Entity Framework and relationships in Vb

[Signalman]

I have recently being following the various tutorials on creating models in the entity framework and reading them with vb code.

I have managed to create a model and add the relationships between the tables in the model.

These can be one to one, one to many etc.

What I can't understand is when the relationship is set between the tables, what are keys used to link the two tables.

The properties for the link simply shows the other table and not the two fields.

Whilst I many not be understanding it correctly, I am expecting the value in one table to be looked up (as the key) in the next table ?

[jmcilhinney]

I'm not 100% sure what you're asking but I'll post a couple of diagrams that hopefully show how relationships work in the database and in the EF model. Here's a screenshot of a diagram of a SQL Server database with 7 tables. I've lined up the table to show exactly which columns are related to which.

The first two tables are engaged in a 1:1 relationship, with the primary key of the child table also being a foreign key from the parent table. The next two tables are engaged in a 1:many relationship, with the child table having its own PK and another column that is a FK from the parent table. The last three tables are engaged in a many:many relationship created from two 1:many relationships, with the join table existing solely to contain a FK from each of the sibling tables in the relationship. Here's how that looks in the EF designer:

That EF model is in VS 2012. Notice that, when selecting the relationship between Parent1ToM and Child1ToM, it highlights all the properties involved.

[Signalman]

Thanks for spending the time to create the example, this is most helpful, however am correct in assuming that when creating the relationship / association in the entity model, it's always best to create foreign keys.

Also, when the relationship / association is created, whilst I can see that it is created between the tables, in your example, there are identical field names in both files. As such I assume that the link / relationship between the two files in based on values in these fields 'matching'

However looking at the model, and the link property's, I can't see where the field names that form the relationship are specified.

The example i am looking at, does not seem to have the same field names in both tables, and when I add a advocation, it crates a foreign key, and adds an exa field to one for the tables.

However again how do I see what the fields are that the relationship / association is between ?

Also when adding records to the file with foreign keys, do I have to manually update the addition field or is it automatically taken care of ?

Many thanks for your help