Generic Collections

Author: Luay Younus Version: 1.0

Overview

An Ecommerce store that demonstrates creating Array Add/Remove/AtIndex methods through Collection initializers. Xunit tests are written to prove the List resizing mechanism.

Requirements to run the Application

• Visual Studio 2017 Community with .NET Core 2.0 SDK
• GitBash / Terminal or GitHub Extension for Visual Studio

Getting Started

1. Clone the repository to your local machine.
2. Cd into the application directory where the AppName.sln exist.
3. Open the application using Open/Start AppName.sln.
4. Once Visual Studio is opened, you can Run the application by clicking on the Play button .
5. A demo will be presented showing both C# built in Arrays Vs. custom array through Collection Initializers in Console statements.

Inventory Explanation

Inventory class is implementing the custom Array method by first implementing IEnumerable

public class Inventory<T> : IEnumerable<T>

The class consists of the following main properties giving the Array a size of 2 for a start

public T[] Items = new T[2];
public int Count = 0;

The two required IEnumerable methods are implemented as the following

public IEnumerator<T> GetEnumerator()
{
    for (int i = 0; i < Count; i++)
    {
        yield return Items[i];
    }
}

IEnumerator IEnumerable.GetEnumerator()
{
    return GetEnumerator();
}

Add method implementation, increasing the Array size when more Items are added

public void Add(T item)
{
    if (Count == (Items.Length / 2))
    {
        T[] newArray = new T[Items.Length * 2];

        for (int i = 0; i < Items.Length; i++)
        {
            newArray[i] = Items[i];
        }

        Items = newArray;
    }
    Items[Count] = item;
    Count++;
}

Remove method implementation, decreasing the Array size when Items are removed

public void Remove(T item)
{
    T[] newArray = new T[Items.Length];
    if (Count - 1 <= Items.Length / 2)
    {
        newArray = new T[Items.Length / 2];
    }

    int j = 0;
    int tempCount = Count;
    for (int i = 0; i < tempCount; i++)
    {
        if (j >= tempCount) break;
        if (!item.Equals(Items[j]))
        {
            newArray[i] = Items[j];
            j++;
        }
        else
        {
            Count--;
            i--;
            j++;
        }
    }
    Items = newArray;
}

Getting Index for an Item

public int AtIndexOf(T item)
{
    for (int i = 0; i < Count; i++)
    {
        if (Items[i].Equals(item))
        {
            return i;
        }
    }
    throw new InvalidOperationException();
}

The Inventory app consists of a product class that uses a product Enum

Product

public class Product
{
    public string Name { get; set; }
    public ProductType Type { get; set; }

    public Product(string name, ProductType type)
    {
        Name = name;
        Type = type;
    }
}

Product Enum

public enum ProductType
{
    Movies,
    Home,
    Health,
    Grocery
}

The following are the Test Cases implemented to check different Scenarios

[Fact]
public void Return_Equal_Inventory_Count_When_Adding()
{
    // Arrange
    Product product = new Product("Computer", ProductType.Home);
    Inventory<Product> inventory = new Inventory<Product>();

    // Act
    inventory.Add(product);

    // Assert
    Assert.Equal(1, inventory.Count);
}

[Fact]
public void Return_Inventory_Half_Size_When_Removing()
{
    // Arrange
    Product product = new Product("Chair", ProductType.Home);
    Inventory<Product> inventory = new Inventory<Product>();

    // Act
    inventory.Add(product);
    inventory.Remove(product); // Resizing array to half after removing

    // Assert
    Assert.Equal(1, inventory.Items.Length);
}

[Fact]
public void Throw_Exception_When_Product_Not_Found()
{
    // Arrange
    Product product = new Product("Table", ProductType.Home);
    Inventory<Product> inventory = new Inventory<Product>();

    // Act & Assert
    Assert.Throws<InvalidOperationException>(() => inventory.AtIndexOf(product));
}

Architecture

• C# Console Core application.
• Inventory Class that implements Add/Remove/AtIndex methods.
• Product Class.
• Enum for Product Types.