Fix indexing operators to validate negative indices

csharp/Platform.Data/LinkAddress.cs

@@ -42,14 +42,11 @@ public TLinkAddress this[int index]
             [MethodImpl(MethodImplOptions.AggressiveInlining)]
             get
             {
-                if (index == 0)
-                {
-                    return Index;
-                }
-                else
+                if (index != 0)
                 {
                     throw new IndexOutOfRangeException();
                 }
+                return Index;
             }
             [MethodImpl(MethodImplOptions.AggressiveInlining)]
             set => throw new NotSupportedException();

csharp/Platform.Data/Point.cs

@@ -57,14 +57,11 @@ public TLinkAddress this[int index]
             [MethodImpl(MethodImplOptions.AggressiveInlining)]
             get
             {
-                if (index < Size)
-                {
-                    return Index;
-                }
-                else
+                if (index < 0 || index >= Size)
                 {
                     throw new IndexOutOfRangeException();
                 }
+                return Index;
             }
             [MethodImpl(MethodImplOptions.AggressiveInlining)]
             set => throw new NotSupportedException();

examples/experiments/IndexerTest.cs

@@ -0,0 +1,101 @@
+using System;
+using Platform.Data;
+
+namespace Platform.Data.Tests
+{
+    public class IndexerTest
+    {
+        public static void Main()
+        {
+            Console.WriteLine("Testing Point<ulong> indexer...");
+            var point = new Point<ulong>(42UL, 3);
+
+            // Test valid indices
+            try
+            {
+                for (int i = 0; i < 3; i++)
+                {
+                    Console.WriteLine($"point[{i}] = {point[i]}");
+                }
+            }
+            catch (Exception ex)
+            {
+                Console.WriteLine($"Unexpected error with valid indices: {ex.Message}");
+            }
+
+            // Test negative index (should throw)
+            try
+            {
+                var result = point[-1];
+                Console.WriteLine($"ERROR: Negative index should have thrown exception, but got: {result}");
+            }
+            catch (IndexOutOfRangeException)
+            {
+                Console.WriteLine("✓ Negative index correctly throws IndexOutOfRangeException");
+            }
+            catch (Exception ex)
+            {
+                Console.WriteLine($"ERROR: Unexpected exception type: {ex.GetType().Name}: {ex.Message}");
+            }
+
+            // Test out-of-bounds index (should throw)
+            try
+            {
+                var result = point[3];
+                Console.WriteLine($"ERROR: Out-of-bounds index should have thrown exception, but got: {result}");
+            }
+            catch (IndexOutOfRangeException)
+            {
+                Console.WriteLine("✓ Out-of-bounds index correctly throws IndexOutOfRangeException");
+            }
+            catch (Exception ex)
+            {
+                Console.WriteLine($"ERROR: Unexpected exception type: {ex.GetType().Name}: {ex.Message}");
+            }
+
+            Console.WriteLine();
+            Console.WriteLine("Testing LinkAddress<ulong> indexer...");
+            var linkAddress = new LinkAddress<ulong>(123UL);
+
+            // Test valid index (0)
+            try
+            {
+                Console.WriteLine($"linkAddress[0] = {linkAddress[0]}");
+            }
+            catch (Exception ex)
+            {
+                Console.WriteLine($"Unexpected error with valid index 0: {ex.Message}");
+            }
+
+            // Test negative index (should throw)
+            try
+            {
+                var result = linkAddress[-1];
+                Console.WriteLine($"ERROR: Negative index should have thrown exception, but got: {result}");
+            }
+            catch (IndexOutOfRangeException)
+            {
+                Console.WriteLine("✓ Negative index correctly throws IndexOutOfRangeException");
+            }
+            catch (Exception ex)
+            {
+                Console.WriteLine($"ERROR: Unexpected exception type: {ex.GetType().Name}: {ex.Message}");
+            }
+
+            // Test positive index other than 0 (should throw)
+            try
+            {
+                var result = linkAddress[1];
+                Console.WriteLine($"ERROR: Index 1 should have thrown exception, but got: {result}");
+            }
+            catch (IndexOutOfRangeException)
+            {
+                Console.WriteLine("✓ Index 1 correctly throws IndexOutOfRangeException");
+            }
+            catch (Exception ex)
+            {
+                Console.WriteLine($"ERROR: Unexpected exception type: {ex.GetType().Name}: {ex.Message}");
+            }
+        }
+    }
+}

examples/experiments/IndexerTest.csproj

@@ -0,0 +1,11 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net8</TargetFramework>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="../../csharp/Platform.Data/Platform.Data.csproj" />
+  </ItemGroup>
+</Project>