Use ResXFileRef from this project. Fixes #5

Test we can read file refs that we write.

Also move type data string to ResXConstants

Demonstate writing winforms assembly for internal ResXFileRef

Move winforms type conversion to library internals

Test user-provided type converters don't break winforms overwrites

Fix NullReferenceException on non-Windows platforms.

Use an ordinal comparison for type names.

Fix tests.

Switch back to C# 7.3.

Use a StringWriter instead of a temp file.

Remove local fix for tests that breaks the build.

System.Resources.NetStandard/ResXDataNode.cs

@@ -47,13 +47,13 @@ public sealed class ResXDataNode : ISerializable
         // No public property to force using constructors for the following reasons:
         // 1. one of the constructors needs this field (if used) to initialize the object, make it consistent with the other ctrs to avoid errors.
         // 2. once the object is constructed the delegate should not be changed to avoid getting inconsistent results.
-        private Func<Type, string> typeNameConverter;
+        private Func<Type, string> typeNameConverter = WinformsTypeMappers.InterceptWinformsTypes(null);
 
         private ResXDataNode()
         {
         }
 
-        internal ResXDataNode DeepClone()
+        public ResXDataNode DeepClone()
         {
             return new ResXDataNode
             {
@@ -87,7 +87,7 @@ public ResXDataNode(string name, object value, Func<Type, string> typeNameConver
                 throw (new ArgumentException(nameof(name)));
             }
 
-            this.typeNameConverter = typeNameConverter;
+            this.typeNameConverter = WinformsTypeMappers.InterceptWinformsTypes(typeNameConverter);
 
             Type valueType = (value == null) ? typeof(object) : value.GetType();
             if (value != null && !valueType.IsSerializable)
@@ -116,7 +116,7 @@ public ResXDataNode(string name, ResXFileRef fileRef, Func<Type, string> typeNam
 
             this.name = name;
             this.fileRef = fileRef ?? throw new ArgumentNullException(nameof(fileRef));
-            this.typeNameConverter = typeNameConverter;
+            this.typeNameConverter = WinformsTypeMappers.InterceptWinformsTypes(typeNameConverter);
         }
 
         internal ResXDataNode(DataNodeInfo nodeInfo, string basePath)
@@ -864,8 +864,8 @@ internal class AssemblyNamesTypeResolutionService : ITypeResolutionService
         private Hashtable cachedAssemblies;
         private Hashtable cachedTypes;
 
-        private static readonly string s_dotNetPath = Path.Combine(Environment.GetEnvironmentVariable("ProgramFiles"), "dotnet\\shared");
-        private static readonly string s_dotNetPathX86 = Path.Combine(Environment.GetEnvironmentVariable("ProgramFiles(x86)"), "dotnet\\shared");
+        private static readonly string s_dotNetPath = Environment.GetEnvironmentVariable("ProgramFiles") != null ? Path.Combine(Environment.GetEnvironmentVariable("ProgramFiles"), "dotnet", "shared") : null;
+        private static readonly string s_dotNetPathX86 = Environment.GetEnvironmentVariable("ProgramFiles(x86)") != null ? Path.Combine(Environment.GetEnvironmentVariable("ProgramFiles(x86)"), "dotnet", "shared") : null;
 
         internal AssemblyNamesTypeResolutionService(AssemblyName[] names)
         {
@@ -956,6 +956,13 @@ public Type GetType(string name, bool throwOnError, bool ignoreCase)
                 return result;
             }
 
+            // Replace the WinForms ResXFileRef with the copy in this library
+            if (name.StartsWith(ResXConstants.ResxFileRef_TypeNameAndAssembly, StringComparison.Ordinal))
+            {
+                result = typeof(ResXFileRef);
+                return result;
+            }
+
             // Missed in cache, try to resolve the type from the reference assemblies.
             if (name.IndexOf(',') != -1)
             {
@@ -1047,7 +1054,7 @@ public Type GetType(string name, bool throwOnError, bool ignoreCase)
         /// </summary>
         private bool IsDotNetAssembly(string assemblyPath)
         {
-            return assemblyPath != null && (assemblyPath.StartsWith(s_dotNetPath, StringComparison.OrdinalIgnoreCase) || assemblyPath.StartsWith(s_dotNetPathX86, StringComparison.OrdinalIgnoreCase));
+            return assemblyPath != null && s_dotNetPath != null && (assemblyPath.StartsWith(s_dotNetPath, StringComparison.OrdinalIgnoreCase) || assemblyPath.StartsWith(s_dotNetPathX86, StringComparison.OrdinalIgnoreCase));
         }
 
         public void ReferenceAssembly(AssemblyName name)

System.Resources.NetStandard/ResXResourceWriter.cs

@@ -102,7 +102,7 @@ public class ResXResourceWriter : IResourceWriter
         bool hasBeenSaved;
         bool initialized;
 
-        private readonly Func<Type, string> typeNameConverter; // no public property to be consistent with ResXDataNode class.
+        private readonly Func<Type, string> typeNameConverter = WinformsTypeMappers.InterceptWinformsTypes(null); // no public property to be consistent with ResXDataNode class.
 
         /// <summary>
         ///  Base Path for ResXFileRefs.
@@ -119,7 +119,7 @@ public ResXResourceWriter(string fileName)
         public ResXResourceWriter(string fileName, Func<Type, string> typeNameConverter)
         {
             this.fileName = fileName;
-            this.typeNameConverter = typeNameConverter;
+            this.typeNameConverter = WinformsTypeMappers.InterceptWinformsTypes(typeNameConverter);
         }
 
         /// <summary>
@@ -132,7 +132,7 @@ public ResXResourceWriter(Stream stream)
         public ResXResourceWriter(Stream stream, Func<Type, string> typeNameConverter)
         {
             this.stream = stream;
-            this.typeNameConverter = typeNameConverter;
+            this.typeNameConverter = WinformsTypeMappers.InterceptWinformsTypes(typeNameConverter);
         }
 
         /// <summary>
@@ -145,7 +145,7 @@ public ResXResourceWriter(TextWriter textWriter)
         public ResXResourceWriter(TextWriter textWriter, Func<Type, string> typeNameConverter)
         {
             this.textWriter = textWriter;
-            this.typeNameConverter = typeNameConverter;
+            this.typeNameConverter = WinformsTypeMappers.InterceptWinformsTypes(typeNameConverter);
         }
 
         ~ResXResourceWriter()

System.Resources.NetStandard/ResxConstants.cs

@@ -6,5 +6,9 @@ internal class ResXConstants
 
         public static string ResHeaderReaderTypeName => ResHeaderReader.Split(',')[0].Trim();
         public static string ResHeaderWriterTypeName => ResHeaderWriter.Split(',')[0].Trim();
+
+
+        public const string ResxFileRefTypeInfo = "System.Resources.ResXFileRef, System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089";
+        public const string ResxFileRef_TypeNameAndAssembly = "System.Resources.ResXFileRef, System.Windows.Forms";
     }
 }

System.Resources.NetStandard/WinformsTypeMappers.cs

@@ -0,0 +1,26 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace System.Resources.NetStandard
+{
+    internal static class WinformsTypeMappers
+    {
+        public static Func<Type, string> InterceptWinformsTypes(Func<Type,string> typeNameConverter)
+        {
+            return (Type type) =>
+            {
+                if (type.AssemblyQualifiedName == typeof(ResXFileRef).AssemblyQualifiedName)
+                {
+                    return NetStandard.ResXConstants.ResxFileRefTypeInfo;
+                }
+                else
+                {
+                    if (typeNameConverter != null) return typeNameConverter(type);
+                    else return null;
+                }
+            };
+        }
+
+    }
+}