ln.identities/BaseIdentityProvider.cs

using System;
using System.Collections.Generic;
using System.Linq;

namespace ln.identities
{
    public abstract class BaseIdentityProvider : IIdentityProvider
    {
        public BaseIdentityProvider()
        {
        }

        public virtual Identity Authenticate(AuthenticationProve authenticationProve)
        {
            Identity identity = GetIdentity(authenticationProve.IdentityName);
            if (identity == null)
                throw new KeyNotFoundException();

            SecureAttribute secureAttribute = identity.GetSecureAttribute(authenticationProve.SecureAttributeUniqueID);
            if (secureAttribute.Authenticate(authenticationProve.Challenge, authenticationProve.Prove))
            {
                return identity;
            }
            throw new ArgumentOutOfRangeException();
        }

        public abstract Identity CreateIdentity(string identityName);
        public abstract IEnumerable<KeyValuePair<Guid, string>> GetIdentities();
        public abstract Identity GetIdentity(Guid uniqueID);
        public abstract bool Save(Identity identity);

        public virtual Identity GetIdentity(string identityName) => GetIdentity(GetIdentities().FirstOrDefault((kvp) => identityName.Equals(kvp.Value)).Key);
    }
}