Support Null configuration

src/libraries/Microsoft.Extensions.Configuration.Binder/gen/Emitter/ExceptionMessages.cs

@@ -13,7 +13,7 @@ internal static class ExceptionMessages
                 public const string CannotBindToConstructorParameter = "Cannot create instance of type '{0}' because one or more parameters cannot be bound to. Constructor parameters cannot be declared as in, out, or ref. Invalid parameters are: '{1}'";
                 public const string CannotSpecifyBindNonPublicProperties = "The configuration binding source generator does not support 'BinderOptions.BindNonPublicProperties'.";
                 public const string ConstructorParametersDoNotMatchProperties = "Cannot create instance of type '{0}' because one or more parameters cannot be bound to. Constructor parameters must have corresponding properties. Fields are not supported. Missing properties are: '{1}'";
-                public const string FailedBinding = "Failed to convert configuration value at '{0}' to type '{1}'.";
+                public const string FailedBinding = "Failed to convert configuration value '{0}' at '{1}' to type '{2}'.";
                 public const string MissingConfig = "'{0}' was set on the provided {1}, but the following properties were not found on the instance of {2}: {3}";
                 public const string MissingPublicInstanceConstructor = "Cannot create instance of type '{0}' because it is missing a public instance constructor.";
                 public const string MultipleParameterizedConstructors = "Cannot create instance of type '{0}' because it has multiple public parameterized constructors.";

src/libraries/Microsoft.Extensions.Configuration.Binder/gen/Emitter/Helpers.cs

@@ -114,6 +114,7 @@ private static class Identifier
                 public const string HasValue = nameof(HasValue);
                 public const string IConfiguration = nameof(IConfiguration);
                 public const string IConfigurationSection = nameof(IConfigurationSection);
+                public const string ConfigurationSection = nameof(ConfigurationSection);
                 public const string Int32 = "int";
                 public const string InterceptsLocation = nameof(InterceptsLocation);
                 public const string InvalidOperationException = nameof(InvalidOperationException);
@@ -133,6 +134,7 @@ private static class Identifier
                 public const string Type = nameof(Type);
                 public const string Uri = nameof(Uri);
                 public const string ValidateConfigurationKeys = nameof(ValidateConfigurationKeys);
+                public const string TryGetConfigurationValue = nameof(TryGetConfigurationValue);
                 public const string Value = nameof(Value);
             }
 

src/libraries/Microsoft.Extensions.Configuration.Binder/src/ConfigurationBinder.cs

@@ -311,7 +311,8 @@ private static void BindProperty(PropertyInfo property, object instance, IConfig
             // For property binding, there are some cases when HasNewValue is not set in BindingPoint while a non-null Value inside that object can be retrieved from the property getter.
             // As example, when binding a property which not having a configuration entry matching this property and the getter can initialize the Value.
             // It is important to call the property setter as the setters can have a logic adjusting the Value.
-            if (!propertyBindingPoint.IsReadOnly && propertyBindingPoint.Value is not null)
+            // Otherwise, if the HasNewValue set to true, it means that the property setter should be called anyway as encountering a new value.
+            if (!propertyBindingPoint.IsReadOnly && (propertyBindingPoint.Value is not null || propertyBindingPoint.HasNewValue))
             {
                 property.SetValue(instance, propertyBindingPoint.Value);
             }
@@ -338,15 +339,41 @@ private static void BindInstance(
                 return;
             }
 
-            var section = config as IConfigurationSection;
-            string? configValue = section?.Value;
-            if (configValue != null && TryConvertValue(type, configValue, section?.Path, out object? convertedValue, out Exception? error))
+            IConfigurationSection? section;
+            string? configValue;
+            bool isConfigurationExist;
+
+            if (config is ConfigurationSection configSection)
+            {
+                section = configSection;
+                isConfigurationExist = configSection.TryGetValue(key:null, out configValue);
+            }
+            else
+            {
+                section = config as IConfigurationSection;
+                configValue = section?.Value;
+                isConfigurationExist = configValue != null;
+            }
+
+            if (isConfigurationExist && TryConvertValue(type, configValue, section?.Path, out object? convertedValue, out Exception? error))
             {
                 if (error != null)
                 {
                     throw error;
                 }
 
+                if (type == typeof(byte[]) && bindingPoint.Value is byte[] byteArray && byteArray.Length > 0)
+                {
+                    if (convertedValue is byte[] convertedByteArray && convertedByteArray.Length > 0)
+                    {
+                        Array a = Array.CreateInstance(type.GetElementType()!, byteArray.Length + convertedByteArray.Length);
+                        Array.Copy(byteArray, a, byteArray.Length);
+                        Array.Copy(convertedByteArray, 0, a, byteArray.Length, convertedByteArray.Length);
+                        bindingPoint.TrySetValue(a);
+                    }
+                    return;
+                }
+
                 // Leaf nodes are always reinitialized
                 bindingPoint.TrySetValue(convertedValue);
                 return;
@@ -476,13 +503,29 @@ private static void BindInstance(
                     if (options.ErrorOnUnknownConfiguration)
                     {
                         Debug.Assert(section is not null);
-                        throw new InvalidOperationException(SR.Format(SR.Error_FailedBinding, section.Path, type));
+                        throw new InvalidOperationException(SR.Format(SR.Error_FailedBinding, configValue, section.Path, type));
                     }
                 }
-                else if (isParentCollection && bindingPoint.Value is null)
+                else
                 {
-                    // Try to create the default instance of the type
-                    bindingPoint.TrySetValue(CreateInstance(type, config, options, out _));
+                    if (isParentCollection && bindingPoint.Value is null)
+                    {
+                        // Try to create the default instance of the type
+                        bindingPoint.TrySetValue(CreateInstance(type, config, options, out _));
+                    }
+                    else if (isConfigurationExist && bindingPoint.Value is null)
+                    {
+                        // Don't override the existing array in bindingPoint.Value if it is already set.
+                        if (type.IsArray || IsImmutableArrayCompatibleInterface(type))
+                        {
+                            // When having configuration value set to empty string, we create an empty array
+                            bindingPoint.TrySetValue(configValue is null ? null : Array.CreateInstance(type.GetElementType()!, 0));
+                        }
+                        else
+                        {
+                            bindingPoint.TrySetValue(bindingPoint.Value); // force setting null value
+                        }
+                    }
                 }
             }
         }
@@ -930,7 +973,7 @@ private static Array BindArray(Type type, IEnumerable? source, IConfiguration co
         private static bool TryConvertValue(
             [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.All)]
             Type type,
-            string value, string? path, out object? result, out Exception? error)
+            string? value, string? path, out object? result, out Exception? error)
         {
             error = null;
             result = null;
@@ -954,11 +997,14 @@ private static bool TryConvertValue(
             {
                 try
                 {
-                    result = converter.ConvertFromInvariantString(value);
+                    if (value is not null)
+                    {
+                        result = converter.ConvertFromInvariantString(value);
+                    }
                 }
                 catch (Exception ex)
                 {
-                    error = new InvalidOperationException(SR.Format(SR.Error_FailedBinding, path, type), ex);
+                    error = new InvalidOperationException(SR.Format(SR.Error_FailedBinding, value, path, type), ex);
                 }
                 return true;
             }
@@ -967,11 +1013,14 @@ private static bool TryConvertValue(
             {
                 try
                 {
-                    result = Convert.FromBase64String(value);
+                    if (value is not null )
+                    {
+                        result = value == string.Empty ? Array.Empty<byte>() : Convert.FromBase64String(value);
+                    }
                 }
                 catch (FormatException ex)
                 {
-                    error = new InvalidOperationException(SR.Format(SR.Error_FailedBinding, path, type), ex);
+                    error = new InvalidOperationException(SR.Format(SR.Error_FailedBinding, value, path, type), ex);
                 }
                 return true;
             }

src/libraries/Microsoft.Extensions.Configuration.Binder/src/Microsoft.Extensions.Configuration.Binder.csproj

@@ -33,6 +33,7 @@
 
   <ItemGroup>
     <ProjectReference Include="$(LibrariesProjectRoot)Microsoft.Extensions.Configuration.Abstractions\src\Microsoft.Extensions.Configuration.Abstractions.csproj" />
+    <ProjectReference Include="$(LibrariesProjectRoot)Microsoft.Extensions.Configuration\src\Microsoft.Extensions.Configuration.csproj" />
     <ProjectReference Include="..\gen\Microsoft.Extensions.Configuration.Binder.SourceGeneration.csproj"
                       ReferenceOutputAssembly="false"
                       PackAsAnalyzer="true" />

src/libraries/Microsoft.Extensions.Configuration.Binder/src/Resources/Strings.resx

@@ -1,17 +1,17 @@
 <?xml version="1.0" encoding="utf-8"?>
 <root>
-  <!-- 
-    Microsoft ResX Schema 
-    
+  <!--
+    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 
+
+    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>
@@ -26,36 +26,36 @@
         <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 
+
+    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 
+
+    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 
+
+    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 
+
+    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 
+    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 
+    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 
+    value   : The object must be serialized into a byte array
             : using a System.ComponentModel.TypeConverter
             : and then encoded with base64 encoding.
     -->
@@ -127,7 +127,7 @@
     <value>Cannot create instance of type '{0}' because one or more parameters cannot be bound to. Constructor parameters must have corresponding properties. Fields are not supported. Missing properties are: '{1}'</value>
   </data>
   <data name="Error_FailedBinding" xml:space="preserve">
-    <value>Failed to convert configuration value at '{0}' to type '{1}'.</value>
+    <value>Failed to convert configuration value '{0}' at '{1}' to type '{2}'.</value>
   </data>
   <data name="Error_FailedToActivate" xml:space="preserve">
     <value>Failed to create instance of type '{0}'.</value>
@@ -153,4 +153,4 @@
   <data name="Error_UnsupportedMultidimensionalArray" xml:space="preserve">
     <value>Cannot create instance of type '{0}' because multidimensional arrays are not supported.</value>
   </data>
-</root>
+</root>

src/libraries/Microsoft.Extensions.Configuration.Binder/tests/Common/ConfigurationBinderTests.Collections.cs

@@ -61,7 +61,7 @@ public void GetListNullValues()
             var list = new List<string>();
             config.GetSection("StringList").Bind(list);
 
-            Assert.Empty(list);
+            Assert.Equal([ null, null, null, null ], list);
         }
 
         [ConditionalFact(typeof(TestHelpers), nameof(TestHelpers.NotSourceGenMode))] // Ensure exception messages are in sync
@@ -2182,9 +2182,10 @@ public void CanBindInstantiatedIEnumerableWithNullItems()
 
             var options = config.Get<ComplexOptions>()!;
 
-            Assert.Equal(2, options.InstantiatedIEnumerable.Count());
-            Assert.Equal("Yo1", options.InstantiatedIEnumerable.ElementAt(0));
-            Assert.Equal("Yo2", options.InstantiatedIEnumerable.ElementAt(1));
+            Assert.Equal(3, options.InstantiatedIEnumerable.Count());
+            Assert.Null(options.InstantiatedIEnumerable.ElementAt(0));
+            Assert.Equal("Yo1", options.InstantiatedIEnumerable.ElementAt(1));
+            Assert.Equal("Yo2", options.InstantiatedIEnumerable.ElementAt(2));
         }
 
         [Fact]

src/libraries/Microsoft.Extensions.Configuration.Binder/tests/Common/ConfigurationBinderTests.TestClasses.cs

@@ -1147,5 +1147,36 @@ public enum MyValue
             Value2,
             Value3
         }
+
+        public class NullConfiguration
+        {
+            public NullConfiguration()
+            {
+                // Initialize with non-default value to ensure binding will override these values
+                StringProperty1 = "Initial Value 1";
+                StringProperty2 = "Initial Value 2";
+                StringProperty3 = "Initial Value 3";
+
+                IntProperty1 = 123;
+                IntProperty2 = 456;
+            }
+            public string? StringProperty1 { get; set; }
+            public string? StringProperty2 { get; set; }
+            public string? StringProperty3 { get; set; }
+
+            public int? IntProperty1 { get; set; }
+            public int? IntProperty2 { get; set; }
+        }
+
+        public class ArraysContainer
+        {
+            public string[] StringArray1 { get; set; }
+            public string[] StringArray2 { get; set; }
+            public string[] StringArray3 { get; set; }
+
+            public byte[] ByteArray1 { get; set; }
+            public byte[] ByteArray2 { get; set; }
+            public byte[] ByteArray3 { get; set; }
+        }
     }
 }