Primary key issue with Entity Framework

Hi,

I need to create a view that uses an old Customer table, which has a primary key that doesn't end in "ID".  The class and context are:

    public partial class CUS_Customer
    {
        public int CUS_THIS_RECORD { get; set; }

        public string CUS_Name { get; set; }

        //We just need this basic subset of the QTEC.CUS_Customer table initially
    }

and

    public class QTECContext : DbContext
    {
        public virtual DbSet<CUS_Customer> CUS_Customer { get; set; }

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            optionsBuilder.UseSqlServer(@"Not for public consumption");
        }

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.Entity<CUS_Customer>(entity =>
            {
                entity.ToTable("CUS_Customer", "dbo");

                entity.Property(e => e.CUS_Name).HasMaxLength(60);
            });
        }

    }

When I use LINQ to access this data:

        public SelectList GetCustomers()
        {
            QTECContext db = new QTECContext();

            var Customers = from d in db.CUS_Customer orderby d.CUS_Name select new { d.CUS_THIS_RECORD, d.CUS_Name };

            return new SelectList(Customers, "CUS_THIS_RECORD", "CUS_Name");
        }

I get the following error:

InvalidOperationException: The entity type 'CUS_Customer' requires a primary key to be defined....

The guidelines https://docs.microsoft.com/en-us/ef/core/modeling/keys imply that only properties/columns that end in "ID" can be primary keys.  Is this there a way of forcing the DBContext to recognise a primary key of any name?

I'm using Core version 1.1...and please no comments about instantiating DBContexts the way I have.  I have very limited time to get a demo done and I know this way works.

Kind regards, Paul