Entity Framework adding record into many to many mapping table

.net, c#, entity-framework, many-to-many

Solution

Flying a little blind since you didn't include what properties `entity` has. But you should have a property for the relationship to `CustomerGroups`. Just set that property with the groups you want to be related to. For example, this would create a new Group name "foo bar" and relate the entity to that group.

using (var context = DataObjectFactory.CreateContext())
{
    entity.CustomerGroups = new List<CustomerGroup> { GroupName = "Foo bar" };
    context.Customers.Add(entity);
    context.SaveChanges();
    return entity.Id;
}

If the relationship is setup correctly, EF will automatically insert a record into `CustomerGroups` and insert a relationship into the `CustomerInGroups` table.

EDIT:

If you're trying to add an existing `CustomerGroup` to a new Customer. You'll want to get the `CustomerGroup` from the database first, then add it to the Customer entity you're inserting.

using (var context = DataObjectFactory.CreateContext())
{
    var customerGroups = context.CustomerGroups.Where(...).ToList(); // get your CustomerGroup object(s) here, and ensure it's enumerated with ToList()
    entity.CustomerGroups = customerGroups;
    context.Customers.Add(entity);
    context.SaveChanges();
    return entity.Id;
}

Problem

I have 3 tables, 1) Customer (Id, Name, bla bla) 2) CustomerGroups (GroupId, GroupName) 3) CustomerInGroups (CustomerId, GroupId) ``` using (var context = DataObjectFactory.CreateContext()) { context.Customers.Add(entity); context.SaveChanges(); return entity.Id; } ``` How do I add a record into CustomerInGroups? EntityFramework doesn't generate entities for such many-to-many mapping tables Edit: Both the Id columns in Customer and CustomerGroups are set to auto increment. So in my CustomersGroup table, I have ``` Id Name ---------------------------- 1 Normal 2 VIP ``` I tried doing this as one of the posters suggested: ``` entity.CustomerGroups = new List<CustomerGroup> { new CustomerGroup {Id = 2 } }; context.Customers.Add(entity); context.SaveChanges(); return entity.Id; ``` However, when I did this, instead of creating a record in the mapping table like this: ``` CustomerId GroupId ---------------------------- 1 2 ``` What I got was ``` CustomerInGroups CustomerId GroupId ---------------------------- 1 3 CustomerGroups Id Name ---------------------------- 1 Normal 2 VIP 3 NULL ``` It actually created another entry in my CustomerGroups table, which is not what I want

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