A useful little EF extension method

EntityFrameworkExtensions.cs

using System;
using System.Data.Entity;

public static class EntityFrameworkExtensions
{
    /// <summary>
    ///     Given an id, creates a reference to an existing (persisted) *unchanged* entity
    /// </summary>
    /// <typeparam name="TEntity">Entity CLR type</typeparam>
    /// <param name="db">DbContext</param>
    /// <param name="id">Entity Id</param>
    /// <returns></returns>
    public static TEntity GetEntityReference<TEntity>(this DbContext db, Guid id) where TEntity : Entity, new()
    {
        foreach (var entity in db.ChangeTracker.Entries<TEntity>())
        {
            // the entity is already being tracked
            if (entity.Entity.Id == id)
            {
                return entity.Entity;
            }
        }

        var temp = db.Entry(new TEntity { Id = id });
        temp.State = EntityState.Unchanged;
        return temp.Entity;
    }
}

Usually use something like this as an entity base class... https://gist.github.com/mhinze/1315423