Enable C# 8 nullable reference types

Author: RehanSaeed

Benchmarks/Boxed.Mapping.Benchmark/MapArrayBenchmark.cs

@@ -23,7 +23,7 @@ public class MapArrayBenchmark
         private readonly IMapper automapper;
         private readonly IMapper<MapFrom, MapTo> boilerplateMapper;
         private readonly Random random;
-        private MapFrom[] mapFrom;
+        private MapFrom[] mapFrom = default!;
 
         public MapArrayBenchmark()
         {

Benchmarks/Boxed.Mapping.Benchmark/MapListBenchmark.cs

@@ -24,7 +24,7 @@ public class MapListBenchmark
         private readonly IMapper automapper;
         private readonly IMapper<MapFrom, MapTo> boilerplateMapper;
         private readonly Random random;
-        private List<MapFrom> mapFrom;
+        private List<MapFrom> mapFrom = default!;
 
         public MapListBenchmark()
         {

Benchmarks/Boxed.Mapping.Benchmark/MapObjectBenchmark.cs

@@ -23,7 +23,7 @@ public class MapObjectBenchmark
         private readonly IMapper automapper;
         private readonly IMapper<MapFrom, MapTo> boilerplateMapper;
         private readonly Random random;
-        private MapFrom mapFrom;
+        private MapFrom mapFrom = default!;
 
         public MapObjectBenchmark()
         {

Benchmarks/Boxed.Mapping.Benchmark/Models/MapFrom.cs

@@ -12,6 +12,6 @@ public class MapFrom
 
         public long LongFrom { get; set; }
 
-        public string StringFrom { get; set; }
+        public string? StringFrom { get; set; }
     }
 }

Benchmarks/Boxed.Mapping.Benchmark/Models/MapTo.cs

@@ -12,6 +12,6 @@ public class MapTo
 
         public long LongTo { get; set; }
 
-        public string StringTo { get; set; }
+        public string? StringTo { get; set; }
     }
 }

Directory.Build.props

@@ -4,6 +4,7 @@
     <LangVersion>latest</LangVersion>
     <EnforceCodeStyleInBuild>true</EnforceCodeStyleInBuild>
     <AnalysisLevel>latest</AnalysisLevel>
+    <Nullable>enable</Nullable>
     <NeutralLanguage>en-GB</NeutralLanguage>
     <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
   </PropertyGroup>

Source/Boxed.AspNetCore.TagHelpers/HrefSubresourceIntegrityTagHelper.cs

@@ -34,7 +34,7 @@ public HrefSubresourceIntegrityTagHelper(
 
         /// <inheritdoc />
         [HtmlAttributeName(SubresourceIntegrityHrefAttributeName)]
-        public override string Source { get; set; }
+        public override string? Source { get; set; }
 
         /// <inheritdoc />
         protected override string UrlAttributeName => HrefAttributeName;

Source/Boxed.AspNetCore.TagHelpers/HtmlHelperExtensions.cs

@@ -15,7 +15,7 @@ public static class HtmlHelperExtensions
         /// <param name="htmlHelper">The HTML helper.</param>
         /// <param name="referrerMode">The type of referrer allowed to be sent.</param>
         /// <returns>The referrer meta tag.</returns>
-        public static HtmlString ReferrerMeta(this IHtmlHelper htmlHelper, ReferrerMode referrerMode)
+        public static HtmlString? ReferrerMeta(this IHtmlHelper htmlHelper, ReferrerMode referrerMode)
         {
             if (htmlHelper is null)
             {

Source/Boxed.AspNetCore.TagHelpers/OpenGraph/Media/OpenGraphMedia.cs

@@ -12,7 +12,7 @@ public abstract class OpenGraphMedia
         /// Initializes a new instance of the <see cref="OpenGraphMedia"/> class.
         /// </summary>
         /// <param name="mediaUrl">The media URL.</param>
-        /// <exception cref="System.ArgumentNullException">Thrown if <paramref name="mediaUrl"/> is <c>null</c>.</exception>
+        /// <exception cref="ArgumentNullException">Thrown if <paramref name="mediaUrl"/> is <c>null</c>.</exception>
         public OpenGraphMedia(Uri mediaUrl)
         {
             if (mediaUrl is null)
@@ -39,7 +39,7 @@ public OpenGraphMedia(Uri mediaUrl)
         /// Gets or sets the MIME type of the media e.g. media/jpeg. This is optional if your media URL ends with a file extension,
         /// otherwise it is recommended.
         /// </summary>
-        public string Type { get; set; }
+        public string? Type { get; set; }
 
         /// <summary>
         /// Gets the absolute HTTP media URL which should represent your object within the graph.
@@ -49,7 +49,7 @@ public OpenGraphMedia(Uri mediaUrl)
         /// <summary>
         /// Gets the absolute HTTPS media URL which should represent your object within the graph.
         /// </summary>
-        public Uri UrlSecure { get; }
+        public Uri? UrlSecure { get; }
 
         /// <summary>
         /// Appends a HTML-encoded string representing this instance to the <paramref name="stringBuilder"/> containing the Open Graph meta tags.

Source/Boxed.AspNetCore.TagHelpers/OpenGraph/ObjectTypes/Facebook/OpenGraphBooksAuthor.cs

@@ -25,7 +25,7 @@ public class OpenGraphBooksAuthor : OpenGraphMetadata
         /// Gets or sets the URL's to the pages about the books written by the author. This URL must contain books.book meta tags <see cref="OpenGraphBooksBook"/>.
         /// </summary>
         [HtmlAttributeName(BookUrlsAttributeName)]
-        public IEnumerable<string> BookUrls { get; set; }
+        public IEnumerable<string>? BookUrls { get; set; }
 
         /// <summary>
         /// Gets or sets the authors gender.
@@ -37,7 +37,7 @@ public class OpenGraphBooksAuthor : OpenGraphMetadata
         /// Gets or sets the URL's to the pages about the genres of books the author typically writes. This URL must contain books.genre meta tags <see cref="OpenGraphBooksGenre"/>.
         /// </summary>
         [HtmlAttributeName(GenreUrlsAttributeName)]
-        public IEnumerable<string> GenreUrls { get; set; }
+        public IEnumerable<string>? GenreUrls { get; set; }
 
         /// <summary>
         /// Gets the namespace of this open graph type.
@@ -48,7 +48,7 @@ public class OpenGraphBooksAuthor : OpenGraphMetadata
         /// Gets or sets the official site URL of the author.
         /// </summary>
         [HtmlAttributeName(OfficialSiteUrlAttributeName)]
-        public Uri OfficialSiteUrl { get; set; }
+        public Uri? OfficialSiteUrl { get; set; }
 
         /// <summary>
         /// Gets the type of your object. Depending on the type you specify, other properties may also be required.