fix this with naming standard templates. I have looked for this menu option but can't find it. I have found the name abbreviations functionality for which you can upload .csv files but I think this is for something different.
Rightclicking on the logical model in the datamodeler browser view gives me the opportunity to Apply naming standards, but this gives me a message that I should turn off the keep as the name of the originating attribute option (see picture). I have looked for this but can't find this option.
My version of Oracle SQL Developer is 4.1.3.20, Build MAIN-20.78.
Please let me know if my story is not clear. Thanks.
Generated column name
Applying name standards message
You will find the option under Tools/Preferences/Data Modeler/Model/Logical
I using Entity Framework 6, Code First. I have a data entity with several properties. One of this properties is string property named "Indexing".
The only use of "Indexing" property is to help find specific entities based on given keywords. I running Full Text Search query and looking for entities with specific keys in their "Indexing" property. Usually "Indexing" is a large bunch of text, describing various aspect of entity. After I find entity, I have no use of "Indexing" anymore.
Right now when I executing my "where" query, the entity is loaded and it including "Indexing" property loaded as well. This is a waste, since I really have no reason to load all this text from database and bring it to server.
Question: How I can use "Indexing" property for search, but to avoid bringing this data to server?
Actually that was a dumb question, I realized it right after Vlad274 comment. Simple "Select" does exactly what I needed...
I'm working with a legacy database that I can't easily create an entity model over because it uses extension tables with what is effectively composite keys and EF only supports single column keys for mapping one entity to multiple tables.
So, what I've decided to do is create updatable views (with INSTEAD OF triggers to handle CRUD operations) over the top of the legacy tables (which cannot be touched) and then have my entity model (either using EF or DevExpress XPO) built on top of the database views. This will also allow me to do stuff like easily add sub-queries in the select clause to retrieve child counts on parent records when retrieving a list of parent records in a single query.
However, I don't particularly want to manually write the SQL for all the views and triggers so I thought I'd use data model defined in the .EDMX file and t4 templates to help me generate the bulk of the T-SQL needed to create the views and the triggers. I thought there would be some template that I could use as the basis for doing this, but seems that's not so easy to find.
Can someone please suggest a t4 template that I could use as the basis where mappings are being retrieved from the .EDMX. Alternatively can anyone advise how to use the StorageMappingItemCollection to retrieve the mapping information from the EDMX file. I know a few people have said that apparently you can't use it or that they just use Linq to Xml, but I would have thought it should certainly be possible to use the StorageMappingItemCollection class as a strongly typed class to access this data.
Any examples of how I could use StorageMappingItemCollection to access mapping info would be very helpful. Thanks.
See http://brewdawg.github.io/Tiraggo.Edmx/ you can install it via NuGet within Visual Studio and it serves up all of the metadata from your EDMX files that Microsoft hides from you, very simple, works great.
Something changes or it still not support this?
For example join database1.dbo.Users and database2.dbo.Addresses
I actually did find a way to make an EF model span multiple databases if your database supports Synonyms. Basically you setup Synonyms to Database2 on Database1, create separate edmx models for each, then merge the XML
I posted the exact steps to make an edmx file span multiple databases here if you're interested, along with a script to do the merge for you whenever something changes.
I think what ais asked is if you can join tables from different databases, not different providers, resulting in one entity mapped to two or more tables or views from different databases.
If you think about it, when you create a EDM model with Visual Studio it ask you to give an existing database, and when finished creating the model, it generates an EF connection string, that internally address to the given underlying database connection string.
E.g: metadata=res:///EFTestModel.csdl|res:///EFTestModel.ssdl|res:///EFTestModel.msl;provider=System.Data.SqlClient;provider connection string="Data Source=.\;Initial Catalog=EFTest;Integrated Security=True;MultipleActiveResultSets=True"*
So each model matches only a database, only a connection string.
EF4 still does not support creating one conceptual model which works with N storage models. At least this is not supported with any built-in provider. Perhaps in the future this could be done through a new provider that combines the support of many storages (from the same providers or different).
I havent done enough research on it, but perhaps Windows Server AppFabric (Codename Velocity) could be the bridge to go through this gap.
Note: I have tried even editing manually the xml for the EDM (edmx) to insert a second element inside the <edmx:StorageModels> tag but it does not match the EDM XML Schema so VS warns about it:
Error 10021: Duplicated Schema element encountered.
Rafa Ortega
MAP2010
See answer to similar question:
Entity Framework - Inserting entity with multiple models and databases
I have a database that I wish to build an EF model from, however I do not want to include certain columns from the database as the columns concerned are maintained exclusively on the server and should not be manipulated by any application.
Both of the columns are DateTime (if this makes any difference), one of the columns is nullable and is maintained by a trigger on updates and the other is not nullable and set using a default value in the table definition.
I guess I am looking for something like the "Server Generated" option in Linq2Sql; but I cannot find such an option.
Can anybody tell me how to work around this?
Caveat:
I have been trying to introduce business object modelling at my place of work for some years and it has always been rejected because of the amount of additional code that has to be hand-cranked. EF is currently being seen as a viable solution because of the designer and code generation therefore any option that involves hand-cranking the XML will only turn the rest of my colleagues away from EF. I am therefore looking for something that can be done either using the designer or using code.
EDIT:
I guess that what I am looking for here is either...
(a) a way to create the model without EF referencing the columns in the store (ssdl) and therefore not looking to manipulate it in any way
(b) a way to programatically set the "StoreGeneratedPattern" attribute against the property when I create the ObjectContext (the easy answer is to manually manipulate this in the .ssdl, but this would then be overwritten if I refreshed the model from the database and I cannot go down the route where the .csdl, .msl & .ssdl are hand-cranked).
Can you do this with the Entity Framework? Yes; it's easy. Can you do this with the Entity Framework designer? Unfortunately, that is much harder.
The problem you're having is that the column exists in the storage schema (SSDL) in your EDMX. Removing the column with the GUI designer simply removes it from the client schema, not the mapping or the storage schema. However, it's simple enough to go into the EDMX and remove it. Having done that, you can also remove it from the mapping in the client schema portions of the EDMX, and the entity framework will longer complain that it is unmapped.
Problem solved, right?
Well, no. When you use the GUI designer to update the EDMX from the database, the storage schema is thrown away and re-generated. So your column will come back. As far as I know, there is no way to tell the GUI designer to never map a particular column. So you will have to re-do this every time you update with the GUI designer. Fortunately, the EDMX is XML, so you can do this with a XML transform, LINQ, or the XML tool of your choice.
Can you not create a view with the columns you need and import it through entity function wizard and map it to your entities?
You could modify the text template to ignore these columns when generating your entity classes. For example if you added "IGNORE" to the documentation summary, you could modify the template to ignore them by replacing;
Dim simpleProperties as IEnumerable(Of EdmProperty) = typeMapper.GetSimpleProperties(entity)
with;
Dim simpleProperties as IEnumerable(Of EdmProperty) = typeMapper.GetSimpleProperties(entity).Where(Function(p) p.Documentation is nothing orelse p.Documentation.Summary.IndexOf("IGNORE")<0)
Right click on the field in the graphical representation and choose delete. Ive found that sometimes you will get errors when you make a lot of changes to the modeling at once and start to lose track of your changes. Your best bet might be to rebuild the EF generated model.
Keep in mind that when you "update from the database", that old fields on the generated models will not be removed, you will have to remove them manually. For example if you renamed DateField1 to DateField2 in your database, and then you "Update Model from Database", you will now see both DateField1 and DateField2 on the resultant model. This can be a cause of errors.
Do you not want the column to appear in the model at all?
Try selecting the column in the Designer view and hitting the delete key.
Edit
You could make the setter for the property private. Then your app won't be able to modify the value.
Timestamp is a different data type than DateTime. Timestamp seems to be recognized as an attribute the engine manages, much like an identity attribute. You can't "update" a timestamp attribute. Hence, the EDM can manage it correctly (just as it does an identity).
In EDMX designer, select the property and set StoreGeneratedPattern to Computed.