Enable C# 8 nullable reference types

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.

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

@@ -32,13 +32,13 @@ public class OpenGraphBooksBook : OpenGraphMetadata
         /// Gets or sets the URL's to the pages about the authors of the book. This URL must contain books.author meta tags <see cref="OpenGraphBooksAuthor"/>.
         /// </summary>
         [HtmlAttributeName(AuthorUrlsAttributeName)]
-        public IEnumerable<string> AuthorUrls { get; set; }
+        public IEnumerable<string>? AuthorUrls { get; set; }
 
         /// <summary>
         /// Gets or sets the URL's to the pages about the genres of the book. 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 or sets the initial release date of the book.
@@ -50,13 +50,13 @@ public class OpenGraphBooksBook : OpenGraphMetadata
         /// Gets or sets the books unique ISBN number.
         /// </summary>
         [HtmlAttributeName(ISBNAttributeName)]
-        public string ISBN { get; set; }
+        public string? ISBN { get; set; }
 
         /// <summary>
         /// Gets or sets the language of the book in the format language_TERRITORY.
         /// </summary>
         [HtmlAttributeName(LanguageAttributeName)]
-        public string Language { get; set; }
+        public string? Language { get; set; }
 
         /// <summary>
         /// Gets the namespace of this open graph type.
@@ -73,7 +73,7 @@ public class OpenGraphBooksBook : OpenGraphMetadata
         /// Gets or sets the rating of the book.
         /// </summary>
         [HtmlAttributeName(RatingAttributeName)]
-        public OpenGraphRating Rating { get; set; }
+        public OpenGraphRating? Rating { get; set; }
 
         /// <summary>
         /// Gets or sets the release date of the book.
@@ -85,7 +85,7 @@ public class OpenGraphBooksBook : OpenGraphMetadata
         /// Gets or sets the URL to a sample of the book.
         /// </summary>
         [HtmlAttributeName(SampleUrlAttributeName)]
-        public Uri SampleUrl { get; set; }
+        public Uri? SampleUrl { get; set; }
 
         /// <summary>
         /// Gets the type of your object. Depending on the type you specify, other properties may also be required.

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

@@ -25,19 +25,19 @@ public class OpenGraphBooksGenre : OpenGraphMetadata
         /// Gets or sets the URL's to the pages about the authors who wrote the books. This URL must contain books.book meta tags <see cref="OpenGraphBooksAuthor"/>.
         /// </summary>
         [HtmlAttributeName(AuthorUrlsAttributeName)]
-        public IEnumerable<string> AuthorUrls { get; set; }
+        public IEnumerable<string>? AuthorUrls { get; set; }
 
         /// <summary>
         /// 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 canonical name of the genre. Only one of the following names is allowed Adventure, Children's Fiction, Drama, Erotica, Essays, Fantasy, Gay &amp; Lesbian, Graphic Novels, Historical Fiction, Horror, Fiction &amp; Literature, Mystery, Mythology &amp; Folklore, Poetry, Religious &amp; Inspiratonal, Rhetoric &amp; Critcism, Romance, Satire &amp; Humor, Science Fiction, Thrillers &amp; Suspense, Westerns, Women&#039;s Fiction, Young Adult Fiction, Biography &amp; Memoir, Current Affairs &amp; Politics, Genealogy, Geography, History, History of the Ancient World, History of Africa, History of Asia, History of Europe, History of North America, History of South America, Travel, Bibliographies, Children&#039;s Non-fiction, Computer Science, Encyclopedias, General Collections, Gift Books, Information Sciences, Journalism &amp; Publishing, Magazines &amp; Journals, Manuscripts &amp; Rare Books, Epistemology, Ethics, Logic, Metaphysics, Philosophy, Parapsychology &amp; Occultism, Psychology, Self-help, Bible, Comparative Religions, Natural Theory, Theology, Business, Customs &amp; Etiquette, Economics, Education, Finance, Gay &amp; Lesbian Non-Fiction, Gender Studies, Law, Political Science, Social Sciences, Social Services, Statistics, True Crime, English &amp; Old English, French, German, Greek, Italian, Language, Latin, Linguistics, Other Languages, Portugese, Spanish, Astronomy, Chemistry, Earth Sciences, Life Sciences, Mathematics, Paleontology &amp; Paleozoology, Physics, Plants Sciences, Zoology, Agriculture, Chemical Engineering, Engineering &amp; Opera?ons, Management, Manufacturing, Medical Sciences, Technology, Cooking &amp; Cookbooks, Gardening, Home Decorating, Home Economics, Parenting, Pets, Architecture, Design, Drawing, Fine Art, Gardening, Graphic Art, Music, Painting, Performing Arts, Photography, Sculpture, Games, Fitness, Health and Sports.
         /// </summary>
         [HtmlAttributeName(CanonicalNameAttributeName)]
-        public string CanonicalName { get; set; }
+        public string? CanonicalName { get; set; }
 
         /// <summary>
         /// Gets the namespace of this open graph type.

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

@@ -28,13 +28,13 @@ public class OpenGraphBusiness : OpenGraphMetadata
         /// Gets or sets the contact data for the business.
         /// </summary>
         [HtmlAttributeName(ContactDataAttributeName)]
-        public OpenGraphContactData ContactData { get; set; }
+        public OpenGraphContactData? ContactData { get; set; }
 
         /// <summary>
         /// Gets or sets the location of the business.
         /// </summary>
         [HtmlAttributeName(LocationAttributeName)]
-        public OpenGraphLocation Location { get; set; }
+        public OpenGraphLocation? Location { get; set; }
 
         /// <summary>
         /// Gets the namespace of this open graph type.
@@ -45,7 +45,7 @@ public class OpenGraphBusiness : OpenGraphMetadata
         /// Gets or sets the opening hours of the business.
         /// </summary>
         [HtmlAttributeName(OpeningHoursAttributeName)]
-        public IEnumerable<OpenGraphHours> OpeningHours { get; set; }
+        public IEnumerable<OpenGraphHours>? OpeningHours { get; set; }
 
         /// <summary>
         /// Gets the type of your object. Depending on the type you specify, other properties may also be required.
@@ -65,15 +65,15 @@ public override void ToString(StringBuilder stringBuilder)
 
             base.ToString(stringBuilder);
 
-            stringBuilder.AppendMetaPropertyContentIfNotNull("business:contact_data:street_address", this.ContactData.StreetAddress);
-            stringBuilder.AppendMetaPropertyContentIfNotNull("business:contact_data:locality", this.ContactData.Locality);
-            stringBuilder.AppendMetaPropertyContentIfNotNull("business:contact_data:region", this.ContactData.Region);
-            stringBuilder.AppendMetaPropertyContentIfNotNull("business:contact_data:postal_code", this.ContactData.PostalCode);
-            stringBuilder.AppendMetaPropertyContentIfNotNull("business:contact_data:country_name", this.ContactData.Country);
-            stringBuilder.AppendMetaPropertyContentIfNotNull("business:contact_data:email", this.ContactData.Email);
-            stringBuilder.AppendMetaPropertyContentIfNotNull("business:contact_data:phone_number", this.ContactData.Phone);
-            stringBuilder.AppendMetaPropertyContentIfNotNull("business:contact_data:fax_number", this.ContactData.Fax);
-            stringBuilder.AppendMetaPropertyContentIfNotNull("business:contact_data:website", this.ContactData.Website);
+            stringBuilder.AppendMetaPropertyContentIfNotNull("business:contact_data:street_address", this.ContactData?.StreetAddress);
+            stringBuilder.AppendMetaPropertyContentIfNotNull("business:contact_data:locality", this.ContactData?.Locality);
+            stringBuilder.AppendMetaPropertyContentIfNotNull("business:contact_data:region", this.ContactData?.Region);
+            stringBuilder.AppendMetaPropertyContentIfNotNull("business:contact_data:postal_code", this.ContactData?.PostalCode);
+            stringBuilder.AppendMetaPropertyContentIfNotNull("business:contact_data:country_name", this.ContactData?.Country);
+            stringBuilder.AppendMetaPropertyContentIfNotNull("business:contact_data:email", this.ContactData?.Email);
+            stringBuilder.AppendMetaPropertyContentIfNotNull("business:contact_data:phone_number", this.ContactData?.Phone);
+            stringBuilder.AppendMetaPropertyContentIfNotNull("business:contact_data:fax_number", this.ContactData?.Fax);
+            stringBuilder.AppendMetaPropertyContentIfNotNull("business:contact_data:website", this.ContactData?.Website);
 
             if (this.OpeningHours is not null)
             {
@@ -85,9 +85,9 @@ public override void ToString(StringBuilder stringBuilder)
                 }
             }
 
-            stringBuilder.AppendMetaPropertyContent("place:location:latitude", this.Location.Latitude);
-            stringBuilder.AppendMetaPropertyContent("place:location:longitude", this.Location.Longitude);
-            stringBuilder.AppendMetaPropertyContentIfNotNull("place:location:altitude", this.Location.Altitude);
+            stringBuilder.AppendMetaPropertyContent("place:location:latitude", this.Location?.Latitude);
+            stringBuilder.AppendMetaPropertyContent("place:location:longitude", this.Location?.Longitude);
+            stringBuilder.AppendMetaPropertyContentIfNotNull("place:location:altitude", this.Location?.Altitude);
         }
 
         /// <summary>

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

@@ -36,31 +36,31 @@ public class OpenGraphFitnessCourse : OpenGraphMetadata
         /// Gets or sets the energy used during the course.
         /// </summary>
         [HtmlAttributeName(CustomUnitEnergyAttributeName)]
-        public OpenGraphQuantity CustomUnitEnergy { get; set; }
+        public OpenGraphQuantity? CustomUnitEnergy { get; set; }
 
         /// <summary>
         /// Gets or sets the distance of the course.
         /// </summary>
         [HtmlAttributeName(DistanceAttributeName)]
-        public OpenGraphQuantity Distance { get; set; }
+        public OpenGraphQuantity? Distance { get; set; }
 
         /// <summary>
         /// Gets or sets the duration taken on the course.
         /// </summary>
         [HtmlAttributeName(DurationAttributeName)]
-        public OpenGraphQuantity Duration { get; set; }
+        public OpenGraphQuantity? Duration { get; set; }
 
         /// <summary>
         /// Gets or sets a string value displayed in stories if the associated action's end_time has not passed, such as an encouragement to friends to cheer the user on. The value is not rendered once the course has been completed.
         /// </summary>
         [HtmlAttributeName(LiveTextAttributeName)]
-        public string LiveText { get; set; }
+        public string? LiveText { get; set; }
 
         /// <summary>
         /// Gets or sets the metrics about the course.
         /// </summary>
         [HtmlAttributeName(MetricsAttributeName)]
-        public IEnumerable<OpenGraphFitnessActivityDataPoint> Metrics { get; set; }
+        public IEnumerable<OpenGraphFitnessActivityDataPoint>? Metrics { get; set; }
 
         /// <summary>
         /// Gets the namespace of this open graph type.
@@ -71,19 +71,19 @@ public class OpenGraphFitnessCourse : OpenGraphMetadata
         /// Gets or sets the pace achieved on the course.
         /// </summary>
         [HtmlAttributeName(PaceAttributeName)]
-        public OpenGraphQuantity Pace { get; set; }
+        public OpenGraphQuantity? Pace { get; set; }
 
         /// <summary>
         /// Gets or sets the split times during the course.
         /// </summary>
         [HtmlAttributeName(SplitsAttributeName)]
-        public IEnumerable<OpenGraphSplit> Splits { get; set; }
+        public IEnumerable<OpenGraphSplit>? Splits { get; set; }
 
         /// <summary>
         /// Gets or sets the speed achieved on the course.
         /// </summary>
         [HtmlAttributeName(SpeedAttributeName)]
-        public OpenGraphQuantity Speed { get; set; }
+        public OpenGraphQuantity? Speed { get; set; }
 
         /// <summary>
         /// Gets the type of your object. Depending on the type you specify, other properties may also be required.

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

@@ -23,7 +23,7 @@ public class OpenGraphPlace : OpenGraphMetadata
         /// Gets or sets the location of the place.
         /// </summary>
         [HtmlAttributeName(LocationAttributeName)]
-        public OpenGraphLocation Location { get; set; }
+        public OpenGraphLocation? Location { get; set; }
 
         /// <summary>
         /// Gets the namespace of this open graph type.
@@ -48,9 +48,9 @@ public override void ToString(StringBuilder stringBuilder)
 
             base.ToString(stringBuilder);
 
-            stringBuilder.AppendMetaPropertyContent("place:location:latitude", this.Location.Latitude);
-            stringBuilder.AppendMetaPropertyContent("place:location:longitude", this.Location.Longitude);
-            stringBuilder.AppendMetaPropertyContentIfNotNull("place:location:altitude", this.Location.Altitude);
+            stringBuilder.AppendMetaPropertyContent("place:location:latitude", this.Location?.Latitude);
+            stringBuilder.AppendMetaPropertyContent("place:location:longitude", this.Location?.Longitude);
+            stringBuilder.AppendMetaPropertyContentIfNotNull("place:location:altitude", this.Location?.Altitude);
         }
 
         /// <summary>