From 279e3a479d79eeaf2d912abe205f54c10960d9fa Mon Sep 17 00:00:00 2001
From: Adrian Kokot <35179235+AdrianKokot@users.noreply.github.com>
Date: Tue, 5 Mar 2024 16:17:16 +0100
Subject: [PATCH] Fix ResXNullRef type handling (#10)

* Fix ResXNullRef type handling

* Clarify the exclusivity of cases in winforms type mapping

* Test vs editor compatibility for ResXNullRef node writes

Also fixed a misunderstanding in the round trip test

---------

Co-authored-by: Spencer Farley <2847259+farlee2121@users.noreply.github.com>
---
 System.Resources.NetStandard/ResXDataNode.cs  |  19 +-
 System.Resources.NetStandard/ResxConstants.cs |   3 +
 .../WinformsTypeMappers.cs                    |  15 +-
 Tests/Example.Designer.cs                     | 265 +++++++++--------
 Tests/Example.resx                            | 273 +++++++++---------
 Tests/ResxDataNodeTests.cs                    |  93 +++++-
 Tests/ResxWithNullRef.resx                    |  65 +++++
 Tests/System.Resources.Tests.csproj           |   4 +
 8 files changed, 465 insertions(+), 272 deletions(-)
 create mode 100644 Tests/ResxWithNullRef.resx

diff --git a/System.Resources.NetStandard/ResXDataNode.cs b/System.Resources.NetStandard/ResXDataNode.cs
index 1cb93d8..3398191 100644
--- a/System.Resources.NetStandard/ResXDataNode.cs
+++ b/System.Resources.NetStandard/ResXDataNode.cs
@@ -158,6 +158,11 @@ private void InitializeDataNode(string basePath)
                     }
                 }
             }
+
+            if (nodeType != null && nodeType.Equals(typeof(ResXNullRef)))
+            {
+                value = new ResXNullRef();
+            }
         }
 
         /// <summary>
@@ -619,11 +624,16 @@ public string GetValueTypeName(AssemblyName[] names)
         /// </summary>
         public object GetValue(ITypeResolutionService typeResolver)
         {
+            if (value is ResXNullRef)
+            {
+                return null;
+            }
+            
             if (value != null)
             {
                 return value;
             }
-
+            
             object result = null;
             if (FileRefFullPath != null)
             {
@@ -962,6 +972,13 @@ public Type GetType(string name, bool throwOnError, bool ignoreCase)
                 result = typeof(ResXFileRef);
                 return result;
             }
+            
+            // Replace the WinForms ResXNullRef with the copy in this library
+            if (name.StartsWith(ResXConstants.ResXNullRef_TypeNameAndAssembly, StringComparison.Ordinal))
+            {
+                result = typeof(ResXNullRef);
+                return result;
+            }
 
             // Missed in cache, try to resolve the type from the reference assemblies.
             if (name.IndexOf(',') != -1)
diff --git a/System.Resources.NetStandard/ResxConstants.cs b/System.Resources.NetStandard/ResxConstants.cs
index 6274ed7..73720dd 100644
--- a/System.Resources.NetStandard/ResxConstants.cs
+++ b/System.Resources.NetStandard/ResxConstants.cs
@@ -10,5 +10,8 @@ internal class ResXConstants
 
         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";
+        
+        public const string ResxNullRefTypeInfo = "System.Resources.ResXNullRef, System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089";
+        public const string ResXNullRef_TypeNameAndAssembly = "System.Resources.ResXNullRef, System.Windows.Forms";
     }
 }
\ No newline at end of file
diff --git a/System.Resources.NetStandard/WinformsTypeMappers.cs b/System.Resources.NetStandard/WinformsTypeMappers.cs
index 235a94e..b30380c 100644
--- a/System.Resources.NetStandard/WinformsTypeMappers.cs
+++ b/System.Resources.NetStandard/WinformsTypeMappers.cs
@@ -1,8 +1,4 @@
-using System;
-using System.Collections.Generic;
-using System.Text;
-
-namespace System.Resources.NetStandard
+namespace System.Resources.NetStandard
 {
     internal static class WinformsTypeMappers
     {
@@ -12,13 +8,14 @@ public static Func<Type, string> InterceptWinformsTypes(Func<Type,string> typeNa
             {
                 if (type.AssemblyQualifiedName == typeof(ResXFileRef).AssemblyQualifiedName)
                 {
-                    return NetStandard.ResXConstants.ResxFileRefTypeInfo;
+                    return ResXConstants.ResxFileRefTypeInfo;
                 }
-                else
+                else if (type.AssemblyQualifiedName == typeof(ResXNullRef).AssemblyQualifiedName)
                 {
-                    if (typeNameConverter != null) return typeNameConverter(type);
-                    else return null;
+                    return ResXConstants.ResxNullRefTypeInfo;
                 }
+                else if (typeNameConverter != null) return typeNameConverter(type);
+                else return null;
             };
         }
         
diff --git a/Tests/Example.Designer.cs b/Tests/Example.Designer.cs
index 3222955..3f12d7b 100644
--- a/Tests/Example.Designer.cs
+++ b/Tests/Example.Designer.cs
@@ -1,123 +1,142 @@
-//------------------------------------------------------------------------------
-// <auto-generated>
-//     This code was generated by a tool.
-//     Runtime Version:4.0.30319.42000
-//
-//     Changes to this file may cause incorrect behavior and will be lost if
-//     the code is regenerated.
-// </auto-generated>
-//------------------------------------------------------------------------------
-
-namespace System.Resources.Tests {
-    using System;
-    
-    
-    /// <summary>
-    ///   A strongly-typed resource class, for looking up localized strings, etc.
-    /// </summary>
-    // This class was auto-generated by the StronglyTypedResourceBuilder
-    // class via a tool like ResGen or Visual Studio.
-    // To add or remove a member, edit your .ResX file then rerun ResGen
-    // with the /str option, or rebuild your VS project.
-    [global::System.CodeDom.Compiler.GeneratedCodeAttribute("System.Resources.Tools.StronglyTypedResourceBuilder", "17.0.0.0")]
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute()]
-    [global::System.Runtime.CompilerServices.CompilerGeneratedAttribute()]
-    internal class Example {
-        
-        private static global::System.Resources.ResourceManager resourceMan;
-        
-        private static global::System.Globalization.CultureInfo resourceCulture;
-        
-        [global::System.Diagnostics.CodeAnalysis.SuppressMessageAttribute("Microsoft.Performance", "CA1811:AvoidUncalledPrivateCode")]
-        internal Example() {
-        }
-        
-        /// <summary>
-        ///   Returns the cached ResourceManager instance used by this class.
-        /// </summary>
-        [global::System.ComponentModel.EditorBrowsableAttribute(global::System.ComponentModel.EditorBrowsableState.Advanced)]
-        internal static global::System.Resources.ResourceManager ResourceManager {
-            get {
-                if (object.ReferenceEquals(resourceMan, null)) {
-                    global::System.Resources.ResourceManager temp = new global::System.Resources.ResourceManager("System.Resources.Tests.Example", typeof(Example).Assembly);
-                    resourceMan = temp;
-                }
-                return resourceMan;
-            }
-        }
-        
-        /// <summary>
-        ///   Overrides the current thread's CurrentUICulture property for all
-        ///   resource lookups using this strongly typed resource class.
-        /// </summary>
-        [global::System.ComponentModel.EditorBrowsableAttribute(global::System.ComponentModel.EditorBrowsableState.Advanced)]
-        internal static global::System.Globalization.CultureInfo Culture {
-            get {
-                return resourceCulture;
-            }
-            set {
-                resourceCulture = value;
-            }
-        }
-        
-        /// <summary>
-        ///   Looks up a localized resource of type System.Drawing.Icon similar to (Icon).
-        /// </summary>
-        internal static System.Drawing.Icon Error {
-            get {
-                object obj = ResourceManager.GetObject("Error", resourceCulture);
-                return ((System.Drawing.Icon)(obj));
-            }
-        }
-        
-        /// <summary>
-        ///   Looks up a localized resource of type System.Drawing.Bitmap.
-        /// </summary>
-        internal static System.Drawing.Bitmap ErrorControl {
-            get {
-                object obj = ResourceManager.GetObject("ErrorControl", resourceCulture);
-                return ((System.Drawing.Bitmap)(obj));
-            }
-        }
-        
-        /// <summary>
-        ///   Looks up a localized string similar to &lt;?xml version=&quot;1.0&quot; encoding=&quot;utf-8&quot; ?&gt;
-        ///&lt;Root&gt;
-        ///    &lt;Element&gt;Text&lt;/Element&gt;
-        ///&lt;/Root&gt;.
-        /// </summary>
-        internal static string FileRef {
-            get {
-                return ResourceManager.GetString("FileRef", resourceCulture);
-            }
-        }
-        
-        /// <summary>
-        ///   Looks up a localized string similar to &lt;?xml version=&quot;1.0&quot; encoding=&quot;utf-8&quot;?&gt;
-        ///&lt;root&gt;
-        ///  &lt;xsd:schema id=&quot;root&quot; xmlns=&quot;&quot; xmlns:xsd=&quot;http://www.w3.org/2001/XMLSchema&quot; xmlns:msdata=&quot;urn:schemas-microsoft-com:xml-msdata&quot;&gt;
-        ///    &lt;xsd:import namespace=&quot;http://www.w3.org/XML/1998/namespace&quot; /&gt;
-        ///    &lt;xsd:element name=&quot;root&quot; msdata:IsDataSet=&quot;true&quot;&gt;
-        ///      &lt;xsd:complexType&gt;
-        ///        &lt;xsd:choice maxOccurs=&quot;unbounded&quot;&gt;
-        ///          &lt;xsd:element name=&quot;metadata&quot;&gt;
-        ///            &lt;xsd:complexType&gt;
-        ///              &lt;xsd:sequence&gt;
-        ///                &lt;xsd:element name=&quot;va [rest of string was truncated]&quot;;.
-        /// </summary>
-        internal static string ResxWithFileRef {
-            get {
-                return ResourceManager.GetString("ResxWithFileRef", resourceCulture);
-            }
-        }
-        
-        /// <summary>
-        ///   Looks up a localized string similar to Text.
-        /// </summary>
-        internal static string text_ansi {
-            get {
-                return ResourceManager.GetString("text_ansi", resourceCulture);
-            }
-        }
-    }
-}
+//------------------------------------------------------------------------------
+// <auto-generated>
+//     This code was generated by a tool.
+//     Runtime Version:4.0.30319.42000
+//
+//     Changes to this file may cause incorrect behavior and will be lost if
+//     the code is regenerated.
+// </auto-generated>
+//------------------------------------------------------------------------------
+
+namespace System.Resources.Tests {
+    using System;
+    
+    
+    /// <summary>
+    ///   A strongly-typed resource class, for looking up localized strings, etc.
+    /// </summary>
+    // This class was auto-generated by the StronglyTypedResourceBuilder
+    // class via a tool like ResGen or Visual Studio.
+    // To add or remove a member, edit your .ResX file then rerun ResGen
+    // with the /str option, or rebuild your VS project.
+    [global::System.CodeDom.Compiler.GeneratedCodeAttribute("System.Resources.Tools.StronglyTypedResourceBuilder", "17.0.0.0")]
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute()]
+    [global::System.Runtime.CompilerServices.CompilerGeneratedAttribute()]
+    internal class Example {
+        
+        private static global::System.Resources.ResourceManager resourceMan;
+        
+        private static global::System.Globalization.CultureInfo resourceCulture;
+        
+        [global::System.Diagnostics.CodeAnalysis.SuppressMessageAttribute("Microsoft.Performance", "CA1811:AvoidUncalledPrivateCode")]
+        internal Example() {
+        }
+        
+        /// <summary>
+        ///   Returns the cached ResourceManager instance used by this class.
+        /// </summary>
+        [global::System.ComponentModel.EditorBrowsableAttribute(global::System.ComponentModel.EditorBrowsableState.Advanced)]
+        internal static global::System.Resources.ResourceManager ResourceManager {
+            get {
+                if (object.ReferenceEquals(resourceMan, null)) {
+                    global::System.Resources.ResourceManager temp = new global::System.Resources.ResourceManager("System.Resources.Tests.Example", typeof(Example).Assembly);
+                    resourceMan = temp;
+                }
+                return resourceMan;
+            }
+        }
+        
+        /// <summary>
+        ///   Overrides the current thread's CurrentUICulture property for all
+        ///   resource lookups using this strongly typed resource class.
+        /// </summary>
+        [global::System.ComponentModel.EditorBrowsableAttribute(global::System.ComponentModel.EditorBrowsableState.Advanced)]
+        internal static global::System.Globalization.CultureInfo Culture {
+            get {
+                return resourceCulture;
+            }
+            set {
+                resourceCulture = value;
+            }
+        }
+        
+        /// <summary>
+        ///   Looks up a localized resource of type System.Drawing.Icon similar to (Icon).
+        /// </summary>
+        internal static System.Drawing.Icon Error {
+            get {
+                object obj = ResourceManager.GetObject("Error", resourceCulture);
+                return ((System.Drawing.Icon)(obj));
+            }
+        }
+        
+        /// <summary>
+        ///   Looks up a localized resource of type System.Drawing.Bitmap.
+        /// </summary>
+        internal static System.Drawing.Bitmap ErrorControl {
+            get {
+                object obj = ResourceManager.GetObject("ErrorControl", resourceCulture);
+                return ((System.Drawing.Bitmap)(obj));
+            }
+        }
+        
+        /// <summary>
+        ///   Looks up a localized string similar to &lt;?xml version=&quot;1.0&quot; encoding=&quot;utf-8&quot; ?&gt;
+        ///&lt;Root&gt;
+        ///    &lt;Element&gt;Text&lt;/Element&gt;
+        ///&lt;/Root&gt;.
+        /// </summary>
+        internal static string FileRef {
+            get {
+                return ResourceManager.GetString("FileRef", resourceCulture);
+            }
+        }
+        
+        /// <summary>
+        ///   Looks up a localized string similar to &lt;?xml version=&quot;1.0&quot; encoding=&quot;utf-8&quot;?&gt;
+        ///&lt;root&gt;
+        ///  &lt;xsd:schema id=&quot;root&quot; xmlns=&quot;&quot; xmlns:xsd=&quot;http://www.w3.org/2001/XMLSchema&quot; xmlns:msdata=&quot;urn:schemas-microsoft-com:xml-msdata&quot;&gt;
+        ///    &lt;xsd:import namespace=&quot;http://www.w3.org/XML/1998/namespace&quot; /&gt;
+        ///    &lt;xsd:element name=&quot;root&quot; msdata:IsDataSet=&quot;true&quot;&gt;
+        ///      &lt;xsd:complexType&gt;
+        ///        &lt;xsd:choice maxOccurs=&quot;unbounded&quot;&gt;
+        ///          &lt;xsd:element name=&quot;metadata&quot;&gt;
+        ///            &lt;xsd:complexType&gt;
+        ///              &lt;xsd:sequence&gt;
+        ///                &lt;xsd:element name=&quot;va [rest of string was truncated]&quot;;.
+        /// </summary>
+        internal static string ResxWithFileRef {
+            get {
+                return ResourceManager.GetString("ResxWithFileRef", resourceCulture);
+            }
+        }
+        
+        /// <summary>
+        ///   Looks up a localized string similar to &lt;?xml version=&quot;1.0&quot; encoding=&quot;utf-8&quot;?&gt;
+        ///&lt;root&gt;
+        ///  &lt;xsd:schema id=&quot;root&quot; xmlns=&quot;&quot; xmlns:xsd=&quot;http://www.w3.org/2001/XMLSchema&quot; xmlns:msdata=&quot;urn:schemas-microsoft-com:xml-msdata&quot;&gt;
+        ///    &lt;xsd:import namespace=&quot;http://www.w3.org/XML/1998/namespace&quot; /&gt;
+        ///    &lt;xsd:element name=&quot;root&quot; msdata:IsDataSet=&quot;true&quot;&gt;
+        ///      &lt;xsd:complexType&gt;
+        ///        &lt;xsd:choice maxOccurs=&quot;unbounded&quot;&gt;
+        ///          &lt;xsd:element name=&quot;metadata&quot;&gt;
+        ///            &lt;xsd:complexType&gt;
+        ///              &lt;xsd:sequence&gt;
+        ///                &lt;xsd:element name=&quot;va [rest of string was truncated]&quot;;.
+        /// </summary>
+        internal static string ResxWithNullRef {
+            get {
+                return ResourceManager.GetString("ResxWithNullRef", resourceCulture);
+            }
+        }
+        
+        /// <summary>
+        ///   Looks up a localized string similar to Text.
+        /// </summary>
+        internal static string text_ansi {
+            get {
+                return ResourceManager.GetString("text_ansi", resourceCulture);
+            }
+        }
+    }
+}
diff --git a/Tests/Example.resx b/Tests/Example.resx
index e74bc50..0d40358 100644
--- a/Tests/Example.resx
+++ b/Tests/Example.resx
@@ -1,136 +1,139 @@
-<?xml version="1.0" encoding="utf-8"?>
-<root>
-  <!-- 
-    Microsoft ResX Schema 
-    
-    Version 2.0
-    
-    The primary goals of this format is to allow a simple XML format 
-    that is mostly human readable. The generation and parsing of the 
-    various data types are done through the TypeConverter classes 
-    associated with the data types.
-    
-    Example:
-    
-    ... ado.net/XML headers & schema ...
-    <resheader name="resmimetype">text/microsoft-resx</resheader>
-    <resheader name="version">2.0</resheader>
-    <resheader name="reader">System.Resources.ResXResourceReader, System.Windows.Forms, ...</resheader>
-    <resheader name="writer">System.Resources.ResXResourceWriter, System.Windows.Forms, ...</resheader>
-    <data name="Name1"><value>this is my long string</value><comment>this is a comment</comment></data>
-    <data name="Color1" type="System.Drawing.Color, System.Drawing">Blue</data>
-    <data name="Bitmap1" mimetype="application/x-microsoft.net.object.binary.base64">
-        <value>[base64 mime encoded serialized .NET Framework object]</value>
-    </data>
-    <data name="Icon1" type="System.Drawing.Icon, System.Drawing" mimetype="application/x-microsoft.net.object.bytearray.base64">
-        <value>[base64 mime encoded string representing a byte array form of the .NET Framework object]</value>
-        <comment>This is a comment</comment>
-    </data>
-                
-    There are any number of "resheader" rows that contain simple 
-    name/value pairs.
-    
-    Each data row contains a name, and value. The row also contains a 
-    type or mimetype. Type corresponds to a .NET class that support 
-    text/value conversion through the TypeConverter architecture. 
-    Classes that don't support this are serialized and stored with the 
-    mimetype set.
-    
-    The mimetype is used for serialized objects, and tells the 
-    ResXResourceReader how to depersist the object. This is currently not 
-    extensible. For a given mimetype the value must be set accordingly:
-    
-    Note - application/x-microsoft.net.object.binary.base64 is the format 
-    that the ResXResourceWriter will generate, however the reader can 
-    read any of the formats listed below.
-    
-    mimetype: application/x-microsoft.net.object.binary.base64
-    value   : The object must be serialized with 
-            : System.Runtime.Serialization.Formatters.Binary.BinaryFormatter
-            : and then encoded with base64 encoding.
-    
-    mimetype: application/x-microsoft.net.object.soap.base64
-    value   : The object must be serialized with 
-            : System.Runtime.Serialization.Formatters.Soap.SoapFormatter
-            : and then encoded with base64 encoding.
-
-    mimetype: application/x-microsoft.net.object.bytearray.base64
-    value   : The object must be serialized into a byte array 
-            : using a System.ComponentModel.TypeConverter
-            : and then encoded with base64 encoding.
-    -->
-  <xsd:schema id="root" xmlns="" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:msdata="urn:schemas-microsoft-com:xml-msdata">
-    <xsd:import namespace="http://www.w3.org/XML/1998/namespace" />
-    <xsd:element name="root" msdata:IsDataSet="true">
-      <xsd:complexType>
-        <xsd:choice maxOccurs="unbounded">
-          <xsd:element name="metadata">
-            <xsd:complexType>
-              <xsd:sequence>
-                <xsd:element name="value" type="xsd:string" minOccurs="0" />
-              </xsd:sequence>
-              <xsd:attribute name="name" use="required" type="xsd:string" />
-              <xsd:attribute name="type" type="xsd:string" />
-              <xsd:attribute name="mimetype" type="xsd:string" />
-              <xsd:attribute ref="xml:space" />
-            </xsd:complexType>
-          </xsd:element>
-          <xsd:element name="assembly">
-            <xsd:complexType>
-              <xsd:attribute name="alias" type="xsd:string" />
-              <xsd:attribute name="name" type="xsd:string" />
-            </xsd:complexType>
-          </xsd:element>
-          <xsd:element name="data">
-            <xsd:complexType>
-              <xsd:sequence>
-                <xsd:element name="value" type="xsd:string" minOccurs="0" msdata:Ordinal="1" />
-                <xsd:element name="comment" type="xsd:string" minOccurs="0" msdata:Ordinal="2" />
-              </xsd:sequence>
-              <xsd:attribute name="name" type="xsd:string" use="required" msdata:Ordinal="1" />
-              <xsd:attribute name="type" type="xsd:string" msdata:Ordinal="3" />
-              <xsd:attribute name="mimetype" type="xsd:string" msdata:Ordinal="4" />
-              <xsd:attribute ref="xml:space" />
-            </xsd:complexType>
-          </xsd:element>
-          <xsd:element name="resheader">
-            <xsd:complexType>
-              <xsd:sequence>
-                <xsd:element name="value" type="xsd:string" minOccurs="0" msdata:Ordinal="1" />
-              </xsd:sequence>
-              <xsd:attribute name="name" type="xsd:string" use="required" />
-            </xsd:complexType>
-          </xsd:element>
-        </xsd:choice>
-      </xsd:complexType>
-    </xsd:element>
-  </xsd:schema>
-  <resheader name="resmimetype">
-    <value>text/microsoft-resx</value>
-  </resheader>
-  <resheader name="version">
-    <value>2.0</value>
-  </resheader>
-  <resheader name="reader">
-    <value>System.Resources.ResXResourceReader, System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
-  </resheader>
-  <resheader name="writer">
-    <value>System.Resources.ResXResourceWriter, System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
-  </resheader>
-  <assembly alias="System.Windows.Forms" name="System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" />
-  <data name="Error" type="System.Resources.ResXFileRef, System.Windows.Forms">
-    <value>TestResources\Files\Error.ico;System.Drawing.Icon, System.Drawing, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a</value>
-  </data>
-  <data name="ErrorControl" type="System.Resources.ResXFileRef, System.Windows.Forms">
-    <value>TestResources\Files\ErrorControl.bmp;System.Drawing.Bitmap, System.Drawing, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a</value>
-  </data>
-  <data name="FileRef" type="System.Resources.ResXFileRef, System.Windows.Forms">
-    <value>TestResources\Files\FileRef.xml;System.String, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089;utf-8</value>
-  </data>
-  <data name="ResxWithFileRef" type="System.Resources.ResXFileRef, System.Windows.Forms">
-    <value>ResxWithFileRef.resx;System.String, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089;utf-8</value>
-  </data>
-  <data name="text_ansi" type="System.Resources.ResXFileRef, System.Windows.Forms">
-    <value>TestResources\Files\text.ansi.txt;System.String, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089;Windows-1252</value>
-  </data>
+<?xml version="1.0" encoding="utf-8"?>
+<root>
+  <!-- 
+    Microsoft ResX Schema 
+    
+    Version 2.0
+    
+    The primary goals of this format is to allow a simple XML format 
+    that is mostly human readable. The generation and parsing of the 
+    various data types are done through the TypeConverter classes 
+    associated with the data types.
+    
+    Example:
+    
+    ... ado.net/XML headers & schema ...
+    <resheader name="resmimetype">text/microsoft-resx</resheader>
+    <resheader name="version">2.0</resheader>
+    <resheader name="reader">System.Resources.ResXResourceReader, System.Windows.Forms, ...</resheader>
+    <resheader name="writer">System.Resources.ResXResourceWriter, System.Windows.Forms, ...</resheader>
+    <data name="Name1"><value>this is my long string</value><comment>this is a comment</comment></data>
+    <data name="Color1" type="System.Drawing.Color, System.Drawing">Blue</data>
+    <data name="Bitmap1" mimetype="application/x-microsoft.net.object.binary.base64">
+        <value>[base64 mime encoded serialized .NET Framework object]</value>
+    </data>
+    <data name="Icon1" type="System.Drawing.Icon, System.Drawing" mimetype="application/x-microsoft.net.object.bytearray.base64">
+        <value>[base64 mime encoded string representing a byte array form of the .NET Framework object]</value>
+        <comment>This is a comment</comment>
+    </data>
+                
+    There are any number of "resheader" rows that contain simple 
+    name/value pairs.
+    
+    Each data row contains a name, and value. The row also contains a 
+    type or mimetype. Type corresponds to a .NET class that support 
+    text/value conversion through the TypeConverter architecture. 
+    Classes that don't support this are serialized and stored with the 
+    mimetype set.
+    
+    The mimetype is used for serialized objects, and tells the 
+    ResXResourceReader how to depersist the object. This is currently not 
+    extensible. For a given mimetype the value must be set accordingly:
+    
+    Note - application/x-microsoft.net.object.binary.base64 is the format 
+    that the ResXResourceWriter will generate, however the reader can 
+    read any of the formats listed below.
+    
+    mimetype: application/x-microsoft.net.object.binary.base64
+    value   : The object must be serialized with 
+            : System.Runtime.Serialization.Formatters.Binary.BinaryFormatter
+            : and then encoded with base64 encoding.
+    
+    mimetype: application/x-microsoft.net.object.soap.base64
+    value   : The object must be serialized with 
+            : System.Runtime.Serialization.Formatters.Soap.SoapFormatter
+            : and then encoded with base64 encoding.
+
+    mimetype: application/x-microsoft.net.object.bytearray.base64
+    value   : The object must be serialized into a byte array 
+            : using a System.ComponentModel.TypeConverter
+            : and then encoded with base64 encoding.
+    -->
+  <xsd:schema id="root" xmlns="" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:msdata="urn:schemas-microsoft-com:xml-msdata">
+    <xsd:import namespace="http://www.w3.org/XML/1998/namespace" />
+    <xsd:element name="root" msdata:IsDataSet="true">
+      <xsd:complexType>
+        <xsd:choice maxOccurs="unbounded">
+          <xsd:element name="metadata">
+            <xsd:complexType>
+              <xsd:sequence>
+                <xsd:element name="value" type="xsd:string" minOccurs="0" />
+              </xsd:sequence>
+              <xsd:attribute name="name" use="required" type="xsd:string" />
+              <xsd:attribute name="type" type="xsd:string" />
+              <xsd:attribute name="mimetype" type="xsd:string" />
+              <xsd:attribute ref="xml:space" />
+            </xsd:complexType>
+          </xsd:element>
+          <xsd:element name="assembly">
+            <xsd:complexType>
+              <xsd:attribute name="alias" type="xsd:string" />
+              <xsd:attribute name="name" type="xsd:string" />
+            </xsd:complexType>
+          </xsd:element>
+          <xsd:element name="data">
+            <xsd:complexType>
+              <xsd:sequence>
+                <xsd:element name="value" type="xsd:string" minOccurs="0" msdata:Ordinal="1" />
+                <xsd:element name="comment" type="xsd:string" minOccurs="0" msdata:Ordinal="2" />
+              </xsd:sequence>
+              <xsd:attribute name="name" type="xsd:string" use="required" msdata:Ordinal="1" />
+              <xsd:attribute name="type" type="xsd:string" msdata:Ordinal="3" />
+              <xsd:attribute name="mimetype" type="xsd:string" msdata:Ordinal="4" />
+              <xsd:attribute ref="xml:space" />
+            </xsd:complexType>
+          </xsd:element>
+          <xsd:element name="resheader">
+            <xsd:complexType>
+              <xsd:sequence>
+                <xsd:element name="value" type="xsd:string" minOccurs="0" msdata:Ordinal="1" />
+              </xsd:sequence>
+              <xsd:attribute name="name" type="xsd:string" use="required" />
+            </xsd:complexType>
+          </xsd:element>
+        </xsd:choice>
+      </xsd:complexType>
+    </xsd:element>
+  </xsd:schema>
+  <resheader name="resmimetype">
+    <value>text/microsoft-resx</value>
+  </resheader>
+  <resheader name="version">
+    <value>2.0</value>
+  </resheader>
+  <resheader name="reader">
+    <value>System.Resources.ResXResourceReader, System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
+  </resheader>
+  <resheader name="writer">
+    <value>System.Resources.ResXResourceWriter, System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
+  </resheader>
+  <assembly alias="System.Windows.Forms" name="System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" />
+  <data name="Error" type="System.Resources.ResXFileRef, System.Windows.Forms">
+    <value>TestResources\Files\Error.ico;System.Drawing.Icon, System.Drawing, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a</value>
+  </data>
+  <data name="ErrorControl" type="System.Resources.ResXFileRef, System.Windows.Forms">
+    <value>TestResources\Files\ErrorControl.bmp;System.Drawing.Bitmap, System.Drawing, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a</value>
+  </data>
+  <data name="FileRef" type="System.Resources.ResXFileRef, System.Windows.Forms">
+    <value>TestResources\Files\FileRef.xml;System.String, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089;utf-8</value>
+  </data>
+  <data name="ResxWithFileRef" type="System.Resources.ResXFileRef, System.Windows.Forms">
+    <value>ResxWithFileRef.resx;System.String, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089;utf-8</value>
+  </data>
+  <data name="text_ansi" type="System.Resources.ResXFileRef, System.Windows.Forms">
+    <value>TestResources\Files\text.ansi.txt;System.String, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089;Windows-1252</value>
+  </data>
+  <data name="ResxWithNullRef" type="System.Resources.ResXFileRef, System.Windows.Forms">
+    <value>ResxWithNullRef.resx;System.String, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089;utf-8</value>
+  </data>
 </root>
\ No newline at end of file
diff --git a/Tests/ResxDataNodeTests.cs b/Tests/ResxDataNodeTests.cs
index 1e0beac..634239c 100644
--- a/Tests/ResxDataNodeTests.cs
+++ b/Tests/ResxDataNodeTests.cs
@@ -6,13 +6,10 @@
 using System.Collections;
 using System.Drawing;
 using System.Reflection;
-using System.Reflection.PortableExecutable;
 using System.Resources.Tests;
 using Xunit;
 using System.IO;
-using System.Linq;
 using System.Text;
-using System.ComponentModel.Design;
 
 namespace System.Resources.NetStandard.Tests
 {
@@ -105,7 +102,7 @@ private List<ResXDataNode> ReaderToNodes(ResXResourceReader reader)
         }
 
         [Fact]
-        public void ResxDataNode_ResXFileRefsWrittenBackWithSameAssemblyInfo()
+        public void ResxDataNode_ResXFileRefs_WrittenBackWithSameAssemblyInfo()
         {
             // This test ensures compatibility with tooling like Visual Studio's visual ResX editor
             
@@ -157,5 +154,93 @@ string customTypeConverter(Type type)
 
             Assert.Equal(expected, actual);
         }
+        
+        [Fact]
+        public void ResxDataNode_CreateForResXNullRef()
+        {
+            // Simulate an XML file stored in resources, which uses a ResXNullRef. The actual resx XML looks like:
+            /*
+               <assembly alias="System.Windows.Forms" name="System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" />
+               <data name="Test" type="System.Resources.ResXNullRef, System.Windows.Forms">
+                    <value />
+                </data>
+            */
+
+            var nodeInfo = new DataNodeInfo
+            {
+                Name = "Test",
+                ReaderPosition = new Point(1, 2),
+                TypeName = "System.Resources.ResXNullRef, System.Windows.Forms",
+                ValueData = "",
+            };
+            var dataNode = new ResXDataNode(nodeInfo, null);
+            var typeResolver = new AssemblyNamesTypeResolutionService(Array.Empty<AssemblyName>());
+            Assert.Equal("Test", dataNode.Name);
+            Assert.Null(dataNode.GetValue(typeResolver));
+
+            StringBuilder resxOutput = new StringBuilder();
+            using (ResXResourceWriter resx = new ResXResourceWriter(new StringWriter(resxOutput)))
+            {
+                resx.AddResource(dataNode);
+            }
+
+            Assert.Contains("<data name=\"Test\" type=\"System.Resources.ResXNullRef, System.Windows.Forms\">", resxOutput.ToString());
+        }
+        
+        [Fact]
+        public void ResxDataNode_ResXNullRef_RoundTrip()
+        {
+            object referencedFileContent = null;
+            var nodeInfo = new DataNodeInfo
+            {
+                Name = "ResxWithNullRef",
+                ReaderPosition = new Point(1, 2),
+                TypeName = "System.Resources.ResXNullRef, System.Windows.Forms",
+                ValueData = ""
+            };
+            var dataNode = new ResXDataNode(nodeInfo, null);
+
+            StringBuilder resxOutput = new StringBuilder();
+            using (ResXResourceWriter writer = new ResXResourceWriter(new StringWriter(resxOutput)))
+            {
+                writer.AddResource(dataNode);
+            }
+            using (ResXResourceReader reader = new ResXResourceReader(new StringReader(resxOutput.ToString())))
+            {
+                var dictionary = new Dictionary<object, object>();
+                IDictionaryEnumerator dictionaryEnumerator = reader.GetEnumerator();
+                while (dictionaryEnumerator.MoveNext())
+                {
+                    dictionary.Add(dictionaryEnumerator.Key, dictionaryEnumerator.Value);
+                }
+
+                Assert.Equal(referencedFileContent, dictionary.GetValueOrDefault(nodeInfo.Name));
+            }
+        }
+
+        [Fact]
+        public void ResxDataNode_ResXNullRefs_WrittenBackWithSameAssemblyInfo()
+        {
+            // This test ensures compatibility with tooling like Visual Studio's visual ResX editor
+
+            Encoding.RegisterProvider(CodePagesEncodingProvider.Instance);
+
+            string originalResx = Example.ResxWithNullRef;
+            StringBuilder writerOutput = new StringBuilder();
+
+            using (var reader = new ResXResourceReader(new StringReader(originalResx)))
+            {
+                reader.UseResXDataNodes = true;
+                var dataNodes = ReaderToNodes(reader);
+
+                using (ResXResourceWriter writer = new ResXResourceWriter(new StringWriter(writerOutput)))
+                {
+                    dataNodes.ForEach(writer.AddResource);
+                    writer.Generate();
+                }
+            }
+
+            Assert.Equal(originalResx, writerOutput.ToString());
+        }
     }
 }
diff --git a/Tests/ResxWithNullRef.resx b/Tests/ResxWithNullRef.resx
new file mode 100644
index 0000000..749ff9b
--- /dev/null
+++ b/Tests/ResxWithNullRef.resx
@@ -0,0 +1,65 @@
+<?xml version="1.0" encoding="utf-8"?>
+<root>
+  <xsd:schema id="root" xmlns="" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:msdata="urn:schemas-microsoft-com:xml-msdata">
+    <xsd:import namespace="http://www.w3.org/XML/1998/namespace" />
+    <xsd:element name="root" msdata:IsDataSet="true">
+      <xsd:complexType>
+        <xsd:choice maxOccurs="unbounded">
+          <xsd:element name="metadata">
+            <xsd:complexType>
+              <xsd:sequence>
+                <xsd:element name="value" type="xsd:string" minOccurs="0" />
+              </xsd:sequence>
+              <xsd:attribute name="name" use="required" type="xsd:string" />
+              <xsd:attribute name="type" type="xsd:string" />
+              <xsd:attribute name="mimetype" type="xsd:string" />
+              <xsd:attribute ref="xml:space" />
+            </xsd:complexType>
+          </xsd:element>
+          <xsd:element name="assembly">
+            <xsd:complexType>
+              <xsd:attribute name="alias" type="xsd:string" />
+              <xsd:attribute name="name" type="xsd:string" />
+            </xsd:complexType>
+          </xsd:element>
+          <xsd:element name="data">
+            <xsd:complexType>
+              <xsd:sequence>
+                <xsd:element name="value" type="xsd:string" minOccurs="0" msdata:Ordinal="1" />
+                <xsd:element name="comment" type="xsd:string" minOccurs="0" msdata:Ordinal="2" />
+              </xsd:sequence>
+              <xsd:attribute name="name" type="xsd:string" use="required" msdata:Ordinal="1" />
+              <xsd:attribute name="type" type="xsd:string" msdata:Ordinal="3" />
+              <xsd:attribute name="mimetype" type="xsd:string" msdata:Ordinal="4" />
+              <xsd:attribute ref="xml:space" />
+            </xsd:complexType>
+          </xsd:element>
+          <xsd:element name="resheader">
+            <xsd:complexType>
+              <xsd:sequence>
+                <xsd:element name="value" type="xsd:string" minOccurs="0" msdata:Ordinal="1" />
+              </xsd:sequence>
+              <xsd:attribute name="name" type="xsd:string" use="required" />
+            </xsd:complexType>
+          </xsd:element>
+        </xsd:choice>
+      </xsd:complexType>
+    </xsd:element>
+  </xsd:schema>
+  <resheader name="resmimetype">
+    <value>text/microsoft-resx</value>
+  </resheader>
+  <resheader name="version">
+    <value>2.0</value>
+  </resheader>
+  <resheader name="reader">
+    <value>System.Resources.ResXResourceReader, System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
+  </resheader>
+  <resheader name="writer">
+    <value>System.Resources.ResXResourceWriter, System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
+  </resheader>
+  <assembly alias="System.Windows.Forms" name="System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" />
+  <data name="ResxWithNullRef" type="System.Resources.ResXNullRef, System.Windows.Forms">
+    <value />
+  </data>
+</root>
\ No newline at end of file
diff --git a/Tests/System.Resources.Tests.csproj b/Tests/System.Resources.Tests.csproj
index 09d3baf..ae2ef37 100644
--- a/Tests/System.Resources.Tests.csproj
+++ b/Tests/System.Resources.Tests.csproj
@@ -26,9 +26,13 @@
     </Content>
   </ItemGroup>
   <ItemGroup>
+    <EmbeddedResource Remove="ResxWithNullRef.resx" />
     <EmbeddedResource Remove="TestResources\Files\ResxWithFileRef.resx" />
   </ItemGroup>
   <ItemGroup>
+    <Content Include="ResxWithNullRef.resx">
+      <SubType>Designer</SubType>
+    </Content>
     <Content Include="ResxWithFileRef.resx" />
   </ItemGroup>
   <ItemGroup>