Fixed issue with FastDynamicObject.CopyTo.

src/CsvHelper/FastDynamicObject.cs

@@ -2,6 +2,7 @@
 using System.Collections;
 using System.Collections.Generic;
 using System.ComponentModel;
+using System.Diagnostics;
 using System.Dynamic;
 using System.Linq;
 using System.Linq.Expressions;
@@ -83,9 +84,21 @@ bool IDictionary<string, object>.ContainsKey(string key)
 
 	void ICollection<KeyValuePair<string, object>>.CopyTo(KeyValuePair<string, object>[] array, int arrayIndex)
 	{
-		foreach (var item in array)
+		if (arrayIndex < 0 || arrayIndex >= array.Length)
 		{
-			SetValue(item.Key, item.Value);
+			throw new ArgumentOutOfRangeException($"{nameof(arrayIndex)} must be greater than or equal to 0 and less then {nameof(array)} length.");
+		}
+
+		if (dict.Count + arrayIndex > array.Length)
+		{
+			throw new ArgumentException($"The number of elements in {nameof(FastDynamicMetaObject)} is greater than the available space from {nameof(arrayIndex)} to the end of the destination {nameof(array)}.");
+		}
+
+		var i = arrayIndex;
+		foreach (var pair in dict)
+		{
+			array[i] = pair;
+			i++;
 		}
 	}
 

tests/CsvHelper.Tests/CsvHelper.Tests.csproj

@@ -1,8 +1,8 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
 	<PropertyGroup>
-		<TargetFrameworks>net8.0;net7.0;net6.0;net48;net47;net462</TargetFrameworks>
-		<!--<TargetFrameworks>net8.0</TargetFrameworks>-->
+		<!--<TargetFrameworks>net8.0;net7.0;net6.0;net48;net47;net462</TargetFrameworks>-->
+		<TargetFrameworks>net8.0</TargetFrameworks>
 		<LangVersion>preview</LangVersion>
 		<SignAssembly>True</SignAssembly>
 		<AssemblyOriginatorKeyFile>CsvHelper.snk</AssemblyOriginatorKeyFile>

tests/CsvHelper.Tests/Dynamic/FastDynamicTests.cs

@@ -0,0 +1,99 @@
+using System;
+using System.Collections.Generic;
+using Xunit;
+
+namespace CsvHelper.Tests.Dynamic
+{
+	public class FastDynamicObjectTests
+	{
+		[Fact]
+		public void Dynamic_SetAndGet_Works()
+		{
+			dynamic obj = new FastDynamicObject();
+			obj.Id = 1;
+			obj.Name = "one";
+
+			var id = obj.Id;
+			var name = obj.Name;
+
+			Assert.Equal(1, id);
+			Assert.Equal("one", name);
+		}
+
+		[Fact]
+		public void CopyTo_NegativeIndex_Throws()
+		{
+			IDictionary<string, object> d = new FastDynamicObject();
+			var a = new KeyValuePair<string, object>[1];
+
+			Assert.Throws<ArgumentOutOfRangeException>(() => d.CopyTo(a, -1));
+		}
+
+		[Fact]
+		public void CopyTo_IndexLargerThanArrayLength_Throws()
+		{
+			IDictionary<string, object> d = new FastDynamicObject();
+			var a = new KeyValuePair<string, object>[1];
+
+			Assert.Throws<ArgumentOutOfRangeException>(() => d.CopyTo(a, a.Length));
+		}
+
+		[Fact]
+		public void CopyTo_SourceIsLargerThanDestination_Throws()
+		{
+			IDictionary<string, object> d = new FastDynamicObject();
+			d["a"] = 1;
+			d["b"] = 2;
+			var a = new KeyValuePair<string, object>[1];
+
+			Assert.Throws<ArgumentException>(() => d.CopyTo(a, 0));
+		}
+
+		[Fact]
+		public void CopyTo_IndexGreaterThanZeroAndSourceIsLargerThanDestination_Throws()
+		{
+			IDictionary<string, object> d = new FastDynamicObject();
+			d["a"] = 1;
+			d["b"] = 2;
+			var a = new KeyValuePair<string, object>[2];
+
+			Assert.Throws<ArgumentException>(() => d.CopyTo(a, 1));
+		}
+
+		[Fact]
+		public void CopyTo_StartAtZero_Copies()
+		{
+			IDictionary<string, object> d = new FastDynamicObject();
+			d["a"] = 1;
+			d["b"] = 2;
+			var a = new KeyValuePair<string, object>[2];
+
+			d.CopyTo(a, 0);
+
+			Assert.Equal("a", a[0].Key);
+			Assert.Equal(1, a[0].Value);
+			Assert.Equal("b", a[1].Key);
+			Assert.Equal(2, a[1].Value);
+		}
+
+		[Fact]
+		public void CopyTo_StartGreaterThanZero_Copies()
+		{
+			IDictionary<string, object> d = new FastDynamicObject();
+			d["a"] = 1;
+			d["b"] = 2;
+			var a = new KeyValuePair<string, object>[4];
+
+			d.CopyTo(a, 1);
+
+			Assert.Null(a[0].Key);
+			Assert.Null(a[0].Value);
+			Assert.Equal("a", a[1].Key);
+			Assert.Equal(1, a[1].Value);
+			Assert.Equal("b", a[2].Key);
+			Assert.Equal(2, a[2].Value);
+			Assert.Null(a[3].Key);
+			Assert.Null(a[3].Value);
+		}
+	}
+}