Question

This problem is similar to my previously asked question. When I query data using the Entity Framework (EF) I always use the MergeOption.NoTracking option because I end up taking my EF generated objects and mapping them to view models which have lovely attributes decorated on the property to enforce validation and so on.

I am trying to add a foreign key relationship using the EF, but anytime I do I am getting the following exception:

The object being attached to the source object is not attached to the same ObjectContext as the source object

Here is my code:

    public static void UpdateDownloadFileVersion(DownloadFile downloadFile, int[] selectedVersions) {
        using (SupportEntity supportContext = new SupportEntity()) {
            supportContext.DownloadFiles.Attach(downloadFile);

            var productVersionIdsToAdd = (from v in selectedVersions
                                          where (downloadFile.ProductVersions.Any(pv => pv.Id == v) == false)
                                          select v).ToList();

            foreach (var productVersionId in productVersionIdsToAdd) {
                var productVersion = new ProductVersion() { Id = productVersionId };
                downloadFile.ProductVersions.Attach(productVersion); //Exception happens here.
                downloadFile.ProductVersions.Add(productVersion);
            }

            supportContext.SaveChanges();
        }
    }

Answer 1

This is where Stub Entities become very very useful…

var productVersion = new ProductVersion() { Id = productVersionId };  
supportContext.AttachTo("ProductVersions", productVersion); 

Here is a good article

In above case, when attached productVersion is assigned to product versions‘ entity, productversion entity gets attached to context, with EntityState=Added. Entire graph will be in or out of context.