The ObjectStateManager does not contain an ObjectStateEntry with a reference to an object of type XXXX about entityframework-extensions HOT 6 CLOSED

public partial class Product2
{
	public Product2()
	{
		this.ActivityHistories = new HashSet<ActivityHistory>();
		this.Assets = new HashSet<Asset>();
		this.AttachedContentDocuments = new HashSet<AttachedContentDocument>();
		this.Attachments = new HashSet<Attachment>();
		this.CombinedAttachments = new HashSet<CombinedAttachment>();
		this.ContentDocumentLinks = new HashSet<ContentDocumentLink>();
		this.ContentVersions = new HashSet<ContentVersion>();
		this.EmailMessages = new HashSet<EmailMessage>();
		this.EntitySubscriptions = new HashSet<EntitySubscription>();
		this.Events = new HashSet<Event>();
		this.FeedItems = new HashSet<FeedItem>();
		this.LookedUpFromActivities = new HashSet<LookedUpFromActivity>();
		this.Notes = new HashSet<Note>();
		this.NoteAndAttachments = new HashSet<NoteAndAttachment>();
		this.OpenActivities = new HashSet<OpenActivity>();
		this.OpportunityLineItems = new HashSet<OpportunityLineItem>();
		this.PricebookEntries = new HashSet<PricebookEntry>();
		this.ProcessInstances = new HashSet<ProcessInstance>();
		this.ProcessInstanceHistories = new HashSet<ProcessInstanceHistory>();
		this.Product2Feed = new HashSet<Product2Feed>();
		this.Product2History = new HashSet<Product2History>();
		this.Tasks = new HashSet<Task>();
	}

	public string Id { get; set; }
	public string Name { get; set; }
	public string ProductCode { get; set; }
	public string Description { get; set; }
	public bool IsActive { get; set; }
	public System.DateTime CreatedDate { get; set; }
	public string CreatedById { get; set; }
	public System.DateTime LastModifiedDate { get; set; }
	public string LastModifiedById { get; set; }
	public System.DateTime SystemModstamp { get; set; }
	public string Family { get; set; }
	public bool IsDeleted { get; set; }
	public Nullable<System.DateTime> LastViewedDate { get; set; }
	public Nullable<System.DateTime> LastReferencedDate { get; set; }

	public virtual ICollection<ActivityHistory> ActivityHistories { get; set; }
	public virtual ICollection<Asset> Assets { get; set; }
	public virtual ICollection<AttachedContentDocument> AttachedContentDocuments { get; set; }
	public virtual ICollection<Attachment> Attachments { get; set; }
	public virtual ICollection<CombinedAttachment> CombinedAttachments { get; set; }
	public virtual ICollection<ContentDocumentLink> ContentDocumentLinks { get; set; }
	public virtual ICollection<ContentVersion> ContentVersions { get; set; }
	public virtual ICollection<EmailMessage> EmailMessages { get; set; }
	public virtual ICollection<EntitySubscription> EntitySubscriptions { get; set; }
	public virtual ICollection<Event> Events { get; set; }
	public virtual ICollection<FeedItem> FeedItems { get; set; }
	public virtual ICollection<LookedUpFromActivity> LookedUpFromActivities { get; set; }
	public virtual ICollection<Note> Notes { get; set; }
	public virtual ICollection<NoteAndAttachment> NoteAndAttachments { get; set; }
	public virtual ICollection<OpenActivity> OpenActivities { get; set; }
	public virtual ICollection<OpportunityLineItem> OpportunityLineItems { get; set; }
	public virtual ICollection<PricebookEntry> PricebookEntries { get; set; }
	public virtual ICollection<ProcessInstance> ProcessInstances { get; set; }
	public virtual ICollection<ProcessInstanceHistory> ProcessInstanceHistories { get; set; }
	public virtual User User { get; set; }
	public virtual User User1 { get; set; }
	public virtual ICollection<Product2Feed> Product2Feed { get; set; }
	public virtual ICollection<Product2History> Product2History { get; set; }
	public virtual ICollection<Task> Tasks { get; set; }
}

static void FetchAndSaveAllRecords<T>(DbSet<T> sourceEntity, DbContext source, DbSet<T> destinationEntity, DbContext destination) where T : class
{
	var productList = new List<Product2>();
	var productsQuery = sourceEntity.AsNoTracking().ToList();
	productsQuery.ForEach(p => productList.Add((Product2)p.CloneObject<Product2>()));
	destination.BulkInsert(productList);
	destination.BulkSaveChanges();
}

static class ObjectExtension
{
	public static object CloneObject<T>(this object objSource) where T : new()
	{
		//Get the type of source object and create a new instance of that type
		//Type typeSource = typeof(T);
		object objTarget = new T(); // Activator.CreateInstance(typeSource);
		//Get all the properties of source object type
		PropertyInfo[] propertyInfo = typeof(T).GetProperties(BindingFlags.Public | BindingFlags.NonPublic); // | BindingFlags.NonPublic | BindingFlags.Instance);
		//Assign all source property to taget object 's properties
		foreach (PropertyInfo property in propertyInfo)
		{
			//Check whether property can be written to
			if (property.CanWrite)
			{
				//check whether property type is value type, enum or string type
				if (property.PropertyType.IsValueType || property.PropertyType.IsEnum || property.PropertyType.Equals(typeof(System.String)))
				{
					property.SetValue(objTarget, property.GetValue(objSource, null), null);
				}
				//else property type is object/complex types, so need to recursively call this method until the end of the tree is reached
				else
				{
					//object objPropertyValue = property.GetValue(objSource, null);
					//if (objPropertyValue == null)
					//{
					//    property.SetValue(objTarget, null, null);
					//}
					//else
					//{
					//    property.SetValue(objTarget, objPropertyValue.CloneObject(), null);
					//}
				}
			}
		}
		return objTarget;
	}
}

destination.AddRange(productList);
destination.BulkSaveChanges();