Click here to see how to do it while using a code first approach. Below the original database first approach question and answer.
I am using Entity Designer to create a database first model. Now I want to create a foreign key relationship between ProductId and ProductId (see below). I looked at the "add new association" but I cannot connect the two items. Can someone more experienced tell me how to accomplish this?
According to Relationships/Associations with the EF Designer, the steps to create a foreign key association are:
Right-click an empty area of the design surface, point to Add New, and select Association….
Fill in the settings for the association in the Add Association dialog.
...being sure to check the Add foreign key properties to the Entity checkbox when filling in the relationship details.
See also: Relationships, Navigation Properties, and Foreign Keys
If you are using the database first approach, it's better to create the foreign key on the database and update the model. Of course, this is true if you can modify the database; if not, you're stuck with the option of creating the referential constraint on the model.
To answer the bonus question:
If you have SQL Management Studio installed then you can very easily use the Database Migration wizard (right click on a database, "Tasks", "Deploy Database to SQL Azure") and from there fill the textboxes with the required information that you get from Azure.
Also, make sure to add your IP to the ignore list in Azure or else you won't be able to upload. This can be done in the Azure webportal.
Related
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
I've been using EF for a while (4 with model first) and so far I've not created any mapping manually. Whenever I need more entities/tables, I add an entity and the associations (all foreign key) and click "update database from model", which, as is well known, doesn't update any database from the model (although it does need a database connection for reasons I don't know). What it does is generating a storage model and the appropriate mappings to it, which are all stored back to the same edmx xml file.
So far, that has always been enough for me but I'm wondering what the workflow would be if one is to tweak the mappings and storage model manually. "Update database from model" overwrites all manual customization - so how is one to fix most of the mappings and storage model? Because I clearly don't want to do it all by hand - in fact I couldn't even figure out how to actually create a table in the storage model other than by editing the edmx in the xml.
I have the same problem. I just use a mixture of methods. If I add a field to the database, I just add the field to the model file. If I do a major restructure, I delete the table and recreate it by generating it from the database. Sometimes, I actually edit the edmx as XML to change or add things. You just kinda gotta figure out what process works best for you. I have managed to avoid heavy customization in the edmx by using the T4 template or changing the database and regenerating.
I've been trying to find the answer to this question here. Several people seem to ask similar things, but I don't get the answers. I have an EF entity with a bunch of child entities (one-to-many relationship). I want to be able to delete the "parent" entity and have all the child entities deleted at the same time.
Some people mention "Cascade Delete" should be set on both EF model and database (Sql Server in my case). The problem is:
I have absolutely no idea how to do this (seems to be implied in those answers that you should know, but sorry...)
I have a feeling I've run into a similar problems before and found an answer somewhere that was simpler than setting this Cascade Delete. I may be wrong, maybe it is the only way, but if there is a simpler solution I'd like to know.
In either case, a clear example of how to get this working would be greatly appreciated!
In SQL Managment Studio go to your database and find the table where there should be a foreign key. Add a foreign key to the table pointing to the other table. I assume you know how to setup a foreign key. In the foreign key setup at the bottom of the dialog window you'll see a Delete property. Set it to Cascade. This will cause any dependent rows to be deleted whenever the parent row is deleted. Then go and update your data model in Visual Studio. Everything should be setup for you now.
Here is some relevant documentation on MSDN. Note though that there appears to be an error in the example. I received the following error from the EDMX designer when using this configuration.
Operations cannot be specified on ends with multiplicity '*'.
You should set the OnDelete property to Cascade for the end will be triggering deletes on the other end.
As an example, in a relationship involving customers and orders where you would like to have a customer's orders deleted along with the customer, you should set the OnDelete property for the Customer role to Cascade.
Note that only objects that have been loaded into the ObjectContext will be affected by a cascading delete. You will be relying on the cascading delete that you set in the database to look after any other records.
I see some posts on programmatically mapping a table with a composite key but I haven't found any examples to do that within xml of the edmx file. How do I do this? In the edmx of my entity type I have a key section with multiple propertyref's pointing to my composite key. However, when I go to save my changes it errors and states that there is no update function.
It seems to me, if I mark one key as the primary key and it can manage that it should be able to use a composite key as well.
Please do not reply and state that I shouldn't be using composite keys because I don't care and have no ability to change it. I didn't develop this database as it is a third-party ERP application that I'm interfacing with.
From what I can tell I may have to create a stored procedure just to save it? Isn't there a better way?
Thank You.
Maybe im just an idiot, but I am having serious issues mapping relationships with the new entity framework.
When using LinqToSql, you would just right click the table, add association, select the two tables, and selected the property from each table the association was based on. End of story, it worked perfectly.
Using the entity framework and the slightly different visual editor, I go about doing the same thing, but there is no option in the initial association menu to select the actual properties. So after that, you bring up the association map, and thats where the problems start... What the hell? The only thing you can edit in here is the column to which a key is mapped, but the only columns you can choose are those in the same table as the key... Im completely lost.
Instead of mapping the association in the designer, try setting up your foreign key constraints on your tables then update the model from the database and the associations will be setup for you.
There is no possibility to map association end to an incomplete Entity Key.
This is an Entity Framework limitation.