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Fluent Builder pattern which returns root type

I want to create builder for my purpose, with such call chain:
User user = new CommonBuilder(new UserNode()).Root //generic parameter, currently is User
.Group.Group.Folder.Build();
Here is the code, which I use:
public abstract class AbstractNode
{
public Guid Id { get; } = Guid.NewGuid();
}
public abstract class AbstractNode<T> where T : AbstractNode<T>
{
}
public class CommonBuilder<T> where T : AbstractNode<T>
{
public T Root { get; private set; }
public CommonBuilder(T root)
{
Root = root;
}
}
public class UserNode : AbstractNode<UserNode>
{
private GroupNode _group;
public GroupNode Group
{
get
{
if (_group is null)
{
_group = new GroupNode();
}
return _group;
}
}
}
public class GroupNode : AbstractNode<GroupNode>
{
private GroupNode _group;
public GroupNode Group
{
get
{
if (_group is null)
{
_group = new GroupNode();
}
return _group;
}
}
private FolderNode _folder;
public FolderNode Folder
{
get
{
if (_folder is null)
{
_folder = new FolderNode();
}
return _folder;
}
}
}
public class FolderNode : AbstractNode<FolderNode>
{
}
The problem is in the Build() method, which need to return Root from CommonBuilder, not the File.
Where must I place Build() method, which must be always called at the end of a chain, which returns Root of a builder?

In case when it's required to make a chain the same object should be returned, even as another interface check first and second examples of implementation Builder with Fluent intefaces
I've tried to implement your case to fit the role, check if it will fits your requirements:
public interface IGroup<T>
{
IGroup<T> Group { get; }
IFolder<T> Folder { get; }
}
public interface IFolder<T>
{
T Build();
}
Builder implements all required interfaces. And returns itself in each call. In general you can put Build method in the builder itself and call it separately after the end of chain execution.
public class CommonBuilder<T> : IGroup<T>, IFolder<T> where T: INode, new()
{
private T _root = new T();
public T Build()
{
return _root;
}
public IGroup<T> Group
{
get
{
_root.MoveToGroup();
return this;
}
}
public IFolder<T> Folder
{
get
{
_root.MoveToFolder();
return this;
}
}
}
Because of generics it's required to set some limitations on generic parameter which is done with INode interface
public interface INode
{
void MoveToGroup();
void MoveToFolder();
}
Testing user object
public class User : INode
{
public StringBuilder Path { get; } = new StringBuilder();
public void MoveToFolder()
{
Path.AppendLine("Folder");
}
public void MoveToGroup()
{
Path.AppendLine("Group");
}
public override string ToString()
{
return Path.ToString();
}
}
And the call will looks like
var user = new CommonBuilder<User>().Group.Group.Folder.Build();
EDIT
Maybe as a the first stage it makes sence to get rid of Fluent interfaces and implement logic using just a Builder:
public class FolderNode : INode<Folder>
{
private readonly Folder _folder = new Folder();
public Folder Build()
{
return _folder;
}
public void AppendGroup()
{
_folder.Path.AppendLine("Folder Group");
}
public void AppendFolder()
{
_folder.Path.AppendLine("Folder Folder");
}
}
public class UserNode : INode<User>
{
private readonly User _user = new User();
public User Build()
{
return _user;
}
public void AppendGroup()
{
_user.Path.AppendLine("Group");
}
public void AppendFolder()
{
_user.Path.AppendLine("Folder");
}
}
public class CommonBuilder<T, TNode> where TNode : INode<T>
{
private readonly TNode _root;
public CommonBuilder(TNode root)
{
_root = root;
}
public T Build()
{
return _root.Build();
}
public CommonBuilder<T, TNode> Group {
get
{
_root.AppendGroup();
return this;
}
}
public CommonBuilder<T, TNode> Folder {
get
{
_root.AppendFolder();
return this;
}
}
}
public interface INode<out T>
{
T Build();
void AppendGroup();
void AppendFolder();
}
public class Folder
{
public StringBuilder Path { get; } = new StringBuilder();
public override string ToString()
{
return Path.ToString();
}
}
public class User
{
public StringBuilder Path { get; } = new StringBuilder();
public override string ToString()
{
return Path.ToString();
}
}
Usage:
var user = new CommonBuilder<User, UserNode>(new UserNode()).Group.Group.Folder.Build();
var folder = new CommonBuilder<Folder, FolderNode>(new FolderNode()).Group.Folder.Group.Folder.Build();

Inheritance in nested classes C#

fans of beautiful code.
I would like to ask my question by two ways. May be it will be useful to understand me.
1) There is code of 2 classes. One of them is nested. Nested class is used to get access to private fields of other one. I would like to get inherit class B:A{class BUnit:AUnit{}} which has the same functional but else has some more methods and fields in B and BUnits classes. How it can be done?
class Program
{
static void Main(string[] args)
{
A a = new A();
a.Add();
a.Add();
a.Add();
bool res=a[0].Rename("1");//res=true;
res = a[1].Rename("1");//res= false;
Console.ReadKey();
}
}
class A
{
private List<AUnit> AUnits;
public AUnit this[int index] {get {return AUnits[index];}}
public A()//ctor
{
AUnits = new List<AUnit>();
}
public void Add()
{
this.AUnits.Add(new AUnit(this));
}
public class AUnit
{
private string NamePr;
private A Container;
public AUnit(A container)//ctor
{
NamePr = "Default";
this.Container = container;
}
public string Name { get { return this.NamePr; } }
public Boolean Rename(String newName)
{
Boolean res = true;
foreach (AUnit unt in this.Container.AUnits)
{
if (unt.Name == newName) res = false;
}
if (res) this.NamePr = String.Copy(newName);
return res;
}
}
}
2) There is two very similar “things” – Class A and Class B. Is it possible to separate their common part, and then “inherit” this two “things” from it ? For example, I would like add some methods like GetUnitsCount() or RemoveUnit() and this methods are common for both. So I should “CopyPaste” this method to A and B but it is not good idea. It will be better to change their common part one time in one place. There is no important how it can be done – inheriting or interfaces or anything else. Important - how?
class Program
{
static void Main(string[] args)
{
A a = new A();
a.Add();
a[0].objB.Add();
a[0].objB.Add();
a[0].objB[0].Val1 = 1;
int res = a[0].objB[0].Val1 + a[0].objB[0].Val2;
Console.ReadKey();
}
}
class A
{
private List<AUnit> Units;
public AUnit this[int index] {get {return Units[index];}}
public A()//ctor
{
Units = new List<AUnit>();
}
public void Add()
{
this.Units.Add(new AUnit(this));
}
public class AUnit
{
private string NamePr;
private A Container;
public B objB;
public AUnit(A container)//ctor
{
NamePr = "Default";
this.Container = container;
this.objB = new B();
}
public string Name { get { return this.NamePr; } }
public Boolean Rename(String newName)
{
Boolean res = true;
foreach (AUnit unt in this.Container.Units)
{
if (unt.Name == newName) res = false;
}
if (res) this.NamePr = String.Copy(newName);
return res;
}
}
}
class B
{
private List<BUnit> Units;
public BUnit this[int index] { get { return Units[index]; } }
public B()//ctor
{
Units = new List<BUnit>();
}
public void Add()
{
this.Units.Add(new BUnit(this));
}
public class BUnit
{
private string NamePr;
private B Container;
public int Val1{get;set;}
public int Val2{get;set;}
public BUnit(B container)//ctor
{
NamePr = "Default";
this.Container = container;
this.Val1 = 10;
this.Val2 = 17;
}
public string Name { get { return this.NamePr; } }
public Boolean Rename(String newName)
{
Boolean res = true;
foreach (BUnit unt in this.Container.Units)
{
if (unt.Name == newName) res = false;
}
if (res) this.NamePr = String.Copy(newName);
return res;
}
}
}
Thank you for your attentions.

To answer your first question, the only thing you need to to to have BUnit inherit from AUnit is to qualify AUnit:
public class BUnit : A.AUnit
{
....
}
from there I believe your question is about basic inheritance which works no differently for nested classes. Nested classes are purely for organization - they are not inherited when you inherit the "containing" class.

Making Validation Generic

I have the following C# code. Here the validations are kept outside the class to satisfy Open – Closed Principle. This is working fine. But the challenge is – the validations are not generic. It is specific to employee class (E.g DateOfBirthRuleForEmployee). How do I make the validations generic for all objects (DateOfBirthRuleForAnyObject).
Note: Make Generic <==> Make Type-Independent
Note: I have NameLengthRuleForEmployee validation also. New validation may come in future.
EDIT
Generic Method Example: Using “OfType” in LINQ
CODE
class Program
{
static void Main(string[] args)
{
Employee employee = new Employee();
employee.DateOfBirth = DateTime.Now;
employee.Name = "Lijo";
DateOfBirthRuleForEmployee dobRule = new
DateOfBirthRuleForEmployee();
NameLengthRuleForEmployee nameRule = new
NameLengthRuleForEmployee();
EmployeeManager employeeManager = new EmployeeManager();
employeeManager.AddRules(dobRule);
employeeManager.AddRules(nameRule);
bool result = employeeManager.validateEntity(employee);
Console.WriteLine(result);
Console.ReadLine();
}
}
public interface IEntity
{
}
public interface IRule<TEntity>
{
bool IsValid(TEntity entity);
}
public class DateOfBirthRuleForEmployee : IRule<Employee>
{
public bool IsValid(Employee entity)
{
return (entity.DateOfBirth.Year <= 1975);
}
}
public class NameLengthRuleForEmployee : IRule<Employee>
{
public bool IsValid(Employee employee)
{
return (employee.Name.Length < 5);
}
}
public class Employee : IEntity
{
private DateTime dateOfBirth;
private string name;
public DateTime DateOfBirth
{
get
{
return dateOfBirth;
}
set
{
dateOfBirth = value;
}
}
public string Name
{
get
{
return name;
}
set
{
name = value;
}
}
}
public class EmployeeManager
{
RulesEngine<Employee> engine = new RulesEngine<Employee>();
public void AddRules(IRule<Employee> rule)
{
engine.AddRules(rule);
//engine.AddRules(new NameLengthRuleForEmployee());
}
public bool validateEntity(Employee employee)
{
List<IRule<Employee>> rulesList = engine.GetRulesList();
//No need for type checking. Overcame Invariance problem
bool status = true;
foreach (IRule<Employee> theRule in rulesList)
{
if (!theRule.IsValid(employee))
{
status = false;
break;
}
}
return status;
}
}
public class RulesEngine<TEntity> where TEntity : IEntity
{
private List<IRule<TEntity>> ruleList = new
List<IRule<TEntity>>();
public void AddRules(IRule<TEntity> rule)
{
//invariance is the key term
ruleList.Add(rule);
}
public List<IRule<TEntity>> GetRulesList()
{
return ruleList;
}
}

The challange is for your rules to know which property of what type to validate. You can either provide this by implementing an interface that provides just that as suggested by SLaks or by quessing it dynamically or by providing a concrete rule class with a bit more information on how to access the given property, e.g.:
class NameRule<T> : IRule<T>
{
private Func<T, string> _nameAccessor;
public NameRule(Func<T, string> nameAccessor)
{
_nameAccessor = nameAccessor;
}
public bool IsValid(T instance)
{
return _nameAccessor(instance).Length > 10;
}
}
this ofcourse can be used in the following way:
NameRule<Employee> employeeNameRule = new NameRule<Employee>(x => x.name);
employeeManager.addRule(employeeNameRule);

NHibernate and State Pattern persistance - a good implementation?

Below is my implementation of the state pattern. In order to persist the State object to my database with NHibernate, I am assigning each state class an enum value. This is stored as a private field on the entity, and mapped to a integer field in my database table.
I want to know whether this is a good implementation as I will be using the state pattern throughout my application and want to get it right the first time. Thanks
public class Order
{
private OrderStatusEnum _statusId;
public virtual Guid Id { get; set; }
private OrderState _status;
public virtual OrderState Status {
get
{
if (_status == null)
_status = GetState(_statusId);
return _status;
}
set
{
_status = value;
_statusId = _status.Id;
}
}
private OrderState GetState(OrderStatusEnum status)
{
switch (_statusId) {
case OrderStatusEnum.Pending:
return new Submitted(this);
case OrderStatusEnum.Completed:
return new Completed(this);
default:
return new NewOrder(this);
}
}
}
public abstract class OrderState
{
private readonly Order _order;
public OrderState(Order order) {
_order = order;
}
internal Order Order { get { return _order; } }
public abstract OrderStatusEnum Id { get; }
public virtual void Submit() {
throw new InvalidOperationException(
string.Format("Can't Submit a {0} Order", this.GetType().Name)
);
}
public virtual void Complete() {
throw new InvalidOperationException(
string.Format(string.Format("Can't Cancel a {0} Order", this.GetType().Name))
);
}
protected internal void _Submit() {
Order.Status = new Submitted(Order);
}
protected internal void _Complete() {
Order.Status = new Completed(Order);
}
}
public class NewOrder : OrderState
{
public NewOrder(Order order) : base(order) { }
public override OrderStatusEnum Id {
get { return OrderStatusEnum.New; }
}
public override void Submit() {
_Submit();
}
}
public class Submitted : OrderState
{
public Submitted(Order order) : base(order) { }
public override OrderStatusEnum Id {
get { return OrderStatusEnum.Pending; }
}
public override void Complete() {
_Complete();
}
}
public class Completed : OrderState
{
public Completed(Order order) : base(order) { }
public override OrderStatusEnum Id {
get { return OrderStatusEnum.Completed; }
}
}
public enum OrderStatusEnum {
New = 1,
Pending = 2,
Completed = 3
}

Not sure whether to answer or add a comment, but your approach worked very well for me in a similar situation.
I also experimented with the approach described here using the Tarantino framework, but I found it easier to extend from your code.

Comparing 2 NHibernate loaded object problem

I have a class Client like that:
public class Client
{
public Person Pers { get; set; }
}
And I have 2 Person´s child class :
public class PersonType1 : Person {...}
public class PersonType2 : Person {...}
So, my Client could be PersonType1 or PersonType2...
I load 2 Client using NHibernate... And after that, I´m trying to compare than (the difference are on PersonType1 and PersonType2 attributes)...
I tried that:
public class ClientComparer : IComparer<Client>
{
public int Compare(Client __c1, Client __c2)
{
string _name1 = __c1.Person.GetType().Equals(typeof(PersonType2)) ? ((PersonType2)(__c1.Person)).Type2Att : ((PersonType1)(__c1.Person)).Type1Att ;
string _name2 = __c2.Person.GetType().Equals(typeof(PersonType2)) ? ((PersonType2)(__c2.Person)).Type2Att : ((PersonType1)(__c2.Person)).Type1Att;
if (_name1 == null)
{
if (_name2 == null)
{
return 0;
}
return -1;
}
if (_name2 == null)
{
return 1;
}
return _name1.CompareTo(_name2);
}
}
The problem is that __c1.Person.GetType() returs PersonProxy127b2a2f44f446089b336892a673643b instead of the correct type... It´s because of NHibernate...
How can I do that ? Ideas?
Thanks

Rather than having two different attributes on PersonType1 and PersonType2, define a single property in the base class Person and override it in each of the child classes. Using polymorphic behavior rather than explicit type-checking is better in any case, and essential when you're using NHibernate's proxied classes. Something like this might accomplish what you want:
public class Person
{
public string Name {get;}
}
public class PersonType2 : Person
{
private string something;
public override string Name
{
get
{
return something;
}
set
{
something = value;
}
}
}
public class PersonType2 : Person
{
private string somethingElse;
public override string Name
{
get
{
return somethingElse;
}
set
{
somethingElse = value;
}
}
}
public class Client
{
public int Compare(Client __c1, Client __c2)
{
return __c1.Pers.Name.CompareTo(__c2.Pers.Name);
}
}

Use the is operator instead of GetType():
public class ClientComparer : IComparer<Client>
{
public int Compare(Client __c1, Client __c2)
{
string _name1 = GetName(__c1.Person);
string _name2 = GetName(__c2.Person);
if (_name1 == null)
{
if (_name2 == null)
{
return 0;
}
return -1;
}
if (_name2 == null)
{
return 1;
}
return _name1.CompareTo(_name2);
}
private string GetName(Person person)
{
if (person is Person1)
{
return ((Person1)person).Type1Att;
}
else if (person is Person2)
{
return ((Person2)person).Type2Att;
}
else
{
throw new ArgumentException("Unhandled Person type.");
}
}
}