C# – syntactic sugar C# property syntax to instantiate generic collections

cpropertiessyntax

The following program will fail because Contracts is not instantiated.

Of course I can instantiate it in my constructor but if I have dozens of properties and/or multiple constructors I have to keep track of which are instantiated, etc.

And of course I could create large blocks for these properties with full gets and sets and private field variables, etc. But this gets messy as well.

Isn't there a way to automatically instantiate these collections with the nice C# property syntax?

using System;
using System.Collections.Generic;

namespace TestProperty232
{
    class Program
    {
        static void Main(string[] args)
        {
            Customer customer = new Customer();
            customer.FirstName = "Jim";
            customer.LastName = "Smith";

            Contract contract = new Contract();
            contract.Title = "First Contract";

            customer.Contracts.Add(contract);

            Console.ReadLine();
        }
    }

    public class Customer
    {
        public string FirstName { get; set; }
        public string LastName { get; set; }
        public List<Contract> Contracts { get; set; }

        public Customer()
        {
            //Contracts = new List<Contract>();
        }
    }

    public class Contract
    {
        public string Title { get; set; }
    }
}

Best Answer

There is no such syntactic sugar, but I'd like to point out a few things:

Collection properties should be read-only in any case.
If you have a lot of such properties in a single type, it's a strong symptom that you are violating the Single Responsibility Principle
If you have multiple constructors, you should always take great care that there's only one constructor that does the real work, and all other constructors delegate to that constructor. Alternatively you can delegate all constructor work to a private Initialize method.

Related Solutions

C# – Can use interfaces in creating the models in Entity Framework Codefirst

First of all, it sounds like you are confusing inheritance and composition. An example of inheritance would be having a common Person base class from which you could inherit an Employee or a Student. An example of composition would be an Employee and a Supplier each composed with a common ContactInfo object, but having no common base class.

When you design your entities, you are really designing the table structure of the underlying relational database. You can model inheritance: a common base class can be represented by its own table and any common fields, and any specialized classes could be in their own table with a foreign key linking to the common table. It may or may not make sense to do this - by breaking things up into separate tables, you're adding another join to your queries. This will slow down performance.

Composition can also be represented in a relational database, but it only really makes sense if it is a common component shared amongst many other data entities. ContactInfo is almost always going to be unique for a given person/supplier, so it really doesn't make sense to break it out into a separate table - you're just adding an extra table join which, again, will slow down performance on your queries.

You should think about moving inheritance/composition up a layer in your design. The entities (data access layer) should match the relational database, but the domain model (i.e. business objects layer) should adhere to object-oriented principles.

C# – How to change the table names when using ASP.NET Identity

You can do this easily by modifying the IdentityModel.cs as per the below:

Override OnModelCreating in your DbContext then add the following, this will change AspNetUser table to "Users" you can also change the field names the default Id column will become User_Id.

modelBuilder.Entity<IdentityUser>()
                    .ToTable("Users", "dbo").Property(p => p.Id).HasColumnName("User_Id");

or simply the below if you want to keep all the standard column names:

modelBuilder.Entity<IdentityUser>()
                        .ToTable("Users", "dbo")

Full example below (this should be in your IdentityModel.cs file) i changed my ApplicationUser class to be called User.

public class User : IdentityUser
    {
        public string PasswordOld { get; set; }
        public DateTime DateCreated { get; set; }

        public bool Activated { get; set; }

        public bool UserRole { get; set; }

    }

public class ApplicationDbContext : IdentityDbContext<User>
    {
        public ApplicationDbContext()
            : base("DefaultConnection")
        {
        }

        protected override void OnModelCreating(System.Data.Entity.DbModelBuilder modelBuilder)
        {
            base.OnModelCreating(modelBuilder);
            modelBuilder.Entity<IdentityUser>()
                .ToTable("Users", "dbo").Property(p => p.Id).HasColumnName("User_Id");
            modelBuilder.Entity<User>()
                .ToTable("Users", "dbo").Property(p => p.Id).HasColumnName("User_Id");
        }
    }

Please note i have not managed to get this working if the current table exists. Also note whatever columns you do not map the default ones will be created.

Hope that helps.

Best Answer

Related Solutions

C# – Can use interfaces in creating the models in Entity Framework Codefirst

C# – How to change the table names when using ASP.NET Identity

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