EntityFramework - Entity proxy error

Above solution may occur such as error "Conflicting changes to the role x of the relationship y have been detected". I achieve that error with using this method;

 public virtual TEntity DetachEntity(TEntity entityToDetach)
    {
        if (entityToDetach != null)
            context.Entry(entityToDetach).State = EntityState.Detached;
        context.SaveChanges();
        return entityToDetach;
    }

i hope it'll work for you too.

This happened to me too when I tried to implement ICloneable on my entity and cloned it using MemberwiseClone. Worked great when I was using entities that I instantiated myself. However, when I used this to clone an entity that had been loaded using EF, I got this error whenever I tried to add it to a DbSet (or in various other parts).

After some digging, I found that when you clone an EF-loaded entity, you're cloning the proxy class as well. One of the things a proxy class carries around is a reference to the wrapper fo the given entity. Because a shallow copy only copies a reference to the wrapper, you suddenly have two entities that have the same wrapper instance.

At this point, EF thinks you've created or borrowed a different proxy class for your entity which it assumes is for purposes of mischief and blocks you.

Edit

Here's a snippet that I created to work around this problem. Note that this will do a fair job of copying just the EF properties, but it's not perfect. Note that you'll need to modify it if you have private fields that must be copied as well, but you get the idea.

    /// <summary>
    /// Makes a shallow copy of an entity object. This works much like a MemberwiseClone
    /// but directly instantiates a new object and copies only properties that work with
    /// EF and don't have the NotMappedAttribute.
    /// </summary>
    /// <typeparam name="TEntity">The entity type.</typeparam>
    /// <param name="source">The source entity.</param>
    public static TEntity ShallowCopyEntity<TEntity>(TEntity source) where TEntity : class, new()
    {

        // Get properties from EF that are read/write and not marked witht he NotMappedAttribute
        var sourceProperties = typeof(TEntity)
                                .GetProperties()
                                .Where(p => p.CanRead && p.CanWrite &&
                                            p.GetCustomAttributes(typeof(System.ComponentModel.DataAnnotations.NotMappedAttribute), true).Length == 0);
        var newObj = new TEntity();

        foreach (var property in sourceProperties)
        {

            // Copy value
            property.SetValue(newObj, property.GetValue(source, null), null);

        }

        return newObj;

    }

I solved it this way.

using (var ctx = new MyContext())
      {
         ctx.Configuration.ProxyCreationEnabled = false;

         return ctx.Deferrals.AsNoTracking().Where(r => 
         r.DeferralID.Equals(deferralID)).FirstOrDefault();
      }