Is an internal AND protected member possible in C#? [duplicate]

Question

Consider the following classes:

public class Vehicle { ... }
public class Coverage { ... }

public class VehicleList : IEnumerable<Vehicle> { ... }
public class CoverageList : IEnumerable<Coverage> { ... }

public abstract class Quote
{
    protected VehicleList vehicles;
    protected CoverageList coverages;

    internal Quote() { ... }

    public IReadOnlyCollection<Vehicle> Vehicles
    {
        get { return this.vehicles.AsReadOnly(); }
    }
    public IReadOnlyCollection<Coverage> Coverages
    {
        get { return this.coverages.AsReadOnly(); }
    }

    ...
}

public sealed class OhQuote : Quote
{
    //needs to access protected fields
    ...
}
public sealed class InQuote : Quote { ... }
public sealed class MiQuote : Quote { ... }

Quote fully encapsulates the functionality of both VehicleList and CoverageList so I'd like to mark those classes as internal. The problem is that they are the types of protected fields of a public class. If I mark those fields as protected internal then they are protected OR internal. What I really need is for them to be protected AND internal (with protected taking precedence within the assembly). You can see that neither Quote (which has an internal constructor) nor its subclasses (which are sealed) can be extended outside the assembly. I've already figured out how to achieve the desired functionality using public interfaces but wanted to make sure there's not a more concise way.

Answer 1

Although the .NET runtime supports this concept ("FamilyAndAssembly"), C# currently does not.

This was proposed for C# 6.0 in the form of the private protected access modifier, but the feature was dropped.

UPDATE: private protected was added to C# 7.2.