Multi-targeting, phase 1

Directory.Build.targets

@@ -1,8 +1,13 @@
 <Project>
     <PropertyGroup>
         <DefineConstants>$(DefineConstants)</DefineConstants>
+        <EnableWindowsTargeting>true</EnableWindowsTargeting>
+        <LangVersion>13.0</LangVersion>
     </PropertyGroup>
     <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|AnyCPU'">
         <DefineConstants>$(DefineConstants);DEBUG;TRACE</DefineConstants>
     </PropertyGroup>
+    <ItemGroup>
+        <PackageReference Include="Meziantou.Polyfill" Version="1.0.52" PrivateAssets="all" />
+    </ItemGroup>
 </Project>

Diz.Core.Interfaces/Diz.Core.Interfaces.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
     <PropertyGroup>
-        <TargetFramework>net9.0</TargetFramework>
+        <TargetFrameworks>netstandard2.0;net9.0</TargetFrameworks>
         <ImplicitUsings>enable</ImplicitUsings>
         <Nullable>enable</Nullable>
         <GenerateAssemblyInfo>true</GenerateAssemblyInfo>

Diz.Core/Diz.Core.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>net9.0</TargetFramework>
+    <TargetFrameworks>netstandard2.0;net9.0</TargetFrameworks>
     <UseWindowsForms>false</UseWindowsForms>
     <GenerateAssemblyInfo>true</GenerateAssemblyInfo>
     <RootNamespace>Diz.Core</RootNamespace>
@@ -16,16 +16,18 @@
     <PackageReference Include="JetBrains.Annotations">
       <Version>2023.3.0</Version>
     </PackageReference>
-    <PackageReference Include="JetBrains.Profiler.SelfApi" Version="2.5.0" />
+    <PackageReference Include="JetBrains.Profiler.SelfApi" Version="2.5.0" NoWarn="NU1701" />
     <PackageReference Include="LightInject">
       <Version>6.6.4</Version>
     </PackageReference>
     <PackageReference Include="SharpZipLib">
       <Version>1.4.2</Version>
     </PackageReference>
+    <PackageReference Include="System.ComponentModel.Annotations" Version="5.0.0" />
     <PackageReference Include="System.Diagnostics.Tracing">
       <Version>4.3.0</Version>
     </PackageReference>
+    <PackageReference Include="System.Reflection.Emit" Version="4.7.0" />
     <PackageReference Include="System.Text.Encoding.CodePages" Version="8.0.0" />
     <PackageReference Include="FluentValidation">
       <Version>11.9.0</Version>

Diz.Core/Polyfills.cs

@@ -0,0 +1,41 @@
+#nullable enable
+
+namespace Diz.Core
+{
+    internal static class CollectionExtensions
+    {
+#if !(NETSTANDARD2_1_OR_GREATER || NETCOREAPP2_0_OR_GREATER)
+        public static bool TryAdd<TKey, TValue>(
+            this System.Collections.Generic.IDictionary<TKey, TValue> dictionary,
+            TKey key,
+            TValue value)
+        {
+            if (dictionary is null) throw new System.ArgumentNullException(paramName: nameof(dictionary));
+            if (dictionary.ContainsKey(key)) return false;
+            dictionary.Add(key, value);
+            return true;
+        }
+#endif
+    }
+
+    internal static class PathPolyfill
+    {
+        public static bool IsPathFullyQualified(string path)
+#if NETSTANDARD2_1_OR_GREATER || NETCOREAPP2_1_OR_GREATER
+            => System.IO.Path.IsPathFullyQualified(path);
+#else // copied from https://github.com/TASEmulators/BizHawk/commit/d9069ea2cc6d36fef16cd533389fd66482aae471
+        {
+            if (/*OSTailoredCode.IsUnixHost*/!System.Runtime.InteropServices.RuntimeInformation.IsOSPlatform(System.Runtime.InteropServices.OSPlatform.Windows))
+            {
+                return /*path.StartsWith(Path.DirectorySeparatorChar)*/path is [ '/', .. ];
+            }
+            /* Windows:
+            var root = System.IO.Path.GetPathRoot(path);
+            return root.StartsWith($"{Path.DirectorySeparatorChar}{Path.DirectorySeparatorChar}")
+                || (root.Length >= 2 && root.EndsWith(Path.DirectorySeparatorChar));
+            */
+            return System.IO.Path.GetPathRoot(path) is [ '\\', '\\', .. ] or [ .., _, '\\' ];
+        }
+#endif
+    }
+}

Diz.Core/export/LogWriterSettings.cs

@@ -91,7 +91,7 @@ public string BuildFullOutputPath()
             path += "\\"; // force it to treat it as a path.
 
         // if it's absolute path, use that first, ignore base path
-        if (Path.IsPathFullyQualified(path))
+        if (PathPolyfill.IsPathFullyQualified(path))
             return path;
 
         // if it's not an absolute path, combine BaseOutputPath and FileOrFolderPath to get the final

Diz.Core/model/Annotation.cs

@@ -285,9 +285,9 @@ public string NameOverride
             set { nameOverride = value; OnPropertyChanged(); }
         }
 
-        public event PropertyChangedEventHandler? PropertyChanged;
+        public event PropertyChangedEventHandler/*?*/ PropertyChanged;
 
-        protected virtual void OnPropertyChanged([CallerMemberName] string? propertyName = null)
+        protected virtual void OnPropertyChanged([CallerMemberName] string/*?*/ propertyName = null)
         {
             PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
         }

Diz.Core/model/snes/Data.cs

@@ -56,7 +56,7 @@ public SortedDictionary<int, string> Comments
     // deserializer that handles this instead
     public Dictionary<int, IAnnotationLabel> LabelsSerialization
     {
-        get => new(Labels.Labels);
+        get => Labels.Labels.ToDictionary();
         set => Labels.SetAll(value);
     }
 

Diz.Core/serialization/ProjectFileManager.cs

@@ -153,7 +153,7 @@ private void OnPostProjectDeserialized(string filename, ProjectXmlSerializer.Roo
         var romAddCmd = addRomDataCommandCreate();
         Debug.Assert(romAddCmd != null);
 
-        romAddCmd.Root = xmlProjectSerializedRoot;
+        romAddCmd!.Root = xmlProjectSerializedRoot;
         romAddCmd.GetNextRomFileToTry = RomPromptFn;
         romAddCmd.MigrationRunner = serializer.MigrationRunner;
 

Diz.Core/serialization/xml_serializer/PostSerializeMigrations.cs

@@ -7,8 +7,8 @@ public interface IMigrationEvents
         // add migrations to hook in various places in the code as needed.
         // example: something to pre-process incoming XML text, or modify the XML deserializer before it's used
 
-        void OnLoadingBeforeAddLinkedRom(IAddRomDataCommand romAddCmd) { }
-        void OnLoadingAfterAddLinkedRom(IAddRomDataCommand romAddCmd) { }
+        void OnLoadingBeforeAddLinkedRom(IAddRomDataCommand romAddCmd);
+        void OnLoadingAfterAddLinkedRom(IAddRomDataCommand romAddCmd);
     }
 
     public interface IMigration : IMigrationEvents

Diz.Core/util/LabelSearchTerms.cs

@@ -66,7 +66,7 @@ private bool TryParseSpecialTerm(string term)
         return false;
     }
 
-    private AddressComparison? TryParseAddressComparison(string term)
+    private AddressComparison/*?*/ TryParseAddressComparison(string term)
     {
         if (term.Length < 2)
             return null;

Diz.Core/util/Util.cs

@@ -41,7 +41,7 @@ public static string GetRelativePath(string fileSpec, string? folder)
     {
         var pathUri = new Uri(fileSpec);
         // Folders must end in a slash
-        if (!string.IsNullOrEmpty(folder) && !folder.EndsWith(Path.DirectorySeparatorChar.ToString()))
+        if (!string.IsNullOrEmpty(folder) && !folder!.EndsWith(Path.DirectorySeparatorChar.ToString()))
         {
             folder += Path.DirectorySeparatorChar;
         }
@@ -450,7 +450,7 @@ public static class NotifyPropertyChangedExtensions
     /// Set a field, and if changed, dispatch any events associated with it
     /// </summary>
     /// <returns>true if we set property to a new value and dispatched events</returns>
-    public static bool SetField<T>(this INotifyPropertyChanged sender, [CanBeNull] PropertyChangedEventHandler handler, ref T field, T value, bool compareRefOnly = false, [CallerMemberName] string propertyName = null)
+    public static bool SetField<T>(this INotifyPropertyChanged sender, [CanBeNull] PropertyChangedEventHandler? handler, ref T field, T value, bool compareRefOnly = false, [CallerMemberName] string propertyName = null!)
     {
         if (FieldIsEqual(field, value, compareRefOnly)) 
             return false;
@@ -465,7 +465,7 @@ public static bool SetField<T>(this INotifyPropertyChanged sender, [CanBeNull] P
     /// Set a field, and if changed, dispatch any events associated with it
     /// </summary>
     /// <returns>true if we set property to a new value and dispatched events</returns>
-    public static bool SetField<T>(this INotifyPropertyChangedExt sender, ref T field, T value, bool compareRefOnly = false, [CallerMemberName] string propertyName = null)
+    public static bool SetField<T>(this INotifyPropertyChangedExt sender, ref T field, T value, bool compareRefOnly = false, [CallerMemberName] string propertyName = null!)
     {
         if (FieldIsEqual(field, value, compareRefOnly)) 
             return false;

Diz.Cpu.65816/Diz.Cpu.65816.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
     <PropertyGroup>
-        <TargetFramework>net9.0</TargetFramework>
+        <TargetFrameworks>netstandard2.0;net9.0</TargetFrameworks>
         <GenerateAssemblyInfo>true</GenerateAssemblyInfo>
         <RootNamespace>Diz.Cpu._65816</RootNamespace>
         <ImplicitUsings>enable</ImplicitUsings>

Diz.Cpu.65816/src/CPU65C816.cs

@@ -309,7 +309,7 @@ public override CpuInstructionDataFormatted GetInstructionData(TByteSource data,
                 }
                 else if (specialDirective.ConstantFormatOverride == CpuUtils.OperandOverride.FormatOverride.AsDecimal && operandValue1!=null)
                 {
-                    operandFinalStr1 = operandValue1.ToString();
+                    operandFinalStr1 = operandValue1.ToString()!;
                 }
             }
         }
@@ -727,7 +727,7 @@ private static string GenerateDisplacementString(int amountToDisplace)
         // some special cases related to +/- local labels:
 
         // is this a local label?  like "+". "-", "++", "--", etc?
-        if (!RomUtil.IsValidPlusMinusLabel(candidateLabel.Name)) 
+        if (!RomUtil.IsValidPlusMinusLabel(candidateLabel!.Name))
             return candidateLabel;      // not local label, so we're good
 
         // this IS a local +/- label, so let's do some additional validation..

Diz.Cpu.65816/src/CpuUtils.cs

@@ -40,7 +40,7 @@ public enum FormatOverride
     {
         // TODO: allow multiple directives in a line separated by delimiter
 
-        if (string.IsNullOrEmpty(inputText) || !inputText.StartsWith("!!"))
+        if (string.IsNullOrEmpty(inputText) || !inputText!.StartsWith("!!"))
             return null;
 
         // filter anything after a semicolon, which we'll treat like a comment and ignore. trim leftover whitespace

Diz.Cpu.65816/src/SampleRomData.cs

@@ -278,10 +278,10 @@ private static void PostProcess(Data data)
 
         // inject the game name into the bytes
         // This is a UTF8 string that needs to be converted to ShiftJIS (Ascii w/some japanese chars) encoding.
-        snesApi.SetCartridgeTitle(GetSampleUtf8CartridgeTitle());
+        snesApi!.SetCartridgeTitle(GetSampleUtf8CartridgeTitle());
 
         // initialize some SNES header stuff (this is not complete, feel free to add things that are useful)
-        Debug.Assert(snesApi.RomMapMode == RomMapMode.LoRom);
+        Debug.Assert(snesApi!.RomMapMode == RomMapMode.LoRom);
         Debug.Assert(snesApi.RomSpeed == RomSpeed.FastRom);
         var romSettingsOffset = RomUtil.GetRomSettingOffset(RomMapMode.LoRom);
         const int loromAndFastRom = 0x30;

Diz.Cpu.65816/src/SnesData.cs

@@ -627,10 +627,10 @@ public IProject Create()
         var project = createNewProject.Create() as Project; // TODO: don't cast, refactor to use IProject instead
         Debug.Assert(project?.Data != null);
 
-        var snesData = project.Data.GetSnesApi();
+        var snesData = project!.Data.GetSnesApi();
         Debug.Assert(snesData != null);
 
-        snesData.CacheVerificationInfoFor(project);
+        snesData!.CacheVerificationInfoFor(project);
 
         return project;
     }

Diz.Cpu.65816/src/import/ImportUtils.cs

@@ -25,7 +25,7 @@ public Project Read()
 
         Debug.Assert(project?.Data != null);
 
-        project.AttachedRomFilename = importSettings.RomFilename;
+        project!.AttachedRomFilename = importSettings.RomFilename;
         project.Session = new ProjectSession(project, "")
         {
             UnsavedChanges = true
@@ -39,7 +39,7 @@ public Project Read()
         project.Data.PopulateFrom(importSettings.RomBytes, importSettings.RomMapMode, importSettings.RomSpeed);
 #else
         // old way
-        snesApi.RomMapMode = importSettings.RomMapMode;
+        snesApi!.RomMapMode = importSettings.RomMapMode;
         snesApi.RomSpeed = importSettings.RomSpeed;
         project.Data.RomBytes.CreateRomBytesFromRom(importSettings.RomBytes);
 #endif

Diz.Cpu.65816/src/import/MigrationNoOp.cs

@@ -1,4 +1,5 @@
-using Diz.Core.serialization.xml_serializer;
+using Diz.Core.serialization;
+using Diz.Core.serialization.xml_serializer;
 using JetBrains.Annotations;
 
 namespace Diz.Cpu._65816.import;
@@ -13,4 +14,8 @@ public sealed class MigrationNoOp : IMigration
 {
     // you MUST set this when instantiating though
     public int AppliesToSaveVersion { get; init; } = -1;
+
+    public void OnLoadingBeforeAddLinkedRom(IAddRomDataCommand romAddCmd) {}
+
+    public void OnLoadingAfterAddLinkedRom(IAddRomDataCommand romAddCmd) {}
 }

Diz.Import/src/bsnes/tracelog/BSNESImportStreamProcessor.cs

@@ -135,6 +135,8 @@ public IEnumerable<WorkItemDecompressSnesTraces> GetCompressedWorkItems(Stream?
 
     private WorkItemDecompressSnesTraces? ReadPacketFromStream(Stream? stream)
     {
+        if (stream is null) throw new ArgumentNullException(paramName: nameof(stream));
+
         #if PROFILING
         var mainSpan = Markers.EnterSpan("BSNES socket read");
         #endif

Diz.Ui.Eto/DizEtoAppSettingsProvider.cs

@@ -10,7 +10,7 @@ namespace Diz.Ui.Eto;
 public class DizEtoAppSettingsProvider : IDizAppSettings
 {
     public event PropertyChangedEventHandler? PropertyChanged;
-    public string LastProjectFilename { get; set; }
+    public string? LastProjectFilename { get; set; }
     public bool OpenLastFileAutomatically { get; set; }
-    public string LastOpenedFile { get; set; }
+    public string? LastOpenedFile { get; set; }
 }

Diz.Ui.Eto/ui/EtoMainGridForm.cs

@@ -95,7 +95,7 @@ private void CreateMenu()
         };
     }
 
-    private GridView gridView;
+    private GridView gridView = null!;
 
     private void CreateGui()
     {
@@ -277,7 +277,7 @@ public void SelectOffsetWithOvershoot(int pcOffset, int overshootAmount = 0)
 
     public int SelectedOffset => -1; // temp, fixme.
 
-    public Project Project { get; set; }
+    public Project? Project { get; set; }
 
     public void OnProjectOpenFail(string errorMsg)
     {

Diz.Ui.Eto/ui/EtoProgressForm.cs

@@ -7,7 +7,7 @@ namespace Diz.Ui.Eto.ui;
 public class EtoProgressForm : Dialog, IProgressView
 {
     public event EventHandler? OnFormClosed;
-    private Label mainText;
+    private Label mainText = null!;
 
     public EtoProgressForm()
     {