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n:m relationshi...

n:m relationships

6/8/2007 8:01:28 AM

Siclone

1 posts

n:m relationships

I have a question in relation to Relations. I apologise if my description of the problem is unclear, but here goes.

I have created a class that defines a list that holds references to objects of itself. Example:

A Profile object (based on the Profile class as defined below) is intended to hold a list of other Profiles (referred to in the code as subProfiles). A Profile can exist on its own, without any subProfiles, or it can exist as a subprofile to 1 or more other Profile objects. For example, I have 4 x Profile objects P1, P2, P3 and P4. P1, has P2 and P3 as subprofiles whilst P4 has P3 as a subprofile.

Everything with NDO seems to work as per the manual and I create the database, execute my test code which creates the 4 x Profile objects, makes them persistent and then adds them (as subProfiles) to their respective parent Profile objects. The problem that exists is that a Profile object can only be related to 1 other Profile object, Ie: P3 can only be related to P4, or P1 and not both.

I have created other n:m relationships that use a Composite relationship in the middle, but none as per my description above. Hopefully I am not doing something obviously incorrect!

The NDO created SQL code to generate the Profile table is included below.

I'd appreciate any pointers or help. cheers

BTW: The tutorial zip file on your site appears to be corrupt after downloading. FYI

/// <summary>
/// Summary for Profile\
/// </summary>

[NDOPersistent]
public class Profile
{

string name;

[NDORelation(typeof(Profile))]
ArrayList subProfiles = new ArrayList();
public IList SubProfiles
{
get { return ArrayList.ReadOnly(subProfiles); }
set { subProfiles = (ArrayList)value; }
}

public void AddProfile(Profile p)
{
subProfiles.Add(p);
}

public void RemoveProfile(Profile p)
{
if (subProfiles.Contains(p))
subProfiles.Remove(p);

}

.....

CREATE TABLE [Profile](

[ID] Int IDENTITY (1, 1) NOT NULL,

[Name] NVarChar(255) NULL,

[IDProfile] Int NULL,

CONSTRAINT [PK_Profile] PRIMARY KEY ([ID])

);