why the property in the derived class is not accessible here?

Question

public class LoanPerformance

{

    public decimal Principal { get; set; }

}

public class AggregatedPerformance

{

    public int LoanId { get; set; }

    public decimal Principal { get; set; }

    public virtual void Aggregate<TLoanPerformance, TAggregated>(IEnumerable<TLoanPerformance> loanPerformances, Action<TLoanPerformance> accumulator)

        where TLoanPerformance : LoanPerformance

        where TAggregated : AggregatedPerformance, new()

    {

        foreach (TLoanPerformance loanPerformance in loanPerformances)

        {

            this.Principal += loanPerformance.Principal;

            accumulator(loanPerformance);

        }

    }

    public void Aggregate<TLoanPerformance, TAggregated>(IEnumerable<TLoanPerformance> loanPerformances)

        where TLoanPerformance : LoanPerformance

        where TAggregated : AggregatedPerformance, new()

    {

        Aggregate<TLoanPerformance, TAggregated>(loanPerformances, _ => { });

    }

}

public class CreditCardPerformance : LoanPerformance

{

    public decimal CreditLimit { get; set; }

}

public class CCAggregatedPerformance : AggregatedPerformance

{

    public decimal CreditLimit { get; set; }

    public override void Aggregate<CreditCardPerformance, CCAggregatedPerformance>(IEnumerable<CreditCardPerformance> loanPerformances, Action<CreditCardPerformance> accumulator)

    {

        base.Aggregate<CreditCardPerformance, CCAggregatedPerformance>(loanPerformances,

        (_perf) =>

        {

            var creditCardPerf = _perf as CreditCardPerformance;

            if (creditCardPerf != null)

            {

                this.CreditLimit += creditCardPerf.CreditLimit; // Error CS1061  'AggregatedPerformance' does not contain a definition for 'CreditLimit' and no accessible extension method 'CreditLimit' accepting a first argument of type 'AggregatedPerformance' could be found(are you missing a using directive or an assembly reference ?)

            }

        });

    }

}

Answer 1

Two things:

• Your override of Aggregate in CCAggregatedPerformance has differently named type arguments than those defined in the base class AggregatedPerformance. Not a technical issue, but denotes an assumption that the type passed can't be another derived type of LoanPerformance when it is possible with the constraints applied in the base class.
• The override of Aggregate also had a name collision between the first type argument (CreditCardPerformance) and the class CreditCardPerformance. Renaming this type argument resolves the issue.

Updated:

public class LoanPerformance {

	public decimal Principal { get; set; }

}

public class AggregatedPerformance {

	public int LoanId { get; set; }

	public decimal Principal { get; set; }

	public virtual void Aggregate<TLoanPerformance, TAggregated>(IEnumerable<TLoanPerformance> loanPerformances, Action<TLoanPerformance> accumulator)

		where TLoanPerformance : LoanPerformance

		where TAggregated : AggregatedPerformance, new() {

		foreach (TLoanPerformance loanPerformance in loanPerformances) {

			this.Principal += loanPerformance.Principal;

			accumulator(loanPerformance);

		}

	}

	public void Aggregate<TLoanPerformance, TAggregated>(IEnumerable<TLoanPerformance> loanPerformances)

		where TLoanPerformance : LoanPerformance

		where TAggregated : AggregatedPerformance, new() {

		Aggregate<TLoanPerformance, TAggregated>(loanPerformances, _ => { });

	}

}

public class CreditCardPerformance : LoanPerformance {

	public decimal CreditLimit { get; set; }

}

public class CCAggregatedPerformance : AggregatedPerformance {

	public decimal CreditLimit { get; set; }

	public override void Aggregate<TLoanPerformance, TAggregated>(IEnumerable<TLoanPerformance> loanPerformances, Action<TLoanPerformance> accumulator) {

		base.Aggregate<TLoanPerformance, CCAggregatedPerformance>(loanPerformances,

			(_perf) => {

				var creditCardPerf = _perf as CreditCardPerformance;

				if (creditCardPerf != null) {

					this.CreditLimit += creditCardPerf.CreditLimit;

				}

			});

	}

}