Question

I have something like this:

public void Delete(T entity)
        {
            Context.DeleteObject(entity);
            Context.SaveChanges();
        }

I end up wit a exception:
“The object cannot be deleted because it was not found in the ObjectStateManager.”
If I try to add the entity to objectContext with AttachTo() I get:

“An object with the same key already exists in the ObjectStateManager. The ObjectStateManager cannot track multiple objects with the same key.”

Whats wrong?

Example:

namespace CAFM.Data.Repository
{
    public abstract class RepositoryBase<T> : IRepository<T>
        where T : EntityObject
    {
        public RepositoryBase()
            : this(new CAFMRepositoryContext())
        {
        }
        static RepositoryBase()
        {
        }
        public RepositoryBase(IRepositoryContext repositoryContext)
        {
            _context = repositoryContext ?? new CAFMRepositoryContext();
            _entity = _repositoryContext.ObjectContext.CreateObjectSet<T>();
        }
        private readonly ObjectContext _context;
        private readonly ObjectSet<T> _entity;
        protected ObjectContext Context
        {
            get { return _context; }
        }
        protected IObjectSet<T> Entity
        {
            get { return _entity; }
        }



        #region IRepository Members

        private string GetEntityName()
        {
            return string.Format("{0}.{1}", _entity.EntitySet.EntityContainer, _entity.EntitySet.Name);
        }
        public T Add(T entity)
        {
            var fqen = GetEntityName();
            Context.AddObject(fqen, entity);
            Context.SaveChanges(SaveOptions.AcceptAllChangesAfterSave);
            return entity;
        }
        public T Update(T entity)
        {
            Context.ApplyCurrentValues(GetEntityName(), entity);
            Context.SaveChanges(SaveOptions.AcceptAllChangesAfterSave);
            return entity;
        }
        public void Delete(T entity)
        {
            Context.DeleteObject(entity);
            Context.SaveChanges();
        }
        #endregion
    }
}

Answer 1

You have to fetch the entity you wish to delete from your context first. Best to do this with a comparison of the primary key. It could look like this, but i do not know the object structure of TabMaster and TabMasterViewModel, so the properties may be wrong named.

public void Delete(TabMasterViewModel entity) { 
    TabMaster des = _tabmasterRepository.FirstOrDefault( e.Id = entity.ID );
    if (des != null) {
        _tabmasterRepository.Delete(des); 
    }
} 

You have created a new Entity and mapped the values from your view model to that entity. But the context does not know of the entity, so he could not delete it.