Question

I have an edmx file that reflects 100% my DB schema.
Along with this I need to create some custom Entities based on the existent, pretty much like a view that will aggregate fields of several entites into a single one.

The problem is that this isn’t quite working. I tried several approaches but it always gave me conflicts with the actual entites already on the edmx.

I need to have those entities that reflect my DB schema, so do I have to create another edmx file to hold my custom entites and avoid colisions?

I also though of:

• create a stored procedure but then if
  I need to filter the SP result I
  eather have to add support for serach
  on the SP of get all the rows and
  filter with Linq2Objects… won’t do
  this!
• create a View, and this one would
  work pretty well but I want to try
  to do this making use of the EF4
  designer and keep everything in one
  place.

Could anyone point me to some examples?

Answer 1

You can’t define two entities based on same table except special cases (table splitting, hiearchy mapping). In this case you have to use DefiningQuery as @James suggested or QueryView. The difference is that DefiningQuery is defined in storage model and it is common SQL. QueryView is defined in conceptual model and it is ESQL defined on top of already existing entities. QueryView supports only some features of ESQL (for example it doesn’t support aggregate functions). In both cases you have to modify EDMX directly (XML), these features are not supported in designer.

Database view mentioned by @James is also an option if you don’t want to use these advanced EF features. You can as well simply expose predefined queries on your object context and map return projection to custom type.

Be aware that neither of these methods will allow you to modify, insert or delete data.