A ‘Many To Many’ field template for Dynamic Data

re: A ‘Many To Many’ field template for Dynamic Data

Shail — Mon, 27 Oct 2008 10:58:59 GMT

Hello David,

This is really helpful. I was looking for it and you can at right time. Thanks

Any Idea, that this will be supported in LINQ to SQL sometime ?

Shail

re: A ‘Many To Many’ field template for Dynamic Data

Tom Pester — Mon, 27 Oct 2008 11:16:54 GMT

Thanks for making Dynamic Data more complete David !

I think this is one of the 3 missing features that were missing in V1

1. Not able to reorder columns (in detail & list view)

2. No support for many to many relations

3. No support for creating a lookup inline. Eg. If I create a Product and I have to specify a Category for it that doesn't exist yet I have to abort the Product creation, go and create a Category and start creating a Product again.

This is a usability problem that can be adressed by creating the Category on the same page the user creates the Product. So the Category is effectivly created "inline"

I know point 1 is going to get introduced in V2 and I hope you will consider point 3 as well!

This would cover almost 90% of the requirments I typicaly have and I would recommend it wholeheartedly to my team.

I have some feedback on the Many to Many support :

- The list can get pretty long so I would wrap it inside a div and give it a css property of "overflow:scroll" so that the user the vertical height can be controlled;

- Give the developer the option to split the checkboxes in x columns

- Give the developer the option order left to right or top to bottom

Also, Is there a book on Dynamic Data in the pipeline that you know of?

re: A ‘Many To Many’ field template for Dynamic Data

Buckley — Mon, 27 Oct 2008 11:27:16 GMT

Is this template evailable in the latest codeplex release?

re: A ‘Many To Many’ field template for Dynamic Data

davidebb — Mon, 27 Oct 2008 22:18:32 GMT

Shail, I'm not aware of plans to add Many To Many support to Linq To Sql. Geneally, Linq To Sql is a simpler/lighter technology, which does not have the same power of abstraction as Entity Framework.

Of course, theoretically it may be possible to make this work in Dynamic Data by directly dealing with the 'Junction' table in the field template, though that might be non-trivial.

re: A ‘Many To Many’ field template for Dynamic Data

davidebb — Mon, 27 Oct 2008 22:25:50 GMT

Tom, thanks for all the feedback. Note that all the styling related changes you bring up (overflow scroll, # of columns, left to right) are things that can be done simply by changing ManyToMany_Edit.ascx (which has the CheckBoxList). Though of course, if the goal is to use different settings for different fields in the same app, it might make sense to create a metadata attribute that would pass that information in from the model to the field template.

For your other points that don't directly relate to Many To Many, I would prefer to start a new discussion on the Dynamic Data forum, in order to keep this post focused on just Many To Many :) Thanks!

re: A ‘Many To Many’ field template for Dynamic Data

davidebb — Mon, 27 Oct 2008 22:29:29 GMT

Buckley, right now it is only available here, but it should make its way on to Codeplex at some point (and eventually in our next release).

re: A ‘Many To Many’ field template for Dynamic Data

Mike — Mon, 27 Oct 2008 22:58:52 GMT

"I'm not aware of plans to add Many To Many support to Linq To Sql"

That was definitely announced way back, just as support for other providers.

re: A ‘Many To Many’ field template for Dynamic Data

davidebb — Mon, 27 Oct 2008 23:33:09 GMT

Mike, you may very well be right, as I don't work in the Linq To Sql team (I'm in the ASP.NET/Dynamic Data team), and I'm aware of everything they are doing. It might be worth asking on the Linq To Sql forum (http://forums.microsoft.com/msdn/ShowForum.aspx?siteid=1&ForumID=123) to reach the 'experts' in that area.

From a Dynamic Data point of view, if Linq To Sql adds this support we can support it accordingly in the field template.

re: A ‘Many To Many’ field template for Dynamic Data

Dave Townsend — Sun, 02 Nov 2008 03:48:28 GMT

Great Post! Thank you. Anyone attended the PDC last week?

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re: A ‘Many To Many’ field template for Dynamic Data

ryan martin — Tue, 11 Nov 2008 00:30:23 GMT

I spent 10 hours, literally trying to get this to work with my SQL Server 2008 database. I downloaded this Many To Many example and it worked perfectly fine, except I couldn’t get mine to work the same. My application wouldn't update it would just stick so I combed through all of the code in both apps to find the difference.

Well I'm embarrassed to admit I did not make the linking table (EmployeesTerritories) two ID fields (EmployeeID, TerritoryID) as primary keys and foreign keys respectfully. I tried to do this relationship connection through the entity model instead. So if anyone is having a similar issue, try this out! Build the relationships in your database first.

re: A ‘Many To Many’ field template for Dynamic Data

Quitnen Miller — Thu, 04 Dec 2008 04:51:42 GMT

Thank you for the great post on how to deal with Many-To-Many relationships. Unfortunately it doesn't work in its current form on the project I'm working on because the joining table contains some data about the relationship.

I am looking into explicititly defining the relationship as opposed to implicity having it defined.

I do have one question regarding the AutoFieldGenerator. Specifically the following lines.

string uiHint = null;

if (column.Provider.Association != null && column.Provider.Association.Direction == AssociationDirection.ManyToMany) {

uiHint = "ManyToMany";

}

fields.Add(new DynamicField() { DataField = column.Name, UIHint=uiHint });

I noticed that the UIHint is set to either null or ManyToMany yet it still seems to pick up UIHints defined in a MetadataType Class.

[UIHint("Image")]

public object Logo{ get; set; }

Is that because the UIHint from the MetadataType is applied after the AutoFieldGenerator. If that is the case, any UIHint's for the FK field will remove the ManyToMany that is applied in the AutoFieldGenerator.

I thought I should have used something like the following but found it made no difference:

UIHint = uiHint != null ? uiHint : column.UIHint

Cheers

re: A ‘Many To Many’ field template for Dynamic Data

davidebb — Thu, 04 Dec 2008 04:57:57 GMT

This works because if DynamicField has a null UIHint, then it always defaults to the one from the MetaColumn. Basically, what you set on the DynamicField overrides the MetaColumn uihint.

David

re: A ‘Many To Many’ field template for Dynamic Data

J Stroud — Wed, 17 Dec 2008 23:15:35 GMT

I'm getting a 'Repeater1 not found' type error in ManyToMany.aspx.cs when I include this in my own project...I've made the necessary mods to ensure it's in the proper namespace and everything.

Any ideas?

re: A ‘Many To Many’ field template for Dynamic Data

davidebb — Thu, 18 Dec 2008 01:15:54 GMT

J Stroud: the field templates were written for a web site. To use them in a Web Application, right click the aspx files in VS and choose 'convert to web application'. You should then be ok.

David

re: A ‘Many To Many’ field template for Dynamic Data

J Stroud — Thu, 18 Dec 2008 18:12:48 GMT

Thanks! Still muddling about with 2008.

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re: A ‘Many To Many’ field template for Dynamic Data

Michael — Sat, 20 Dec 2008 16:23:43 GMT

Does this control work for Dynamic Data LinqToSQL apps ? If not would it be possible to ?

re: A ‘Many To Many’ field template for Dynamic Data

davidebb — Mon, 22 Dec 2008 21:49:14 GMT

Michael, copying from a recent forum thread: "I think in theory it can be made to work with Linq to SQL, but it would certainly be harder. The reason is that with L2S, the framework doesn't abstract out the 'junction table', so the field templates would need to do all the book keeping themselves to make it all work. But in theory, I don't see why it couldn't be made to work with the right field template."

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re: A ‘Many To Many’ field template for Dynamic Data

philip — Tue, 06 Jan 2009 20:31:39 GMT

I tried your code, works very nice, thanks. Though, ManyToMany_Edit.ascx isn't loaded/executed when in 'Insert' mode.

When I set a breakpoint in 'Page_Load' of ManyToMany_Edit, it doesn't even get there.

Any ideas?!

philip

re: A ‘Many To Many’ field template for Dynamic Data

davidebb — Tue, 06 Jan 2009 21:31:58 GMT

Philip, what exactly are you trying? In the sample I shared, if I:

- Go to Territories/ListDetails.aspx

- Click New on the DetailView

The insert UI correctky uses the Many To Many field template to pick employee.

re: A ‘Many To Many’ field template for Dynamic Data

Jan Ehlers — Thu, 08 Jan 2009 13:18:45 GMT

I have implemented this field on a web-application, and it works. It does however result in a lot of roundtrips to the database. It seems that for every foreignkey column in every row on the main table a call to the database is made to extract the related records. This means that a page with 10 records shown and 3 many to many columns makes 30 extra calls to the database. The call is made every time a RelatedEnd entityCollection is loaded. On the listDetails page you do load foreignkeycolumns explicitly, so why is it necessary to do this row by row loading of related entities?

re: A ‘Many To Many’ field template for Dynamic Data

davidebb — Thu, 08 Jan 2009 22:24:50 GMT

Jan, this happens because by default we only Include the entity ref columns in the query, and not the entity sets. See this line in list.aspx.cs:

GridDataSource.Include = table.ForeignKeyColumnsNames;

If you were to add the ManyToMany column in that list, you should get all the data in one query. e.g. in the Territories case, with the current code the Include only gets set to "Region". Instead, you'd want to set it to "Region,Employees".

re: A ‘Many To Many’ field template for Dynamic Data

Jan Ehlers — Fri, 09 Jan 2009 12:22:01 GMT

Hi David

Thank you for the quick response. It did the trick when I put this check on the related end:

if (!entityCollection.IsLoaded)

{

entityCollection.Load();

}

It does however require that I use a custom page in order to hardcode the table names that needs to be included in the GridDataSource query. I already have this, so that is ok. For later usage however I would like to know if you know a general way to get the names of the navigation properties on the main entity to be able to include the entitities behind them. If there is such I way, I suggest this as the default behavior for the ListDetails page.

Regards, Jan

re: A ‘Many To Many’ field template for Dynamic Data

davidebb — Sat, 10 Jan 2009 04:22:08 GMT

Jan, you should be able to do this by looking at table.Columns.OfType<MetaChildrenColumn>(), and add them to the include. Obviously, this needs to be done carefully, as it will cause one big query to happen. It's good if the data ends up being used, and bad if not (e.g. if the column ends up not being displayed).

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