I have the following base class:

public abstract class CheckBase<TInput, TOrder, TReply> : ICheck<TInput, TOrder, TReply> where TInput : ITicker where TReply : ITicker {

  public abstract IEnumerable<TReply> Compute(IEnumerable<TOrder> orders);

  public virtual IEnumerable<TReply> Compute(IEnumerable<TInput> inputs, Func<TInput, TOrder> mapper) {

    return Compute(inputs.OrderBy(x => x.Stamp).Select(x => mapper(x)));

  }

And a derived class:

public class CheckSystem : CheckBase<ITicker, (DateTimeOffset Stamp, Decimal? Value), CheckSystem.Reply> {

  public override IEnumerable<Reply> Compute(IEnumerable<(DateTimeOffset Stamp, Decimal? Value)> orders) {

    // Just for testing 
    return new List<Reply>()
    
  } 

  public class Reply(DateTimeOffset stamp, Decimal? value) : ITicker {

    public DateTimeOffset Stamp { get; set; } = stamp;
    public Decimal? Value { get; set; } = value;
    
  } 

}

I am using it as follows:

public class SystemModel(DateTimeOffset stamp, Decimal? reference) : ITicker {
  public DateTimeOffset Stamp { get; set; } = stamp;
  public Decimal? Reference { get; set; } = reference;
}

CheckSystem checkSystem = new CheckSystem();  

IEnumerable<SystemModel> models = getModels();

var result = checkSystem.Compute(models, x => (x.Stamp, x.Reference)); 

I get an error in x.Reference because x is considered ITicker and not SystemModel.

How can I change my code so that the method

public virtual IEnumerable<TReply> Compute(IEnumerable<TInput> inputs, Func<TInput, TOrder> mapper)

“knows” the type of TInput and not only that it implements ITicker so I can access all its properties?