Generic List

Question

Hi friends. I am trying to debug this code so that I can see the value that I added to the variable list1, but when I hover over the variable after adding 1 to the list it doesnt show me anything. Am I debugging this Generic wrong?

 public class GenericList<T>  
        {  
            public void Add(T input) { }  
        }  
        
    class TestGenericList  
    {  
         static void Main()  
        {  
            // Declare a list of type int.  
            GenericList<int> list1 = new GenericList<int>();  
            list1.Add(1);  
        }  
    }  
  
  
  
  

Answer 1

This will work, no need to create an Add method and if so you are hiding the base Add method.

using System;  
using System.Collections.Generic;  
  
namespace ForumQuestion  
{  
    partial class Program  
    {  
        private static readonly GenericList<int> _list = new();  
        static void Main(string[] args)  
        {  
  
            for (int index = 0; index < 5; index++)  
            {  
                _list.Add(index);  
            }  
  
            Console.WriteLine(string.Join(",", _list));  
            Console.ReadLine();  
        }  
    }  
  
    public class GenericList<T> : List<T> { }  
}  
  

Answer 2

There is a generic list implemented in .NET, List<T>, you even do not need to derive from it. Just use it like this:

var list = new List<int>();  
list.Add(1);  

Then the list will contain an item.

If this is an assignment or for learning purpose you want to implement a generic list class from scratch then you can take a look at source code of List<T> or you can extend the following code:

using System;  
public class MyList<T>  
{  
    private T[] items = new T[] { };  
    public void Add(T item)  
    {  
        T[] newItems = new T[items.Length + 1];  
        if (items.Length > 0)  
            Array.Copy(items, 0, newItems, 0, items.Length);  
        items = newItems;  
        items[items.Length - 1] = item;  
    }  
    public void RemoveAt(int index)  
    {  
        if (index > items.Length - 1)  
            throw new IndexOutOfRangeException();  
        if (index < items.Length - 1)  
        {  
            Array.Copy(items, index + 1, items, index, items.Length - index - 1);  

        }  
        T[] newItems = new T[items.Length - 1];  
        if (items.Length - 1 > 0)  
            Array.Copy(items, 0, newItems, 0, items.Length - 1);  
        items = newItems;  
    }  
    public T this[int index]  
    {  
        get  
        {  
            return items[index];  
        }  
        set  
        {  
            items[index] = value;  
        }  
    }  
}   

Answer 3

your code:

         public class GenericList<T>  
         {  
             public void Add(T input) { }  
         }  

the Add method doesn't do anything passed input. as the class has no public properties, there is nothing for the debugger to display; typically a list class would implement IEnumerable<T> interface.

    public class GenericList<T> : IEnumerable<T>  
    {  
        private T[] items = new T[] { };  
  
        public GenericList() { }  
  
        public void Add(T input)  
        {  
            items = items.Append(input).ToArray();  
        }  
  
        public T Get(int i) => items[i];  
  
        public int Count => items.Length;  
  
        public IEnumerator<T> GetEnumerator() => new Enumerator(this);  
          
        IEnumerator IEnumerable.GetEnumerator() => new Enumerator(this);  
  
        public class Enumerator : IEnumerator<T>  
        {  
            private GenericList<T> list;  
            private int index = -1;  
  
            internal Enumerator(GenericList<T> items)  
            {  
                list = items;  
            }  
  
            public T Current => list.Get(index);  
  
            object? IEnumerator.Current => Current;  
  
            public void Dispose() { }  
  
            public bool MoveNext() => ++index < list.Count;  
  
            public void Reset()  
            {  
                index = -1;  
            }  
        }  
    }  

Answer 4

For example, try this:

public class GenericList<T> : List<T>  
{  
}