I did work on ADO.NET Entity Framework v2 about two years ago. I have faint memories.
Incidentally, I happen to be working in a very secured (for want of a euphemism) environment where a lot of links are blocked and there’s not much one can do. It does get in the way of studying and working, more than a bit.
Therefore, I have to rely on this forum for a few basic questions I have to get started again. This time, I am working on Entity Framework 4. Here are my questions.
All these questions relate to the EDM generated entities, i.e. not the Code First model.
1) Is my understanding correct? I can rename any column name in the EDM designer generated model and nothing breaks.
2) Foreign keys are expressed as navigational properties in the generated entity classes. No special consideration is required to maintain foreign key relationships. I recall in version 1 of EF, you had just ID properties and the navigational IQueryable/IEnumerable/EntityCollection/RelatedEnd properties were introduced in version 2. I just need to know if I need to do anything to retain/maintain foreign key relationships and referential data integrity. I assume I don’t need to. A confirmation would be nice.
3) What are all the possible ways to execute a stored procedure? I recall — one way to use ExecuteSQL or something on the Context.Database object, another to use EntityClient API and the third was to specify stored procedure names in the InsertCommand, SelectCommand, etc. thingies in the mapping window of the EDM designer. Is this correct?
4) How do you use those SelectCommand thingies in the mapping window on an entity? Do you just supply the names of the stored procedures or user defined SQL functions?
5) How do I create an entity out of a subset of a table? Do I just create an entity from the table and then delete the columns I don’t need from the designer? What happens if there are required (NOT NULL in SQL) values that are not in the subset I choose?
6) How do I create a table out of a query or join of two or more tables.
1) You can rename columns in the designer and nothing should break (if the name is valid)
2) Navigation properties point to related entities. In EF4 foreign keys were added. Foreign key properties basically expose the database way of handling relations. However, they are helpful since you don’t have to load related entities just to change relationship – you can just change the key value to the id of the other entity and save your changes
3) Yes. You can either execute the procedure directly – this is for stored procedures that are not related to CUD (Create/Update/Delete) operations. You can map CUD operations to stored procedure as opposed to having EF execute SQL statements it came up with for your CUD operations.
4) I think this is a bit out of scope – you probably can find a lot of blogs with images how to do it. Any decent book on EF should also have a chapter (or two) on this. Post a question to stackoverflow if you hit a specific problem.
5) Remove properties in the designer and then supply default value to the S-Space definition. I believe you cannot do this with the designer. You need to rightclick on the edmx file and open it with the Xml editor and manually edit it. Also see this: Issue in EF, mapping fragment,no default value and is not nullable
6) You can either create a view in the database or you can create entity set using E-SQL in your edmx file (I think this will be read only though) or you may be able to use Entity Splitting. Each of these is probably a big topic itself so I think you should find more about these and come back if you have more specific questions / problems