C# CRM m:n relationship

Question

In my CRM database, I have two entity groups, A and B, linked by an m:n-relationship. There are many instances of entity A each linked to several instances of entity B. For a particular entity, let's say an an instance of entity A, how do I get all the linked instances of entity B?

var service = new OrganizationService(_connection);

var retrieveRequest = new RetrieveMultipleRequest();

retrieveRequest.Query = new QueryExpression
    {
        EntityName = "new_A",
        ColumnSet = new ColumnSet(true)
    }; 

var crmReponse = (RetrieveMultipleResponse)service.Execute(retrieveRequest);

When viewing crmResponse in debugging mode, I see all instances of entity A, but I do not see anything within the RelatedInstances property. What am I doing wrong?

EDIT: After getting the first answer, I adapted my code as follows:

var linkEntities = new LinkEntity { 

    LinkFromEntityName = "new_A",
    LinkToEntityName = "new_B"

};

var retrieveRequest = new RetrieveMultipleRequest();

var query = new QueryExpression
{
    EntityName = "new_A",
    ColumnSet = new ColumnSet(true)
};

query.LinkEntities.Add(linkEntities);

retrieveRequest.Query = query;

var crmReponse = (RetrieveMultipleResponse)service.Execute(retrieveRequest);

Now I get an error, though:

No system many-to-many relationship exists between new_customer_system_machine_type and new_customer_system_machine_check. If attempting to link through a custom many-to-many relationship ensure that you provide the from and to attributes.

However, when I created that many-to-many-relationship, I did not specify any attribute names, it was merely between the entities. What am I doing wrong?

Also, my RetrieveMultipleRequest class does not have the property ReturnDynamicEntities

CRM 4, at least that's the version of the SDK. – arik Jul 13 '12 at 07:25 — arik, Jul 13 '12 at 07:25

score 1 · Answer 1 · answered Jul 13 '12 at 13:01

1

You need to specify the LinkFromAttributeName and the LinkToAttributeName. These are going to be the attributes of the from and to entities that contain the matching key values.

answered Jul 13 '12 at 13:01

Daryl

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But the many-to-many-relationship did not generate any keys for neither of the entities. Additionally, when I specify a made-up attribute name, it throws an error because that attribute name does not exist. – arik Jul 13 '12 at 13:17

score 0 · Answer 2 · answered Jul 13 '12 at 08:42

0

You can find answer in this blog post. There described two ways:
- RetrieveMultipleRequest with LinkEntity class;
- Fetch

answered Jul 13 '12 at 08:42

paramosh

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Thanks. It still does not work though, could you please read my edit? – arik Jul 13 '12 at 09:07

C# CRM m:n relationship

2 Answers2