remove netstandard1.6 replace with netstandard2.0

source/Directory.Build.props

@@ -1,6 +1,6 @@
 <Project>
   <PropertyGroup>
-    <TargetFrameworks>net40;net451;netstandard1.6;net8.0</TargetFrameworks>
+    <TargetFrameworks>net40;net451;netstandard2.0;net8.0</TargetFrameworks>
     <PlatformAlias>netstandard</PlatformAlias>
     <OutputPath>$(MSBuildThisFileDirectory)\..\output\$(Configuration)</OutputPath>
     <PackageOutputPath>$(MSBuildThisFileDirectory)\..\output</PackageOutputPath>

source/icu.net.tests/SetUpFixture.cs

@@ -16,7 +16,7 @@ private static bool IsWindows
 			{
 				// See Icu.Platform. Unfortunately that's internal, so we can't use it.
 
-#if !NETSTANDARD1_6 && !NET
+#if NETFRAMEWORK
 				// See http://www.mono-project.com/docs/faq/technical/#how-to-detect-the-execution-platform
 				switch ((int)Environment.OSVersion.Platform)
 				{

source/icu.net/Collation/Collator.cs

@@ -14,10 +14,7 @@ namespace Icu.Collation
 	/// You use this class to build searching and sorting routines for natural
 	/// language text.
 	/// </summary>
-	public abstract class Collator : IComparer<string>, IDisposable
-#if FEATURE_ICLONEABLE
-		, ICloneable
-#endif
+	public abstract class Collator : IComparer<string>, IDisposable, ICloneable
 	{
 		/// <summary>
 		/// Gets or sets the minimum strength that will be used in comparison
@@ -194,18 +191,13 @@ static public SortKey CreateSortKey(string originalString, byte[] keyData, int k
 
 			var options = CompareOptions.None;
 
-#if NETSTANDARD1_6
-			var sortKey = new SortKey(CultureInfo.InvariantCulture.Name, originalString, options, keyData);
-#else
 			var sortKey = CultureInfo.InvariantCulture.CompareInfo.GetSortKey(string.Empty, options);
 			SetInternalOriginalStringField(sortKey, originalString);
 			SetInternalKeyDataField(sortKey, keyData, keyDataLength);
-#endif
 
 			return sortKey;
 		}
 
-#if !NETSTANDARD1_6
 		private static void SetInternalKeyDataField(SortKey sortKey, byte[] keyData, int keyDataLength)
 		{
 			var keyDataCopy = new byte[keyDataLength];
@@ -275,7 +267,6 @@ private static bool IsRunningOnMono()
 		{
 			return Type.GetType("Mono.Runtime") != null;
 		}
-#endif
 
 		/// <summary>
 		/// Simple class to allow passing collation error info back to the caller of CheckRules.

source/icu.net/Collation/RuleBasedCollator.cs

@@ -3,12 +3,9 @@
 using System;
 using System.Collections.Generic;
 using System.Runtime.InteropServices;
-#if NETSTANDARD1_6
-using Icu;
-#else
 using System.Globalization;
 using System.Runtime.ConstrainedExecution;
-#endif
+
 
 namespace Icu.Collation
 {
@@ -30,9 +27,7 @@
 			/// true if the handle is released successfully; otherwise, in the event of a catastrophic failure, false.
 			/// In this case, it generates a ReleaseHandleFailed Managed Debugging Assistant.
 			///</returns>
-#if !NETSTANDARD1_6 && !NET
 			[ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)]
-#endif
 			protected override bool ReleaseHandle()
 			{
 				try

source/icu.net/Locale.cs

@@ -11,10 +11,7 @@ namespace Icu
 	/// <summary>
 	/// A Locale object represents a specific geographical, political, or cultural region.
 	/// </summary>
-	public class Locale
-#if FEATURE_ICLONEABLE
-		: ICloneable
-#endif
+	public class Locale	: ICloneable
 	{
 		/// <summary>
 		/// Construct a default locale object, a Locale for the default locale ID

source/icu.net/Platform.cs

@@ -29,19 +29,7 @@ internal static class Platform
 		public const string x64 = nameof(x64);
 		public const string x86 = nameof(x86);
 
-		public static string ProcessArchitecture
-		{
-			get {
-
-#if NET || NETSTANDARD
-				// Workaround described here since the API does not exist:
-				// https://github.com/dotnet/corefx/issues/999#issuecomment-75907756
-				return IntPtr.Size == 4 ? x86 : x64;
-#else
-				return Environment.Is64BitProcess ? x64 : x86;
-#endif
-			}
-		}
+		public static string ProcessArchitecture => Environment.Is64BitProcess ? x64 : x86;
 
 		public static OperatingSystemType OperatingSystem
 		{

source/icu.net/SafeEnumeratorHandle.cs

@@ -2,10 +2,8 @@
 // This software is licensed under the MIT license (http://opensource.org/licenses/MIT)
 using System;
 using System.Runtime.InteropServices;
-
-#if !NETSTANDARD1_6
 using System.Runtime.ConstrainedExecution;
-#endif
+
 
 namespace Icu
 {
@@ -23,9 +21,7 @@
 		/// failure, false. In this case, it generates a ReleaseHandleFailed Managed Debugging
 		/// Assistant.
 		///</returns>
-#if !NETSTANDARD1_6 && !NET
 		[ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)]
-#endif
 		protected override bool ReleaseHandle()
 		{
 			NativeMethods.uenum_close(handle);

source/icu.net/icu.net.csproj

@@ -5,35 +5,17 @@
     <Description>icu.net is a C# Wrapper around ICU4C</Description>
     <PackageReadmeFile>README.md</PackageReadmeFile>
   </PropertyGroup>
-  <!-- Full .NET Framework properties -->
-  <PropertyGroup Condition="'$(TargetFramework)' != 'netstandard1.6'">
-    <DefineConstants>$(DefineConstants);FEATURE_ICLONEABLE</DefineConstants>
-  </PropertyGroup>
   <ItemGroup>
     <PackageReference Include="GitVersion.MsBuild" Version="5.10.3" PrivateAssets="all" />
     <PackageReference Include="JetBrains.Annotations" Version="2022.1.0" PrivateAssets="all" />
     <PackageReference Include="Microsoft.SourceLink.GitHub" Version="1.1.1" PrivateAssets="all" />
     <PackageReference Include="SIL.ReleaseTasks" Version="2.5.0" PrivateAssets="all" />
-  </ItemGroup>
-  <ItemGroup Condition="'$(TargetFramework)' == 'netstandard1.6'">
-    <!--System.ValueTuple v4.5 caused MSB3277 when consuming LibChorus in LibTriboroughBridge-ChorusPlugin -->
-    <!-- The reason is that .NET Standard comes with System.ValueTuple AssemblyVersion 4.0.2 -->
-    <!-- which corresponds to package version 4.4.0 -->
-    <PackageReference Include="System.ValueTuple" Version="4.4.0" />
-    <PackageReference Include="System.Diagnostics.TraceSource" Version="4.3.0" />
-    <PackageReference Include="System.Runtime.InteropServices.RuntimeInformation" Version="4.3.0" />
-  </ItemGroup>
-  <ItemGroup Condition="'$(TargetFramework)' != 'netstandard1.6'">
     <PackageReference Include="System.ValueTuple" Version="4.5.0" />
   </ItemGroup>
   <ItemGroup Condition="'$(TargetFramework)' != 'net40'">
     <PackageReference Include="Microsoft.Extensions.DependencyModel" Version="2.0.4" />
   </ItemGroup>
 
-  <ItemGroup Condition="'$(TargetFramework)' != 'netstandard1.6'">
-    <Compile Remove="SortKey.cs" />
-  </ItemGroup>
-
   <!-- ICU must be installed using MacPorts before this will work -->
   <ItemGroup>
     <Content Include="/opt/local/lib/*.dylib" Condition="$([MSBuild]::IsOSPlatform('OSX'))">