Model Defined Functions

re: Model Defined Functions

efNewbie — Fri, 12 Feb 2010 20:08:25 GMT

First off . . . I am a complete newbie to "APPLIED" EF (read about, seen it at Code Camp).

After a not terribly painful week . . .

I have the EF implemented in a grid for a very basic header-detail (2 tables).

I am however feeling a bit nervous re: can the EF do all we need.

I read people who trash EF as not ready for prime time . . . as a ½-way there technology.

Here's where I stand in the trench at the moment . . .

The detail records are presented in a asp:GridView

with ['Edit' 'Delete' 'Select'] in the leftmost column.

'Edit' works (though the hiding of columns appears to only be doable following setting the DataSource).

Is there a way in the EDMX mapping to leave out columns. Apparently no . . . all columns MUST be mapped.

'Delete' works . . . but how to 'Delete Confirm ?'. Javascript ?

'Select' . . . I don't understand. What is it doing ? How do I wire an imported function to 'Select'.

My current biggest hurdle of the moment is how to 'filter' the Select sproc.

I am right now struggling with try to accomplish filtering based on several DropDownLists on the form

by passing parameters to the .Where of the ObjectQuery, but the .Execute is failing:

"'tblTable.FieldName' could not be resolved in the current scope or

context. Make sure that all referenced variables are in scope, that required

schemas are loaded, and that namespaces are referenced correctly., near

multipart identifier, line 6, column 47."

re: Model Defined Functions

Daniel Simmons — Thu, 14 May 2009 17:31:16 GMT

@Muhammad,

These functions are just used to give the function signature for us to figure out how to translate into a part of the overall query sent to the server. As such the return type does not need to be IQueryable--it can be just IEnumerable.

Once the query has been executed and the results returned, if the results are entities, then lazy loading will work the same as for any other entities. Eager loading can also work because this is just a rewrite over the query to bring along extra data.

Yes, it will work fine for whatever entities you have--POCO or non-POCO.

- Danny

Entity Framework: функции определенные в модели

progg.ru — Thu, 14 May 2009 16:21:10 GMT

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re: Model Defined Functions

Muhammad Mosa — Thu, 14 May 2009 11:01:38 GMT

As this going to support Linq, the return type of Fucntions that return collection would be of type IQueryable right?

Also in case function return colletion of entities does eager and lazy loading work on this case?!

I also assume it will support POCO entities by default! Am I right?

Entity Framework Design : Model Defined Functions

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re: Model Defined Functions

Bruno Santos — Tue, 03 Mar 2009 20:59:16 GMT

Hi. That's a great post! Its exacly what I wanted.

The problem is, it seems the atribute doesn't exist in the VB.NET is that possible?

I can only find 2 sites exposing this subject, yours and this:

http://blogs.msdn.com/efdesign/archive/2008/10/08/edm-and-store-functions-exposed-in-linq.aspx

Update on Computed Properties

Entity Framework Design — Tue, 13 Jan 2009 07:27:41 GMT

A while back I wrote a post that introduced the concept of Computed Properties . Since that time we’ve

re: Model Defined Functions

efdesign — Mon, 12 Jan 2009 05:29:49 GMT

Shawn,

Well it is not something we have done yet. But it is something we are considering. All we need to do is allow the [EdmFunction] attribute on properties and treat the declaring class as the first parameter in the MDF implicitly

Sort of like the reverse of Extension Methods I suppose.

Cheers

Alex

re: Model Defined Functions

shawn — Sun, 11 Jan 2009 00:09:15 GMT

Would it be possible to do this for non-static functions as well, so that you can write the queries in a more object-oriented way? So instead of:

var peopleOver21 =

from p in ctx.People

where GetAge(p) > 21

select p;

Could you map it such that you could query like this:

var peopleOver21 =

from p in ctx.People

where p.Age > 21

select p;

That way you are calling p.Age instead of GetAge(p)? It seems like that would be a cleaner, more OO way to consume the data in many cases.

re: Model Defined Functions

efdesign — Sat, 10 Jan 2009 01:21:44 GMT

Julie,

I'm sure some will complain. We all have different ideas about how things should be done.

Personally I don't see the conceptual difference between a Model Defined Function and WebService end point. The only difference is that the Entity Framework automatically handles calls to the MDFs.

And given that you can write Model Declared Functions too (i.e. no definition) you can separate out the implementation from the declaration too, if you think that is important.

If you do that of course, then you need to handle calls to the function yourself.

Am I making any sense?

Alex