DataContextExtensions.cs

 public static class DataContextExtensions
 {
     /// <summary>
     /// Map private collection property
     /// </summary>
     /// <typeparam name="T">Entity type</typeparam>
     /// <typeparam name="R">Collection entity</typeparam>
     /// <param name="propertyName">property name</param>
     public static ManyNavigationPropertyConfiguration<T, R> HasMany<T, R>(this EntityTypeConfiguration<T> mapper, string propertyName)
         where T : class
         where R : class
     {

         Type type = typeof(T);
         ParameterExpression arg = Expression.Parameter(type, "x");
         Expression expr = arg;

         PropertyInfo pi = type.GetProperty(propertyName, BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Instance);
         expr = Expression.Property(expr, pi);

         LambdaExpression lambda = Expression.Lambda(expr, arg);

         var expression = (Expression<Func<T, ICollection<R>>>)lambda;

         return mapper.HasMany(expression);
     }

     /// <summary>
     /// Map private property
     /// </summary>
     /// <typeparam name="T">Entity type</typeparam>
     /// <param name="propertyName">property name</param>
     public static StringPropertyConfiguration Property<T>(this EntityTypeConfiguration<T> mapper, string propertyName) where T : class
     {
         Type type = typeof(T);
         ParameterExpression arg = Expression.Parameter(type, "x");
         Expression expr = arg;

         PropertyInfo pi = type.GetProperty(propertyName, BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Instance);
         expr = Expression.Property(expr, pi);

         LambdaExpression lambda = Expression.Lambda(expr, arg);

         var expression = (Expression<Func<T, string>>)lambda;

         return mapper.Property(expression);
     }
 }