Fix five correctness bugs in the binding engine + add regression tests

src/Core/ExistForAll.SimpleSettings/BindingContext.cs

@@ -28,14 +28,12 @@ public BindingContext(string section,
 		{
 			if (section == null) throw new ArgumentNullException(nameof(section));
 			if (key == null) throw new ArgumentNullException(nameof(key));
-			if (string.Equals(section, null, StringComparison.Ordinal)) throw new ArgumentNullException(nameof(section));
-			if (string.Equals(key, null, StringComparison.Ordinal)) throw new ArgumentNullException(nameof(key));
 
 			Section = section;
 			Key = key;
 			SettingsType = settingsType ?? throw new ArgumentNullException(nameof(settingsType));
 			PropertyInfo = propertyInfo ?? throw new ArgumentNullException(nameof(propertyInfo));
-			PropertyType = propertyInfo.DeclaringType!;
+			PropertyType = propertyInfo.PropertyType;
 			CurrentValue = currentValue;
 		}
 

src/Core/ExistForAll.SimpleSettings/Conversion/DefaultTypeConverter.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Globalization;
 
 namespace ExistForAll.SimpleSettings.Conversion
 {
@@ -11,7 +12,7 @@ public bool CanConvert(Type settingsType)
 
 		public object Convert(object value, Type settingsType)
 		{
-			return System.Convert.ChangeType(value, settingsType);
+			return System.Convert.ChangeType(value, settingsType, CultureInfo.InvariantCulture);
 		}
 	}
 }

src/Core/ExistForAll.SimpleSettings/Conversion/TypeConvertersCollections.cs

@@ -10,6 +10,7 @@ public TypeConvertersCollections(SettingsOptions settingsOptions)
 			AddLast(new UriTypeConvertor());
 			AddLast(new ArrayTypeConverter(settingsOptions, this));
 			AddLast(new EnumerableTypeConverter(settingsOptions, this));
+			AddLast(new EnumTypeConverter());
 			AddLast(new DefaultTypeConverter());
 		}
 	}

src/Core/ExistForAll.SimpleSettings/Core/SettingsOptionsValidator.cs

@@ -14,8 +14,9 @@ public void ValidateOptions(SettingsOptions settingsOptions)
 				throw new SettingsOptionsArgumentNullException();
 			}
 
-            if (!typeof(Attribute).GetTypeInfo().IsAssignableFrom(settingsOptions.AttributeType)) 
-                throw new SettingsOptionNonAttributeException(settingsOptions.AttributeType!);
+            if (settingsOptions.AttributeType != null &&
+                !typeof(Attribute).GetTypeInfo().IsAssignableFrom(settingsOptions.AttributeType)) 
+                throw new SettingsOptionNonAttributeException(settingsOptions.AttributeType);
 
 
             if (string.IsNullOrWhiteSpace(settingsOptions.ArraySplitDelimiter))

src/Core/ExistForAll.SimpleSettings/Resources.cs

@@ -43,10 +43,10 @@ public static string PropertyNotAllowNullMessage(string propertyName) =>
 			$@"[{propertyName}] is marked as Null not allowed, yet the value is null. please provide value via binder or attribute";
 
 		public static string TypeIsNotInterface(string typeName) =>
-			@"[{typeName}] is not an interface, SimpleSettings supports only interfaces";
+			$@"[{typeName}] is not an interface, SimpleSettings supports only interfaces";
 
         public static string SettingsOptionAttributeTypeMessage(Type type) =>
-            $"SimpleSettings support Attribute indication of interfaces, the type provided [${type.FullName}] is not an attribute.";
+            $"SimpleSettings support Attribute indication of interfaces, the type provided [{type.FullName}] is not an attribute.";
 
     }
 }

src/Tests/ExistForAll.SimpleSettings.UnitTests/Conversion/DefaultTypeConverterTests.cs

@@ -0,0 +1,75 @@
+using System.Globalization;
+using ExistForAll.SimpleSettings.Binder;
+
+namespace ExistForAll.SimpleSettings.UnitTests.Conversion
+{
+	public class DefaultTypeConverterTests
+	{
+		// The default SectionNameFormatter strips the leading "I": INumericSettings -> "NumericSettings".
+		private const string Section = "NumericSettings";
+
+		[Test]
+		[NotInParallel]
+		public async Task Build_DoubleFromString_UnderGermanCulture_ParsesInvariant()
+		{
+			var original = CultureInfo.CurrentCulture;
+			try
+			{
+				// In de-DE '.' is the group separator, so a culture-sensitive parse of "1.5" yields 15.
+				CultureInfo.CurrentCulture = new CultureInfo("de-DE");
+
+				var settings = BuildWith(nameof(INumericSettings.Value), "1.5")
+					.GetSettings<INumericSettings>();
+
+				await Assert.That(settings.Value).IsEqualTo(1.5d);
+			}
+			finally
+			{
+				CultureInfo.CurrentCulture = original;
+			}
+		}
+
+		[Test]
+		[NotInParallel]
+		public async Task Build_DecimalFromString_UnderGermanCulture_ParsesInvariant()
+		{
+			var original = CultureInfo.CurrentCulture;
+			try
+			{
+				CultureInfo.CurrentCulture = new CultureInfo("de-DE");
+
+				var settings = BuildWith(nameof(INumericSettings.Amount), "1234.56")
+					.GetSettings<INumericSettings>();
+
+				await Assert.That(settings.Amount).IsEqualTo(1234.56m);
+			}
+			finally
+			{
+				CultureInfo.CurrentCulture = original;
+			}
+		}
+
+		[Test]
+		public async Task Build_IntFromString_BindsValue()
+		{
+			var settings = BuildWith(nameof(INumericSettings.Count), "42")
+				.GetSettings<INumericSettings>();
+
+			await Assert.That(settings.Count).IsEqualTo(42);
+		}
+
+		private static SettingsBuilder BuildWith(string key, string value)
+		{
+			var collection = new InMemoryCollection();
+			collection.Add(Section, key, value);
+			return SettingsBuilder.CreateBuilder(x => x.AddSectionBinder(new InMemoryBinder(collection)));
+		}
+
+		public interface INumericSettings
+		{
+			double Value { get; set; }
+			decimal Amount { get; set; }
+			int Count { get; set; }
+		}
+	}
+}

src/Tests/ExistForAll.SimpleSettings.UnitTests/Conversion/EnumConversionTests.cs

@@ -0,0 +1,49 @@
+using System;
+using ExistForAll.SimpleSettings.Binder;
+
+namespace ExistForAll.SimpleSettings.UnitTests.Conversion
+{
+	public class EnumConversionTests
+	{
+		// The default SectionNameFormatter strips the leading "I": IEnumSettings -> "EnumSettings".
+		private const string Section = "EnumSettings";
+
+		[Test]
+		public async Task Build_EnumPropertyFromStringValue_BindsEnum()
+		{
+			var settings = BuildWith(nameof(IEnumSettings.Day), "Monday")
+				.GetSettings<IEnumSettings>();
+
+			await Assert.That(settings.Day).IsEqualTo(DayOfWeek.Monday);
+		}
+
+		[Test]
+		public async Task Build_EnumPropertyFromDefaultValue_BindsEnum()
+		{
+			// No binder: the value comes from the attribute default and is already the target type,
+			// so this path works even without the EnumTypeConverter registered — it guards the fix.
+			var settings = SettingsBuilder.CreateBuilder()
+				.GetSettings<IEnumWithDefault>();
+
+			await Assert.That(settings.Day).IsEqualTo(DayOfWeek.Friday);
+		}
+
+		private static SettingsBuilder BuildWith(string key, string value)
+		{
+			var collection = new InMemoryCollection();
+			collection.Add(Section, key, value);
+			return SettingsBuilder.CreateBuilder(x => x.AddSectionBinder(new InMemoryBinder(collection)));
+		}
+
+		public interface IEnumSettings
+		{
+			DayOfWeek Day { get; set; }
+		}
+
+		public interface IEnumWithDefault
+		{
+			[SettingsProperty(DefaultValue = DayOfWeek.Friday)]
+			DayOfWeek Day { get; set; }
+		}
+	}
+}