Add constants for ticker symbols

Closes #28

Bitstamp/BitstampClient.cs

@@ -24,11 +24,21 @@ namespace Bitstamp
     /// <summary>Represents a client for the Bitstamp API.</summary>
     public sealed partial class BitstampClient : IDisposable
     {
+        /// <summary>Gets the BTC/EUR ticker symbol.</summary>
+        public static string BtcEurSymbol => "BTC/EUR";
+
+        /// <summary>Gets the ticker symbol for BTC/EUR.</summary>
+        public static IReadOnlyList<string> TickerSymbols { get; } = new[] { BtcEurSymbol };
+
         /// <summary>Initializes a new instance of the <see cref="BitstampClient"/> class.</summary>
         /// <remarks>An instance initialized with this constructor can be used to access the public API only.</remarks>
         public BitstampClient()
         {
-            this.BtcEur = new BtcEurExchange(this);
+            this.Exchanges =
+                new Dictionary<string, ICurrencyExchange>()
+                {
+                    { BtcEurSymbol, new BtcEurExchange(this) }
+                };
         }
 
         /// <summary>Initializes a new instance of the <see cref="BitstampClient"/> class.</summary>
@@ -57,8 +67,8 @@ public BitstampClient(int customerId, string apiKey, string apiSecret)
             this.sha256 = new HMACSHA256(Encoding.ASCII.GetBytes(apiSecret));
         }
 
-        /// <summary>Gets the exchange for BTCEUR.</summary>
-        public ICurrencyExchange BtcEur { get; }
+        /// <summary>Gets the supported currency exchanges.</summary>
+        public IReadOnlyDictionary<string, ICurrencyExchange> Exchanges { get; }
 
         /// <summary>Releases all resources used by the <see cref="BitstampClient"/>.</summary>
         [SuppressMessage("Microsoft.Design", "CA1031:DoNotCatchGeneralExceptionTypes", Justification = "Dispose must never throw.")]

Bitstamp/BtcEurExchange.cs

@@ -14,7 +14,7 @@ public sealed partial class BitstampClient
         private sealed class BtcEurExchange : CurrencyExchange
         {
             internal BtcEurExchange(BitstampClient client)
-                : base(client, "BTC/EUR")
+                : base(client, BtcEurSymbol)
             {
             }
 

SmartTrade/BtcEurTradeService.cs

@@ -7,12 +7,14 @@
 namespace SmartTrade
 {
     using Android.App;
+    using Bitstamp;
 
     [Service]
     internal sealed class BtcEurTradeService : TradeService
     {
         public BtcEurTradeService()
-            : base(new ExchangeClient(new Settings("BTC/EUR"), c => c.BtcEur))
+            : base(new ExchangeClient(
+                new Settings(BitstampClient.BtcEurSymbol), c => c.Exchanges[BitstampClient.BtcEurSymbol]))
         {
         }
     }

SmartTrade/MainActivity.cs

@@ -6,12 +6,15 @@
 
 namespace SmartTrade
 {
+    using System.Linq;
+
     using Android.App;
     using Android.Content;
     using Android.Content.PM;
     using Android.OS;
     using Android.Views;
     using Android.Widget;
+    using Bitstamp;
 
     [Activity(Label = "@string/AppName", MainLauncher = true, Icon = "@mipmap/icon", ScreenOrientation = ScreenOrientation.Portrait)]
     internal sealed class MainActivity : ActivityBase, AdapterView.IOnItemClickListener
@@ -30,8 +33,8 @@ protected sealed override void OnCreate(Bundle savedInstanceState)
             this.SetContentView(Resource.Layout.Main);
 
             this.tickersListView = this.FindViewById<ListView>(Resource.Id.TickersListView);
-            this.tickersListView.Adapter =
-                new ArrayAdapter<string>(this, Android.Resource.Layout.SimpleListItem1, new[] { "BTC/EUR" });
+            this.tickersListView.Adapter = new ArrayAdapter<string>(
+                this, Android.Resource.Layout.SimpleListItem1, BitstampClient.TickerSymbols.ToArray());
             this.tickersListView.OnItemClickListener = this;
         }