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Mapping Non-Public Members With Entity Framework Code First

This is a common request, and really makes sense; we need to use LINQ expressions and a bit of reflection magic. First, an helper function for returning an expression that points to a member:

   1: public static class ExpressionHelper
   2: {
   3:     public static Expression<Func<TEntity, TResult>> GetMember<TEntity, TResult>(String memberName)
   4:     {
   5:         ParameterExpression parameter = Expression.Parameter(typeof(TEntity), "p");
   6:         MemberExpression member = Expression.MakeMemberAccess(parameter, typeof(TEntity).GetMember(memberName, BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance).Single());
   7:         Expression<Func<TEntity, TResult>> expression = Expression.Lambda<Func<TEntity, TResult>>(member, parameter);
   8:         return (expression);
   9:     }
  10: }

Then, we call it on the DbContext.OnModelCreating method, as a parameter to StructuralTypeConfiguration<TStructuralType>.Property:

   1: protected override void OnModelCreating(DbModelBuilder modelBuilder)
   2: {
   3:     modelBuilder.Entity<Project>().Property(ExpressionHelper.GetMember<Project, Decimal>("Budget")).IsRequired();
   5:     base.OnModelCreating(modelBuilder);
   6: }
And that’s it!


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