Question

I am wanting to find out if there is a way to initialize a List<T> where T is an object much like a simple collection gets initialized?

Simple Collection Initializer:

List<int> digits = new List<int> { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };

Object Collection Initilizer:

 List<ChildObject> childObjects = new List<ChildObject>
 {       
        new ChildObject(){ Name = "Sylvester", Age=8 },
        new ChildObject(){ Name = "Whiskers", Age=2 },
        new ChildObject(){ Name = "Sasha", Age=14 }
 };

The question is, how and if you can do something like this?

 List<ChildObject> childObjects = new List<ChildObject>
 {       
       { "Sylvester", 8} , {"Whiskers", 2}, {"Sasha", 14}
 };

Answer 1

You can’t do this without creating your own class derived from List<ChildObject> as per Lee’s answer. It’s unfortunate that extension methods aren’t considered for collection initalizers, otherwise this would work:

// This doesn't work, but it would if collection initializers checked
// extension methods.
using System;
using System.Collections.Generic;

public class ChildObject
{
    public string Name { get; set; }
    public int Age { get; set; }
}

public static class Extensions
{
    public static void Add(this List<ChildObject> children, 
                           string name, int age)
    {
        children.Add(new ChildObject { Name = name, Age = age });
    }
}

class Test
{
    static void Main(string[] args)
    {
        List<ChildObject> children = new List<ChildObject>
        {
            { "Sylvester", 8 },
            { "Whiskers", 2 },
            { "Sasha", 14 }
        };
    }
}