Use nullability tags

src/NmeaParser.sln

@@ -1,7 +1,7 @@
 
 Microsoft Visual Studio Solution File, Format Version 12.00
-# Visual Studio 15
+# Visual Studio 16
-VisualStudioVersion = 15.0.27130.2003
+VisualStudioVersion = 16.0.0.0
 MinimumVisualStudioVersion = 10.0.40219.1
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "NmeaParser", "NmeaParser", "{1701F3BA-A09C-4706-A612-24FD9340FC18}"
 EndProject

src/NmeaParser/BluetoothDevice.Android.cs

@@ -29,7 +29,7 @@ namespace NmeaParser
 	{
         private static Java.Util.UUID SERIAL_UUID = Java.Util.UUID.FromString("00001101-0000-1000-8000-00805F9B34FB");
         private Android.Bluetooth.BluetoothDevice m_device;
-        private BluetoothSocket m_socket;
+        private BluetoothSocket? m_socket;
 
         /// <summary>
         /// Gets a list of bluetooth devices that supports serial communication
@@ -51,7 +51,7 @@ namespace NmeaParser
 		/// <param name="device">The Android Bluetooth Device.</param>
 		public BluetoothDevice(Android.Bluetooth.BluetoothDevice device)
 		{
-            m_device = device;
+            m_device = device ?? throw new ArgumentNullException(nameof(device));
 		}
         
         /// <summary>
@@ -80,7 +80,7 @@ namespace NmeaParser
 			if (stream == null)
 				throw new ArgumentNullException("stream");
 			stream.Dispose();
-			m_socket.Dispose();
+			m_socket?.Dispose();
 			m_socket = null;
 			return Task.FromResult(true);
 		}

src/NmeaParser/BluetoothDevice.UWP.cs

@@ -33,9 +33,9 @@ namespace NmeaParser
 	/// </summary>
 	public class BluetoothDevice : NmeaDevice
 	{
-		private Windows.Devices.Bluetooth.Rfcomm.RfcommDeviceService m_deviceService;
+		private Windows.Devices.Bluetooth.Rfcomm.RfcommDeviceService? m_deviceService;
-        private Windows.Networking.Proximity.PeerInformation m_devicePeer;
+        private Windows.Networking.Proximity.PeerInformation? m_devicePeer;
-        private StreamSocket m_socket;
+        private StreamSocket? m_socket;
         private bool m_disposeService;
         private SemaphoreSlim m_semaphoreSlim = new SemaphoreSlim(1, 1);
 
@@ -60,7 +60,7 @@ namespace NmeaParser
         /// <param name="disposeService">Whether this devicee should also dispose the RfcommDeviceService provided when this device disposes.</param>
         public BluetoothDevice(RfcommDeviceService service, bool disposeService = false)
 		{
-			m_deviceService = service;
+			m_deviceService = service ?? throw new ArgumentNullException(nameof(service));
             m_disposeService = disposeService;
         }
 
@@ -70,7 +70,7 @@ namespace NmeaParser
         /// <param name="peer">The peer information device.</param>
         public BluetoothDevice(Windows.Networking.Proximity.PeerInformation peer)
         {
-            m_devicePeer = peer;
+            m_devicePeer = peer ?? throw new ArgumentNullException(nameof(peer));
         }
 
         /// <inheritdoc />
@@ -95,20 +95,37 @@ namespace NmeaParser
             {
                 await socket.ConnectAsync(m_devicePeer.HostName, "1");
             }
-            else
+            else if (m_deviceService != null)
             {
                 await socket.ConnectAsync(m_deviceService.ConnectionHostName, m_deviceService.ConnectionServiceName);
             }
+            else
+                throw new InvalidOperationException();
 			m_socket = socket;
-            return null; //We're going to use WinRT buffers instead and will handle read/write, so no reason to return a stream. This is mainly done to avoid locking issues reading and writing at the same time
+            
+            return new DummyStream(); //We're going to use WinRT buffers instead and will handle read/write, so no reason to return a real stream. This is mainly done to avoid locking issues reading and writing at the same time
 		}
 
-		/// <summary>
+        private class DummyStream : Stream
-		/// Closes the stream the NmeaDevice is working on top off.
+        {
-		/// </summary>
+            public override bool CanRead => false;
-		/// <param name="stream">The stream.</param>
+            public override bool CanSeek => false;
-		/// <returns></returns>
+            public override bool CanWrite => false;
-		protected override Task CloseStreamAsync(System.IO.Stream stream)
+            public override long Length => throw new NotSupportedException();
+            public override long Position { get => throw new NotSupportedException(); set => throw new NotSupportedException(); }
+            public override void Flush() => throw new NotSupportedException();
+            public override int Read(byte[] buffer, int offset, int count) => throw new NotSupportedException();
+            public override long Seek(long offset, SeekOrigin origin) => throw new NotSupportedException();
+            public override void SetLength(long value) => throw new NotSupportedException();
+            public override void Write(byte[] buffer, int offset, int count) => throw new NotSupportedException();
+        }
+
+        /// <summary>
+        /// Closes the stream the NmeaDevice is working on top off.
+        /// </summary>
+        /// <param name="stream">The stream.</param>
+        /// <returns></returns>
+        protected override Task CloseStreamAsync(System.IO.Stream stream)
 		{
             if(m_socket == null)
                 throw new InvalidOperationException("No connection to close");
@@ -124,6 +141,8 @@ namespace NmeaParser
             // Reading and writing to the Bluetooth serial connection at the same time seems very unstable in UWP,
             // so we use a semaphore to ensure we don't read and write at the same time
             await m_semaphoreSlim.WaitAsync().ConfigureAwait(false);
+            if (m_socket == null)
+                throw new InvalidOperationException("Socket not initialized");
             try
             {
                 var r = await m_socket.InputStream.ReadAsync(buffer.AsBuffer(), (uint)count, Windows.Storage.Streams.InputStreamOptions.None);

src/NmeaParser/BufferedStreamDevice.cs

@@ -27,7 +27,7 @@ namespace NmeaParser
 	/// </summary>
 	public abstract class BufferedStreamDevice : NmeaDevice
 	{
-		private BufferedStream m_stream;
+		private BufferedStream? m_stream;
 		private readonly int m_readSpeed;
 
 		/// <summary>
@@ -71,7 +71,7 @@ namespace NmeaParser
 		/// <returns></returns>
 		protected override Task CloseStreamAsync(System.IO.Stream stream)
 		{
-			m_stream.Dispose();
+			m_stream?.Dispose();
 			return Task.FromResult(true);
 		}
 
@@ -83,8 +83,8 @@ namespace NmeaParser
 			private byte[] m_buffer = new byte[0];
 			private readonly System.Threading.Timer m_timer;
 			private readonly object lockObj = new object();
-			private string groupToken = null;
+			private string? groupToken = null;
-			private string lastLineRead = null;
+			private string? lastLineRead = null;
 			/// <summary>
 			/// Initializes a new instance of the <see cref="BufferedStream"/> class.
 			/// </summary>

src/NmeaParser/Nmea/Bod.cs

@@ -63,11 +63,11 @@ namespace NmeaParser.Nmea
         /// <summary>
         /// Name of origin
         /// </summary>
-        public string OriginId { get; }
+        public string? OriginId { get; }
 
         /// <summary>
         /// Name of destination
         /// </summary>
-        public string DestinationId { get; }
+        public string? DestinationId { get; }
     }
 }

src/NmeaParser/Nmea/Gns.cs

@@ -228,7 +228,7 @@ namespace NmeaParser.Nmea
 		/// <summary>
 		/// eference station ID1, range 0000-4095 - Null if talker ID is GN, additional GNS messages follow with GP and/or GL Reference station ID
         /// </summary>
-        public string DgpsStationId { get; }
+        public string? DgpsStationId { get; }
 
         /// <summary>
         /// Navigational status

src/NmeaParser/NmeaDevice.cs

@@ -29,10 +29,10 @@ namespace NmeaParser
 	{
 		private readonly object m_lockObject = new object();
 		private string m_message = "";
-		private Stream m_stream;
+		private Stream? m_stream;
-		private CancellationTokenSource m_cts;
+		private CancellationTokenSource? m_cts;
 		private bool m_isOpening;
-        private Task m_ParserTask;
+        private Task? m_ParserTask;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="NmeaDevice"/> class.
@@ -183,7 +183,9 @@ namespace NmeaParser
 
         private void OnMessageReceived(Nmea.NmeaMessage msg)
         {
-            Nmea.NmeaMessage[] messageParts = null;
+            if (msg == null)
+                return;
+            Nmea.NmeaMessage[]? messageParts = null;
             if (msg is IMultiPartMessage multi)
             {
                 string messageType = msg.MessageType.Substring(2); //We don't care about the two first characters. Ie GPGSV, GLGSV, GAGSV etc are all part of the same multi-part message
@@ -212,8 +214,8 @@ namespace NmeaParser
                     }
                 }
             }
-
+            if (messageParts != null)
-            MessageReceived?.Invoke(this, new NmeaMessageReceivedEventArgs(msg, messageParts));
+                MessageReceived?.Invoke(this, new NmeaMessageReceivedEventArgs(msg, messageParts));
         }
 
 		private readonly Dictionary<string, Dictionary<int, Nmea.NmeaMessage>> MultiPartMessageCache = new Dictionary<string,Dictionary<int,Nmea.NmeaMessage>>();

src/NmeaParser/NmeaFileDevice.cs

@@ -27,7 +27,7 @@ namespace NmeaParser
 	public class NmeaFileDevice : BufferedStreamDevice
 	{
 #if NETFX_CORE
-		private Windows.Storage.IStorageFile m_storageFile;
+		private Windows.Storage.IStorageFile? m_storageFile;
 #endif
         private string m_filename;
 
@@ -44,8 +44,8 @@ namespace NmeaParser
         /// <summary>
         /// Initializes a new instance of the <see cref="NmeaFileDevice"/> class.
         /// </summary>
-        /// <param name="fileName"></param>
+        /// <param name="storageFile"></param>
-        public NmeaFileDevice(Windows.Storage.IStorageFile fileName) : this(fileName, 1000)
+        public NmeaFileDevice(Windows.Storage.IStorageFile storageFile) : this(storageFile, 1000)
 		{
 		}
 #endif
@@ -63,12 +63,13 @@ namespace NmeaParser
         /// <summary>
         /// Initializes a new instance of the <see cref="NmeaFileDevice"/> class.
         /// </summary>
-        /// <param name="fileName"></param>
+        /// <param name="storageFile"></param>
         /// <param name="readSpeed">The time to wait between each group of lines being read in milliseconds</param>
-        public NmeaFileDevice(Windows.Storage.IStorageFile fileName, int readSpeed)
+        public NmeaFileDevice(Windows.Storage.IStorageFile storageFile, int readSpeed)
             : base(readSpeed)
         {
-            m_storageFile = fileName;
+            m_storageFile = storageFile ?? throw new ArgumentNullException(nameof(storageFile));
+            m_filename = storageFile.Path;
         }
 #endif
 
@@ -79,10 +80,6 @@ namespace NmeaParser
 		{
 			get
             {
-#if NETFX_CORE
-                if (m_storageFile != null)
-                    return m_storageFile.Path;
-#endif
                 return m_filename;
             }
 		}

src/NmeaParser/NmeaParser.csproj

@@ -27,9 +27,10 @@ Updated license to Apache 2.0</PackageReleaseNotes>
     <PublishRepositoryUrl>true</PublishRepositoryUrl>
     <EmbedUntrackedSources>true</EmbedUntrackedSources>
     <AllowedOutputExtensionsInPackageBuildOutputFolder>$(AllowedOutputExtensionsInPackageBuildOutputFolder);.pdb</AllowedOutputExtensionsInPackageBuildOutputFolder>
-    <LangVersion>7.3</LangVersion>
+    <LangVersion>8.0</LangVersion>
     <TreatWarningsAsErrors Condition="'$(Configuration)'=='Release'">true</TreatWarningsAsErrors>
     <CodeAnalysisTreatWarningsAsErrors Condition="'$(Configuration)'=='Release'">true</CodeAnalysisTreatWarningsAsErrors>
+    <Nullable>enable</Nullable>
   </PropertyGroup>
   
   <PropertyGroup Condition="'$(TargetFramework)' == 'netstandard1.4'">
@@ -41,11 +42,13 @@ Updated license to Apache 2.0</PackageReleaseNotes>
   </PropertyGroup>
 
   <PropertyGroup Condition="'$(TargetFramework)' == 'monoandroid50'">
+    <DesignTimeBuild>false</DesignTimeBuild> <!-- workaround for MSBuildSdkExtras issue in VS16.2 -->
     <DefineConstants>$(DefineConstants);XAMARIN;API_LEVEL_21</DefineConstants>
     <NoWarn>$(NoWarn);XA0113;XA0114</NoWarn>
     <AndroidEnableGooglePlayStoreChecks>false</AndroidEnableGooglePlayStoreChecks>
   </PropertyGroup>
   <PropertyGroup Condition="'$(TargetFramework)' == 'monoandroid70'">
+    <DesignTimeBuild>false</DesignTimeBuild> <!-- workaround for MSBuildSdkExtras issue in VS16.2 -->
     <DefineConstants>$(DefineConstants);XAMARIN;API_LEVEL_24</DefineConstants>
     <NoWarn>$(NoWarn);XA0113;XA0114</NoWarn>
     <AndroidEnableGooglePlayStoreChecks>false</AndroidEnableGooglePlayStoreChecks>

src/NmeaParser/SerialPortDevice.Desktop.cs

@@ -64,7 +64,7 @@ namespace NmeaParser
 		{
             if (Port.IsOpen)
                 Port.Close();
-			return Task.FromResult<object>(null);
+			return Task.FromResult<object?>(null);
 		}
 
 		/// <summary>
@@ -90,7 +90,7 @@ namespace NmeaParser
                 throw new InvalidOperationException("Device not open");
 
             Port.Write(buffer, offset, length);
-            return Task.FromResult<object>(null);
+            return Task.FromResult<object?>(null);
         }
     }
 }

src/NmeaParser/StreamDevice.cs

@@ -33,7 +33,7 @@ namespace NmeaParser
 		/// <param name="stream">The stream.</param>
 		public StreamDevice(Stream stream) : base()
 		{
-			m_stream = stream;
+			m_stream = stream ?? throw new ArgumentNullException(nameof(stream));
 		}
 
 		/// <summary>
@@ -64,7 +64,6 @@ namespace NmeaParser
 			base.Dispose(disposing);
 			if (m_stream != null)
 				m_stream.Dispose();
-			m_stream = null;
 		}
 
         /// <inheritdoc />

src/NmeaParser/SystemNmeaDevice.Android.cs

@@ -32,16 +32,18 @@ namespace NmeaParser
     /// </summary>
     public class SystemNmeaDevice : NmeaDevice
     {
-        private StringStream stream;
+        private StringStream? stream;
-        private Listener listener;
+        private Listener? listener;
         private LocationManager manager;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="SystemNmeaDevice"/> class.
         /// </summary>
-        public SystemNmeaDevice()
+        public SystemNmeaDevice(Context context)
         {
-            manager = Application.Context.GetSystemService(Context.LocationService) as LocationManager;
+            if (context == null)
+                throw new ArgumentNullException(nameof(context));
+            manager = context.GetSystemService(Context.LocationService) as LocationManager ?? throw new InvalidOperationException("Cannot acces the Location Service");
         }
 
         /// <summary>
@@ -76,10 +78,10 @@ namespace NmeaParser
         {
             manager.RemoveUpdates(listener);
             manager.RemoveNmeaListener(listener);
-            listener.Dispose();
+            listener?.Dispose();
             listener = null;
             stream.Dispose();
-            return Task.FromResult<object>(null);
+            return Task.CompletedTask;
         }
 
         private class Listener : Java.Lang.Object,

src/SampleApp.Droid/MainActivity.cs

@@ -96,7 +96,7 @@ namespace SampleApp.Droid
                     return;
 
                 launched = true;
-                listener = new NmeaParser.SystemNmeaDevice();
+                listener = new NmeaParser.SystemNmeaDevice(ApplicationContext);
             }
             else //Bluetooth
             {