diff --git a/src/Elastic.Clients.Elasticsearch.Serverless/Elastic.Clients.Elasticsearch.Serverless.csproj b/src/Elastic.Clients.Elasticsearch.Serverless/Elastic.Clients.Elasticsearch.Serverless.csproj
index 4e00bb4e38c..9cf4c7ee04e 100644
--- a/src/Elastic.Clients.Elasticsearch.Serverless/Elastic.Clients.Elasticsearch.Serverless.csproj
+++ b/src/Elastic.Clients.Elasticsearch.Serverless/Elastic.Clients.Elasticsearch.Serverless.csproj
@@ -23,6 +23,9 @@
   <ItemGroup>
     <PackageReference Include="Elastic.Transport" Version="0.4.26" />
   </ItemGroup>
+  <ItemGroup>
+    <PackageReference Condition="'$(TargetFramework)'=='net462' or '$(TargetFramework)'=='netstandard2.0'" Include="Microsoft.Bcl.HashCode" Version="1.1.1" />
+  </ItemGroup>
   <ItemGroup>
     <InternalsVisibleTo Include="Tests" Key="$(ExposedPublicKey)" />
     <InternalsVisibleTo Include="Tests.Domain" Key="$(ExposedPublicKey)" />
diff --git a/src/Elastic.Clients.Elasticsearch/Elastic.Clients.Elasticsearch.csproj b/src/Elastic.Clients.Elasticsearch/Elastic.Clients.Elasticsearch.csproj
index dcd3c9db9d8..794e77e3984 100644
--- a/src/Elastic.Clients.Elasticsearch/Elastic.Clients.Elasticsearch.csproj
+++ b/src/Elastic.Clients.Elasticsearch/Elastic.Clients.Elasticsearch.csproj
@@ -23,6 +23,9 @@
   <ItemGroup>
     <PackageReference Include="Elastic.Transport" Version="0.4.26" />
   </ItemGroup>
+  <ItemGroup>
+    <PackageReference Condition="'$(TargetFramework)'=='net462' or '$(TargetFramework)'=='netstandard2.0'" Include="Microsoft.Bcl.HashCode" Version="1.1.1" />
+  </ItemGroup>
   <ItemGroup>
     <InternalsVisibleTo Include="Tests" Key="$(ExposedPublicKey)" />
     <InternalsVisibleTo Include="Tests.Domain" Key="$(ExposedPublicKey)" />
diff --git a/src/Elastic.Clients.Elasticsearch/_Shared/Core/Fields/FieldValue.cs b/src/Elastic.Clients.Elasticsearch/_Shared/Core/Fields/FieldValue.cs
index a2b89956e86..3959cc2dc2b 100644
--- a/src/Elastic.Clients.Elasticsearch/_Shared/Core/Fields/FieldValue.cs
+++ b/src/Elastic.Clients.Elasticsearch/_Shared/Core/Fields/FieldValue.cs
@@ -28,7 +28,8 @@ namespace Elastic.Clients.Elasticsearch;
 /// therefore cannot be specifically typed.
 /// </summary>
 [JsonConverter(typeof(FieldValueConverter))]
-public readonly struct FieldValue : IEquatable<FieldValue>
+public readonly struct FieldValue :
+	IEquatable<FieldValue>
 {
 	internal FieldValue(ValueKind kind, object? value)
 	{
@@ -42,7 +43,7 @@ internal FieldValue(ValueKind kind, object? value)
 	public readonly ValueKind Kind { get; }
 
 	/// <summary>
-	/// The value contained within within this <see cref="FieldValue"/>.
+	/// The value contained within this <see cref="FieldValue"/>.
 	/// </summary>
 	public readonly object? Value { get; }
 
diff --git a/src/Elastic.Clients.Elasticsearch/_Shared/Core/Infer/Field/Field.cs b/src/Elastic.Clients.Elasticsearch/_Shared/Core/Infer/Field/Field.cs
index 2b0aef9bd91..b5f23d9cb42 100644
--- a/src/Elastic.Clients.Elasticsearch/_Shared/Core/Infer/Field/Field.cs
+++ b/src/Elastic.Clients.Elasticsearch/_Shared/Core/Infer/Field/Field.cs
@@ -4,7 +4,6 @@
 
 using System;
 using System.Diagnostics;
-using System.Diagnostics.CodeAnalysis;
 using System.Globalization;
 using System.Linq.Expressions;
 using System.Reflection;
@@ -15,7 +14,6 @@
 #if ELASTICSEARCH_SERVERLESS
 namespace Elastic.Clients.Elasticsearch.Serverless;
 #else
-
 namespace Elastic.Clients.Elasticsearch;
 #endif
 
@@ -25,6 +23,10 @@ public sealed class Field :
 	IEquatable<Field>,
 	IUrlParameter
 {
+#if !NET && !NETSTANDARD2_1_OR_GREATER
+	private static readonly char[] BoostSplit = ['^'];
+#endif
+
 	private readonly object _comparisonValue;
 	private readonly Type? _type;
 
@@ -67,22 +69,10 @@ public sealed class Field :
 
 	#region Constructors
 
-	public Field(string name) : this(name, null, null)
-	{
-	}
-
-	public Field(string name, double boost) : this(name, boost, null)
-	{
-	}
-
-	public Field(string name, string format) : this(name, null, format)
-	{
-	}
-
-	public Field(string name, double? boost, string? format)
+	public Field(string name, double? boost = null, string? format = null)
 	{
 		if (string.IsNullOrEmpty(name))
-			throw new ArgumentException($"{name} can not be null or empty.", nameof(name));
+			throw new ArgumentException("Field name can not be null or empty.", nameof(name));
 
 		Name = ParseFieldName(name, out var b);
 		Boost = b ?? boost;
@@ -91,6 +81,16 @@ public Field(string name, double? boost, string? format)
 		_comparisonValue = Name;
 	}
 
+	public Field(string name, double boost) :
+		this(name, boost, null)
+	{
+	}
+
+	public Field(string name, string format) :
+		this(name, null, format)
+	{
+	}
+
 	public Field(Expression expression, double? boost = null, string? format = null)
 	{
 		Expression = expression ?? throw new ArgumentNullException(nameof(expression));
@@ -117,21 +117,21 @@ public Field(PropertyInfo property, double? boost = null, string? format = null)
 
 	#region Factory Methods
 
-	public static Field? FromString(string? name) => string.IsNullOrEmpty(name) ? null : new Field(name);
+	public static Field FromString(string name) => new(name);
 
-	public static Field? FromExpression(Expression? expression) => expression is null ? null : new Field(expression);
+	public static Field FromExpression(Expression expression) => new(expression);
 
-	public static Field? FromProperty(PropertyInfo? property) => property is null ? null : new Field(property);
+	public static Field FromProperty(PropertyInfo property) => new(property);
 
 	#endregion Factory Methods
 
 	#region Conversion Operators
 
-	public static implicit operator Field?(string? name) => FromString(name);
+	public static implicit operator Field(string name) => FromString(name);
 
-	public static implicit operator Field?(Expression? expression) => FromExpression(expression);
+	public static implicit operator Field(Expression expression) => FromExpression(expression);
 
-	public static implicit operator Field?(PropertyInfo? property) => FromProperty(property);
+	public static implicit operator Field(PropertyInfo property) => FromProperty(property);
 
 	#endregion Conversion Operators
 
@@ -203,15 +203,7 @@ public override bool Equals(object? obj) =>
 			_ => false
 		};
 
-	public override int GetHashCode()
-	{
-		unchecked
-		{
-			var hashCode = _comparisonValue?.GetHashCode() ?? 0;
-			hashCode = (hashCode * 397) ^ (_type?.GetHashCode() ?? 0);
-			return hashCode;
-		}
-	}
+	public override int GetHashCode() => HashCode.Combine(_comparisonValue, _type);
 
 	#endregion Equality
 
@@ -243,20 +235,29 @@ public override string ToString() =>
 
 	#endregion Debugging
 
-	[return: NotNullIfNotNull(nameof(name))]
-	private static string? ParseFieldName(string? name, out double? boost)
+	private static string ParseFieldName(string name, out double? boost)
 	{
 		boost = null;
-		if (name is null)
-			return null;
 
-		var caretIndex = name.IndexOf('^');
-		if (caretIndex == -1)
+#if NET || NETSTANDARD2_1_OR_GREATER
+		if (!name.Contains('^', StringComparison.Ordinal))
 			return name;
+#else
+		if (name.IndexOf('^') == -1)
+			return name;
+#endif
 
-		var parts = name.Split(new[] { '^' }, 2, StringSplitOptions.RemoveEmptyEntries);
+#if NET || NETSTANDARD2_1_OR_GREATER
+		var parts = name.Split('^', 2, StringSplitOptions.RemoveEmptyEntries);
+#else
+		var parts = name.Split(BoostSplit, 2, StringSplitOptions.RemoveEmptyEntries);
+#endif
 		name = parts[0];
 		boost = double.Parse(parts[1], CultureInfo.InvariantCulture);
+
+		if (string.IsNullOrWhiteSpace(name))
+			throw new ArgumentException("Field name can not be null or empty.", nameof(name));
+
 		return name;
 	}
 }
diff --git a/src/Elastic.Clients.Elasticsearch/_Shared/Core/Infer/Fields/Fields.cs b/src/Elastic.Clients.Elasticsearch/_Shared/Core/Infer/Fields/Fields.cs
index cf610735c72..50ff90fde15 100644
--- a/src/Elastic.Clients.Elasticsearch/_Shared/Core/Infer/Fields/Fields.cs
+++ b/src/Elastic.Clients.Elasticsearch/_Shared/Core/Infer/Fields/Fields.cs
@@ -24,114 +24,168 @@ public sealed class Fields :
 	IEnumerable<Field>,
 	IUrlParameter
 {
-	internal readonly List<Field> ListOfFields;
+	private readonly List<Field> _listOfFields;
+
+	/// <summary>
+	/// The list of fields.
+	/// </summary>
+	public IReadOnlyList<Field> ListOfFields => _listOfFields;
 
 	#region Constructors
 
-	internal Fields() => ListOfFields = [];
+	public Fields() => _listOfFields = [];
 
-	internal Fields(IEnumerable<Field?> fields)
+	public Fields(IEnumerable<Field> fields)
 	{
 		if (fields is null)
 			throw new ArgumentNullException(nameof(fields));
 
-		ListOfFields = [.. fields.Where(f => f is not null)];
+		_listOfFields = [.. fields];
+
+		if (_listOfFields.Any(x => x is null))
+			throw new ArgumentException("Fields enumeration must not contain 'null' values.");
 	}
 
 	#endregion Constructors
 
 	#region Factory Methods
 
-	public static Fields? FromField(Field? field) => field is null
-		? null
-		: new Fields([field]);
+	public static Fields FromField(Field field)
+	{
+		if (field is null)
+			throw new ArgumentNullException(nameof(field));
+
+		return new Fields([field]);
+	}
+
+	public static Fields FromFields(Field[] fields)
+	{
+		if (fields is null)
+			throw new ArgumentNullException(nameof(fields));
+
+		return new Fields(fields);
+	}
+
+	public static Fields FromString(string name)
+	{
+		if (name is null)
+			throw new ArgumentNullException(nameof(name));
+
+		var split = name.Split(',');
+
+		return new Fields(split.Select(f => new Field(f)));
+	}
+
+	public static Fields FromStrings(string[] names)
+	{
+		if (names is null)
+			throw new ArgumentNullException(nameof(names));
+
+		return new Fields(names.Select(f => new Field(f)));
+	}
+
+	public static Fields FromExpression(Expression expression)
+	{
+		if (expression is null)
+			throw new ArgumentNullException(nameof(expression));
+
+		return new Fields([new Field(expression)]);
+	}
+
+	public static Fields FromExpressions(Expression[] expressions)
+	{
+		if (expressions is null)
+			throw new ArgumentNullException(nameof(expressions));
 
-	public static Fields? FromFields(Field[]? fields) => fields.IsNullOrEmpty()
-		? null
-		: new Fields(fields!);
+		return new Fields(expressions.Select(f => new Field(f)));
+	}
 
-	public static Fields? FromString(string? name) => name.IsNullOrEmptyCommaSeparatedList(out var split)
-		? null
-		: new Fields(split.Select(f => new Field(f)));
+	public static Fields FromExpression<T, TValue>(Expression<Func<T, TValue>> expression)
+	{
+		if (expression is null)
+			throw new ArgumentNullException(nameof(expression));
 
-	public static Fields? FromStrings(string[]? names) => names.IsNullOrEmpty()
-		? null
-		: new Fields(names!.Select(f => new Field(f)));
+		return new Fields([new Field(expression)]);
+	}
 
-	public static Fields? FromExpression(Expression? expression) => expression is null
-		? null
-		: new Fields([new Field(expression)]);
+	public static Fields FromExpressions<T>(Expression<Func<T, object?>>[] expressions)
+	{
+		if (expressions is null)
+			throw new ArgumentNullException(nameof(expressions));
 
-	public static Fields? FromExpressions(Expression[]? expressions) => expressions.IsNullOrEmpty()
-		? null
-		: new Fields(expressions!.Select(f => new Field(f)));
+		return new Fields(expressions.Select(f => new Field(f)));
+	}
 
-	public static Fields? FromExpression<T, TValue>(Expression<Func<T, TValue>>? expression) => expression is null
-		? null
-		: new Fields([new Field(expression)]);
+	public static Fields FromProperty(PropertyInfo property)
+	{
+		if (property is null)
+			throw new ArgumentNullException(nameof(property));
 
-	public static Fields? FromExpressions<T>(Expression<Func<T, object?>>[]? expressions) => expressions.IsNullOrEmpty()
-		? null
-		: new Fields(expressions!.Select(f => new Field(f)));
+		return new Fields([property]);
+	}
 
-	public static Fields? FromProperty(PropertyInfo? property) => property is null
-		? null
-		: new Fields([property]);
+	public static Fields FromProperties(PropertyInfo[] properties)
+	{
+		if (properties is null)
+			throw new ArgumentNullException(nameof(properties));
 
-	public static Fields? FromProperties(PropertyInfo[]? properties) => properties.IsNullOrEmpty()
-		? null
-		: new Fields(properties!.Select(f => new Field(f)));
+		return new Fields(properties.Select(f => new Field(f)));
+	}
 
 	#endregion Factory Methods
 
 	#region Conversion Operators
 
-	public static implicit operator Fields?(Field? field) => FromField(field);
+	public static implicit operator Fields(Field field) => FromField(field);
 
-	public static implicit operator Fields?(Field[]? fields) => FromFields(fields);
+	public static implicit operator Fields(Field[] fields) => FromFields(fields);
 
-	public static implicit operator Fields?(string? name) => FromString(name);
+	public static implicit operator Fields(string name) => FromString(name);
 
-	public static implicit operator Fields?(string[]? names) => FromStrings(names);
+	public static implicit operator Fields(string[] names) => FromStrings(names);
 
-	public static implicit operator Fields?(Expression? expression) => FromExpression(expression);
+	public static implicit operator Fields(Expression expression) => FromExpression(expression);
 
-	public static implicit operator Fields?(Expression[]? expressions) => FromExpressions(expressions);
+	public static implicit operator Fields(Expression[] expressions) => FromExpressions(expressions);
 
-	public static implicit operator Fields?(PropertyInfo? property) => FromProperty(property);
+	public static implicit operator Fields(PropertyInfo property) => FromProperty(property);
 
-	public static implicit operator Fields?(PropertyInfo[]? properties) => FromProperties(properties);
+	public static implicit operator Fields(PropertyInfo[] properties) => FromProperties(properties);
 
 	#endregion Conversion Operators
 
 	#region Combinator Methods
 
-	public Fields And(params Field?[] fields)
+	public Fields And(params Field[] fields)
 	{
 		if (fields is null)
 			throw new ArgumentNullException(nameof(fields));
 
-		ListOfFields.AddRange(fields.Where(f => f is not null));
+		// ReSharper disable once ConditionIsAlwaysTrueOrFalse
+		if (fields.Any(x => x is null))
+			throw new ArgumentException("Fields enumeration must not contain 'null' values.");
+
+		_listOfFields.AddRange(fields);
 
 		return this;
 	}
 
-	public Fields And(params string?[] names)
+	public Fields And(params string[] names)
 	{
 		if (names is null)
 			throw new ArgumentNullException(nameof(names));
 
-		ListOfFields.AddRange(names.Where(f => f is not null).Select(f => new Field(f)));
+		_listOfFields.AddRange(names.Select(f => new Field(f)));
 
 		return this;
 	}
 
-	public Fields And<T>(params Expression<Func<T, object>>?[] expressions)
+	public Fields And<T>(params Expression<Func<T, object>>[] expressions)
 	{
 		if (expressions is null)
 			throw new ArgumentNullException(nameof(expressions));
 
-		ListOfFields.AddRange(expressions.Where(f => f is not null).Select(f => new Field(f)));
+		_listOfFields.AddRange(expressions.Select(f => new Field(f)));
 
 		return this;
 	}
@@ -142,17 +196,17 @@ public Fields And<T, TValue>(Expression<Func<T, TValue>> expression, double? boo
 		if (expression is null)
 			throw new ArgumentNullException(nameof(expression));
 
-		ListOfFields.Add(new Field(expression, boost, format));
+		_listOfFields.Add(new Field(expression, boost, format));
 
 		return this;
 	}
 
-	public Fields And(params PropertyInfo?[] properties)
+	public Fields And(params PropertyInfo[] properties)
 	{
 		if (properties is null)
 			throw new ArgumentNullException(nameof(properties));
 
-		ListOfFields.AddRange(properties.Where(x => x is not null).Select(f => new Field(f)));
+		_listOfFields.AddRange(properties.Select(f => new Field(f)));
 
 		return this;
 	}
@@ -180,9 +234,9 @@ public override bool Equals(object? obj) =>
 			_ => false
 		};
 
-	public override int GetHashCode() => ListOfFields.GetHashCode();
+	public override int GetHashCode() => _listOfFields.GetHashCode();
 
-	public bool Equals(Fields? other) => (ListOfFields, other?.ListOfFields) switch
+	public bool Equals(Fields? other) => (_listOfFields, other?._listOfFields) switch
 	{
 		(null, null) => true,
 		({ } a, { } b) => (a.Count == b.Count) && !a.Except(b).Any(),
@@ -195,7 +249,7 @@ public override bool Equals(object? obj) =>
 
 	IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
 
-	public IEnumerator<Field> GetEnumerator() => ListOfFields.GetEnumerator();
+	public IEnumerator<Field> GetEnumerator() => _listOfFields.GetEnumerator();
 
 	#endregion IEnumerable
 
@@ -209,7 +263,7 @@ string IUrlParameter.GetString(ITransportConfiguration? settings)
 				$"Can not resolve {nameof(Fields)} if no {nameof(IElasticsearchClientSettings)} is provided");
 		}
 
-		return string.Join(",", ListOfFields.Select(f => ((IUrlParameter)f).GetString(elasticsearchClientSettings)));
+		return string.Join(",", _listOfFields.Select(f => ((IUrlParameter)f).GetString(elasticsearchClientSettings)));
 	}
 
 	#endregion IUrlParameter
@@ -217,8 +271,8 @@ string IUrlParameter.GetString(ITransportConfiguration? settings)
 	#region Debugging
 
 	public override string ToString() =>
-		$"Count: {ListOfFields.Count} [" +
-		string.Join(",", ListOfFields.Select((t, i) => $"({i + 1}: {t?.DebuggerDisplay})")) + "]";
+		$"Count: {_listOfFields.Count} [" +
+		string.Join(",", _listOfFields.Select((f, i) => $"({i + 1}: {f?.DebuggerDisplay})")) + "]";
 
 	private string DebuggerDisplay => ToString();
 
diff --git a/src/Elastic.Clients.Elasticsearch/_Shared/Core/Infer/Fields/FieldsConverter.cs b/src/Elastic.Clients.Elasticsearch/_Shared/Core/Infer/Fields/FieldsConverter.cs
index 2e7c514c3b3..9ad9863782e 100644
--- a/src/Elastic.Clients.Elasticsearch/_Shared/Core/Infer/Fields/FieldsConverter.cs
+++ b/src/Elastic.Clients.Elasticsearch/_Shared/Core/Infer/Fields/FieldsConverter.cs
@@ -31,7 +31,7 @@ internal sealed class FieldsConverter : JsonConverter<Fields>
 		}
 	}
 
-	public override void Write(Utf8JsonWriter writer, Fields value, JsonSerializerOptions options)
+	public override void Write(Utf8JsonWriter writer, Fields? value, JsonSerializerOptions options)
 	{
 		if (value is null)
 		{
@@ -65,7 +65,7 @@ internal sealed class SingleOrManyFieldsConverter : JsonConverter<Fields>
 		}
 	}
 
-	public override void Write(Utf8JsonWriter writer, Fields value, JsonSerializerOptions options)
+	public override void Write(Utf8JsonWriter writer, Fields? value, JsonSerializerOptions options)
 	{
 		if (value is null)
 		{