added redis integration and command line arguments handling to cart service. Didn't test in the cloud yet

.gitignore

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+src/cartservice/bin/*
+src/cartservice/obj/*
+.vs/*.*

.vscode/launch.json

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+{
+   // Use IntelliSense to find out which attributes exist for C# debugging
+   // Use hover for the description of the existing attributes
+   // For further information visit https://github.com/OmniSharp/omnisharp-vscode/blob/master/debugger-launchjson.md
+   "version": "0.2.0",
+   "configurations": [
+        {
+            "name": ".NET Core Launch (console)",
+            "type": "coreclr",
+            "request": "launch",
+            "preLaunchTask": "build",
+            // If you have changed target frameworks, make sure to update the program path.
+            "program": "${workspaceFolder}/src/cartservice/bin/Debug/netcoreapp2.0/cartservice.dll",
+            "args": [],
+            "cwd": "${workspaceFolder}/src/cartservice",
+            // For more information about the 'console' field, see https://github.com/OmniSharp/omnisharp-vscode/blob/master/debugger-launchjson.md#console-terminal-window
+            "console": "internalConsole",
+            "stopAtEntry": false,
+            "internalConsoleOptions": "openOnSessionStart"
+        },
+        {
+            "name": ".NET Core Attach",
+            "type": "coreclr",
+            "request": "attach",
+            "processId": "${command:pickProcess}"
+        }
+    ,]
+}

.vscode/tasks.json

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+{
+    "version": "2.0.0",
+    "tasks": [
+        {
+            "label": "build",
+            "command": "dotnet",
+            "type": "process",
+            "args": [
+                "build",
+                "${workspaceFolder}/src/cartservice/cartservice.csproj"
+            ],
+            "problemMatcher": "$msCompile"
+        }
+    ]
+}

src/cartservice/cartstore/LocalCartStore.cs

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+using System.Collections.Concurrent;
+using cartservice.interfaces;
+
+namespace cartservice.cartstore
+{
+    internal class LocalCartStore 
+    {
+        // Maps between user and their cart
+        private ConcurrentDictionary<string, Cart> userCartItems = new ConcurrentDictionary<string, Cart>();
+
+        public void AddItem(string userId, string productId, int quantity)
+        {
+            Cart cart;
+            if (!userCartItems.TryGetValue(userId, out cart))
+            {
+                cart = new Cart(userId);
+            }
+            else
+            {
+                cart = userCartItems[userId];
+            }
+            cart.AddItem(productId, quantity);
+        }
+
+        public void EmptyCart(string userId)
+        {
+            Cart cart;
+            if (userCartItems.TryGetValue(userId, out cart))
+            {
+                cart.EmptyCart();
+            }
+        }
+
+        public Cart GetCart(string userId)
+        {
+            Cart cart = null;
+            userCartItems.TryGetValue(userId, out cart);
+            return cart;
+        }
+    }
+}

src/cartservice/cartstore/RedisCartStore.cs

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+using System;
+using System.IO;
+using System.Threading.Tasks;
+using cartservice.interfaces;
+using Google.Protobuf;
+using Hipstershop;
+using StackExchange.Redis;
+
+namespace cartservice.cartstore
+{
+    public class RedisCartStore : ICartStore
+    {
+        private const string CART_FIELD_NAME = "cart";
+
+        private readonly ConnectionMultiplexer redis;
+
+        private readonly byte[] emptyCartBytes;
+
+        public RedisCartStore(string redisAddress)
+        {
+            // Serialize empty cart into byte array.
+            var cart = new Hipstershop.Cart();
+            emptyCartBytes = cart.ToByteArray();
+
+            string connectionString = $"{redisAddress},ssl=false,allowAdmin=true";
+            Console.WriteLine("Connecting to Redis: " + connectionString);
+            redis = ConnectionMultiplexer.Connect(connectionString);
+        }
+
+        public async Task AddItemAsync(string userId, string productId, int quantity)
+        {
+            var db = redis.GetDatabase();
+            
+            // Access the cart from the cache
+            var value = await db.HashGetAsync(userId, CART_FIELD_NAME);
+
+            Hipstershop.Cart cart;
+            if (value.IsNull)
+            {
+                cart = new Hipstershop.Cart();
+            }
+            else
+            {
+                cart = Hipstershop.Cart.Parser.ParseFrom(value);
+            }
+
+            cart.Items.Add(new Hipstershop.CartItem { ProductId = productId, Quantity = quantity });
+        }
+
+        public async Task EmptyCartAsync(string userId)
+        {
+            var db = redis.GetDatabase();
+
+            // Update the cache with empty cart for given user
+            await db.HashSetAsync(userId, new[] { new HashEntry(CART_FIELD_NAME, emptyCartBytes) });
+        }
+
+        public async Task<Hipstershop.Cart> GetCartAsync(string userId)
+        {
+            var db = redis.GetDatabase();
+
+            // Access the cart from the cache
+            var value = await db.HashGetAsync(userId, CART_FIELD_NAME);
+
+            Hipstershop.Cart cart = null;
+            if (!value.IsNull)
+            {
+                cart = Hipstershop.Cart.Parser.ParseFrom(value);
+            }
+
+            return cart;
+        }
+    }
+}

src/cartservice/interfaces/ICartStore.cs

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+using System.Threading.Tasks;
+
+namespace cartservice.interfaces
+{
+    internal interface ICartStore
+    {
+        Task AddItemAsync(string userId, string productId, int quantity);
+        Task EmptyCartAsync(string userId);
+
+        Task<Hipstershop.Cart> GetCartAsync(string userId);
+    }
+}

src/cartservice/run_redis_emulator_windows.bat

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+@echo off
+rem install redis on windows using choco
+rem choco install redis-64
+
+rem run redis
+redis-server --daemonize yes
+
+rem testing locally
+rem redis-cli
+rem SET foo bar
+rem GET foo