The object cannot be deleted because it was not found in the ObjectStateManager

I am getting this error "The object cannot be deleted because it was not found in the ObjectStateManager."

My code is:

    protected MyEntities sqlEntities;

    public virtual void Delete(TEntity entity)
    {
        System.Type t = typeof(TEntity);
        sqlEntities.DeleteObject(entity);
        sqlEntities.SaveChanges();
    }