Having the following object(s):
public class Employee
{
public string LastName { get; set; } = "";
internal class SubordinateList<T> : List<T>, IPublicList<T> where T : Employee
{
public new void Add(T Subordinate) { }
}
public IPublicList<Employee> Subordinates = new SubordinateList<Employee>();
}
The SubordinateList object is inside the Employee object making Employee the parent of SubordinateList in a certain way.
If we put this code below:
Anakin = New Employee();
Luke = New Employee();
Anakin.Subordinates.Add(Luke);
The third line will trigger the method “Add” of SubordinateList.
I would like to get the Current Instance for the Parent of SubordinateList like this:
public new void Add(T Subordinate)
{
T Manager = Subordinate.ParentInstance;
// then it will be possible to see the current value of
// the property "LastName" for Anakin with "Manager.LastName"
}
You can't do it that way since you don't have a reference to the manager. This is how I would implement it:
public class Employee
{
public string FirstName { get; set; } = "";
public string LastName { get; set; } = "";
public string HiredDate { get; set; } = "";
private List<Employee> _subordinates = new List<Employee>();
public ReadOnlyCollection<Employee> Subordinates => _subordinates.AsReadOnly();
public void AddSubordinate(Employee employee)
{
_subordinates.Add(Employee);
//the manager is 'this'
var managerLastName = this.LastName;
}
}
Exposing the subordinate list as a ReadOnlyCollection allows other classes to read the list, but prevents them from updating the list directly. So only the AddSubordinate() method can be used to add employees, where you can do what you need with the manager's information.
Related
I'm new to both C# and MongoDB. I'm trying to add a new object to a list in a MongoDB collection, here is my code:
ProjectModel:
class ProjectModel
{
[BsonId]
public Guid Id { get; set; }
public string ProjectNumber { get; set; }
public string ProjectName { get; set; }
public PartModel[] Parts { get; set; }
}
PartModel:
class PartModel
{
public string PartNumber { get; set; }
public string PartName { get; set; }
}
Method Class
class MongoCRUD
{
private IMongoDatabase db;
public MongoCRUD(string database)
{
var client = new MongoClient();
db = client.GetDatabase(database);
}
public void InsertPart<T>(string table, Guid id, PartModel newPart)
{
var collection = db.GetCollection<T>(table);
var filter = Builders<T>.Filter.Eq("Id", id);
var update = Builders<ProjectModel>.Update.Push<PartModel>(e => e.Parts, newPart);
}
}
Main Class:
class Program
{
static void Main(string[] args)
{
MongoCRUD db = new MongoCRUD("PartsManagerDB");
PartModel newPart = new PartModel()
{
PartName = "Lower Bracket",
PartNumber = "4000"
};
db.InsertPart<PartModel>("Projects", new Guid("f3784ba4-c422-43e0-80fd-41bb87b20f10"), newPart);
}
}
The project 93100 is already in my db, but after executing my code, no error comes up but the collection is not being updated as you can see below:
You are missing the line that actually executes the two things you already have, filter and update.
public void InsertPart<T>(string table, Guid id, PartModel newPart)
{
var collection = db.GetCollection<T>(table);
var filter = Builders<T>.Filter.Eq("Id", id);
var update = Builders<ProjectModel>.Update.Push<PartModel>(e => e.Parts, newPart);
// This line will actually update your DB with the new value.
collection.FindOneAndUpdate<T>(filter, update);
}
Documentation on FindOneAndUpdate() method.
Also, in your Main() method, you need to use the class, ProjectModel instead of PartModel when calling the InsertPart method.
db.InsertPart<**ProjectModel**>("Projects", new Guid("f3784ba4-c422-43e0-80fd-41bb87b20f10"), newPart);
In the InsertPart method, T is used in your filter's Builder and it should be ProjectModel to get the Project that you are updating... not Part. Part is being inserted to the ProjectModel's PartModel array so the T should be ProjectModel.
When joining multiple models, I can't access its properties in controller.
public class BirdModel
{
public IEnumerable<BirdFile> BirdFils { get; set; }
public IEnumerable<BirdFileDetail> BirdFileDetails { get; set; }
}
public partial class BirdFile
{
public int ID{ get; set; }
public string Name{ get; set; }
}
Is it possible to access like this
BirdModel b = new BirdModel();
b.BirdFile.ID
You problem with b.BirdFile.ID is that you are trying to access the property or a collection of objects that you have not initialised.
You need to create an instance of the encapsulating class, BirdModel then create an instance of your BirdFile collection and add values to it. From there you can get the specific "BirdFile" within your collection via iteration and then access its properties.
A small example below:
class Program
{
static void Main(string[] args)
{
var bm = new BirdModel();
bm.BirdFils = new List<BirdFile>
{
new BirdFile {ID = 1, Name = "Bird A"},
new BirdFile {ID = 2, Name = "Bird B"}
};
bm.BirdFils.ToList().ForEach(x => Console.WriteLine($"Name: {x.Name}, ID: {x.ID}"));
Console.ReadKey();
}
}
public class BirdModel
{
public IEnumerable<BirdFile> BirdFils { get; set; }
}
public partial class BirdFile
{
public int ID { get; set; }
public string Name { get; set; }
}
BirdModel contains a collection of BirdFile, so to access them you should write something like:
// create a new model
BirdModel b = new BirtdModel()
// create the instance of BirdFile list
b.BirdFils = new List<BirdFile>()
// add an item (just an example)
b.BirdFils.Add(new BirdFile{ ID = 1, Name = "Bird1"}
// Access to the previously created BirdFile
BirdFile bf = b.BirdFils[0]
I have four classes :
public class Customer
{
public string FirstName { get; set; }
public string LastName { get; set; }
public List<Product> Product { get; set; }
}
public class Product
{
public int ProductNumber { get; set; }
public string ProductColor { get; set; }
}
///////////////////////////////////////////////
public class Customer_
{
public string FirstName { get; set; }
public string LastName { get; set; }
public List<Article> Article { get; set; }
}
public class Article
{
public int ArticleNumber { get; set; }
public string ArticleColor { get; set; }
}
And one instance :
var Cus = new List<Customer>
{
new Customer()
{
FirstName = "FirstName1",
LastName = "LastName1",
Product = new List<Product>
{
new Product()
{
ProductColor = "ProductColor1",
ProductNumber = 11
}
}
},
new Customer()
{
FirstName = "FirstName2",
LastName = "LastName2",
Product = new List<Product>
{
new Product()
{
ProductColor = "ProductColor2",
ProductNumber = 12
}
}
}
};
I want to create a new object List<Customer_> with the value of my instance Cus. For example Customer.FirstName = Customer_.FirstName, Customer.Product.ProductColor = Customer_.Article.ArticleColor etc
What is the best way to do this easily, could one use a Dictionary?
Mapping can be accomplished through the use of an Interface.
Define an interface(s) which provide a mapping of logically named properties such as the common color properties you mention:
// Some entities have different named properties but can be joined
// using those properties. This interface shows a common color which
// when implemented will route the processing to a common shared property
// which reports and sets the associated color.
public interface IDefinedColor
{
string Color { get; set; }
}
If you have to create partial classes for Product and Article and have them adhere to said interfaces. Hint if using an entity mapper such as EF this is a great way to do such maping using partials. Implement implement the interface and hook up the commonality:
// Holds the common properties for future processing.
public partial class Product : IDefinedColor
{
public string Color
{
get { return ProductColor; }
set { ProductColor = value; }
}
}
Then work off of the IDefinedColor mapped implementations as needed.
By using interfaces one is letting all future developers know of the contract which specifies a business logic equality in the properties and it is not hidden in other joining classes.
You could create a mapper extension class
public static class MapperExtension
{
public Customer_ Convert(this Customer customer)
{
return new Customer_()
{
FirstName = customer.FirstName,
LastName = customer.LastName,
Article = customer.Product.Convert()
};
}
public static List<Article> Convert(this List<Product> products)
{
return products.Select(x=> new Article(){
ArticleNumber = x.ProductNumber,
ArticleColor = x.ProductColor
};
}
}
make sure you reference the proper namespace where you place the extension class.
Call the code like this
Where customers is a List filled from your code
List<Customer_> convertedCustomers_ = customers.Select(x=> x.Convert()).ToList();
It depends on the relationhip between those components but I would simply add constructor to Customer_ that accepts a Customer object. And then you invoke that do perform the conversion. e.g.
public class Article
{
public Article(Product source)
{
this.ArticleNumber = source.ProductNumber;
this.ArticleColor = source.ProductColor;
}
}
public class Customer_
{
public Customer_(Customer source)
{
this.FirstName = source.FirstName;
this.LastName = source.LastName;
this.Article = source.Product.Select(o => new Article(o)).ToList()
}
...
}
//and finally to convert the list you can do something like
//initial list
var Cus = new List<Customer>() { ... etc. }
/converted list
var Cus_ = Cus.Select(o => new Cusomter_(o)).ToList();
Edit: I see from your comment above that you actually have 100 properties to map. I can see this is a pain. But if you have complex transformations like Product to Article then I would still go the manual route as above so you can be completely clear about what is going on. Alternatively you could look to use inheritance to redesign your objects with common base classes or interfaces, that would probably make mapping easier.
I'm using EF4.1 for the first time (so be patient with me) but I just cant get to grips with how I can add new items to a sub collection of an object and then save the object.
For example, with the classes below, I can initially save the TravelTicket (containing multiple People) into my database, but as soon as I add a new person and then try to save the TravelTicket again I get:
An object with the same key already exists in the ObjectStateManager. The ObjectStateManager cannot track multiple objects with the same key.
Can anyone help?
public class TravelTicket
{
public int Id { get; set; }
public string Destination { get; set; }
public virtual List<Person> Members { get; set; }
}
public class Person
{
public int Id { get; set; }
public string Name{ get; set; }
}
EDITED: All relevant code added as requested:
Domain Models:
public class TravelTicket
{
public int Id { get; set; }
public string Destination { get; set; }
public virtual ICollection<Person> Members { get; set; }
}
public class Person
{
public int Id { get; set; }
public string Name { get; set; }
}
The DB Context:
public class TicketContext : DbContext
{
public TicketContext()
: base("TicketStore")
{ }
public DbSet<TravelTicket> TravelTickets { get; set; }
public DbSet<Person> People { get; set; }
}
The Repository (relevant methods only):
public class TicketRepository : ITicketRepository
{
TicketContext context = new TicketContext();
public void InsertOrUpdate(TravelTicket quoteContainer)
{
if (quoteContainer.Id == default(int))
{
// New entity
context.TravelTickets.Add(quoteContainer);
}
else
{
// Existing entity
context.Entry(quoteContainer).State = EntityState.Modified;
}
}
public void Save()
{
try
{
context.SaveChanges();
}
catch (DbEntityValidationException dbEx)
{
foreach (var validationErrors in dbEx.EntityValidationErrors)
{
foreach (var validationError in validationErrors.ValidationErrors)
{
Trace.TraceInformation("Property: {0} Error: {1}", validationError.PropertyName, validationError.ErrorMessage);
}
}
}
}
}
public interface ITicketRepository
{
void InsertOrUpdate(TravelTicket travelTicket);
void Save();
}
The consuming (example) MVC Controller code:
public class TicketSaleController : Controller
{
private readonly ITicketRepository ticketRepository;
public TicketSaleController()
: this(new TicketRepository())
{
}
public TicketSaleController(ITicketRepository ticketRepository)
{
this.ticketRepository = ticketRepository;
}
public ActionResult Index()
{
TravelTicket ticket = new TravelTicket();
ticket.Destination = "USA";
List<Person> travellers = new List<Person>();
travellers.Add(new Person { Name = "Tom" });
travellers.Add(new Person { Name = "Dick" });
travellers.Add(new Person { Name = "Harry" });
ticket.Members = travellers;
ticketRepository.InsertOrUpdate(ticket);
ticketRepository.Save();
Session["Ticket"] = ticket;
return RedirectToAction("Next");
}
public ActionResult Next()
{
TravelTicket ticket = (TravelTicket)Session["Ticket"];
ticket.Members.Add(new Person { Name = "Peter" });
ticket.Members.Add(new Person { Name = "Paul" });
ticketRepository.InsertOrUpdate(ticket);
ticketRepository.Save();
return View();
}
}
The call "ticketRepository.InsertOrUpdate(ticket);" on the "Next" method causes the exception:
An object with the same key already exists in the ObjectStateManager. The ObjectStateManager cannot track multiple objects with the same key.
FURTHER EDIT: If I pull the object back from the database after its been saved instead of pulling the object from the session, adding the 2 new persons works OK:
Works:
TravelTicket ticket = ticketRepository.Find(ticketId);
ticket.Members.Add(new Person { Name = "Peter" });
ticket.Members.Add(new Person { Name = "Paul" });
ticketRepository.InsertOrUpdate(ticket);
ticketRepository.Save();
Doesn't Work:
TravelTicket ticket = (TravelTicket)Session["Ticket"];
ticket.Members.Add(new Person { Name = "Peter" });
ticket.Members.Add(new Person { Name = "Paul" });
ticketRepository.InsertOrUpdate(ticket);
ticketRepository.Save();
I'd need to see the code you are using to add items and then persist them. Until that a few generic advice.
It seems like you're using a long-living context to do your stuff. It's a good practice to use short living context, like this:
Instance context
Do a single operation
Dispose the context
Rinse and repeat for every operation you have to do. While following this good practice, you could be indirectly solving your problem.
Again, for more specific help, please post the code you're using ;)
In your mapping class for person, you may need do something like this
Property(p => p.Id)
.StoreGeneratedPattern = StoreGeneratedPattern.Identity;
List<Student> liStudent = new List<Student>
{
new Student
{
Name="Mohan",ID=1
},
new Student
{
Name="Ravi",ID=2
}
};
public class Student
{
public string Name { get; set; }
public int ID { get; set; }
}
Is there other way to write this? I am a newbie. I want to make instance of student class first and assign properties in list.
List<Student> liStudent = new List<Student>
{
new Student("Mohan",1),
new Student("Ravi",2)
};
public class Student
{
public Student(string name,int id)
{
Name=name;
ID=id;
}
public string Name { get; set; }
public int ID { get; set; }
}
Since Student is a reference type, you can indeed add the instances to the list first, and set their parameters afterwards:
List<Student> lst = new List<Student> { new Student(), new Student() };
lst[0].Name = "Mohan";
lst[0].ID = 1;
lst[1].Name = "Ravi";
lst[1].ID = 2;
It is going to work as you've written in Visual Studio 2008 and 2010. This way you use object initializer, there is no need to invoke a constructor. Read more on How to: Initialize Objects without Calling a Constructor (C# Programming Guide).