fix polyfills visibility (#910)

Co-authored-by: Roland Pheasant <roland_pheasant@hotmail.com>

src/DynamicData/DynamicData.csproj

@@ -29,8 +29,4 @@ Dynamic Data is a comprehensive caching and data manipulation solution which int
     </Compile>
   </ItemGroup>
 
-  <ItemGroup>
-    <Compile Remove="Polyfills/ListEnsureCapacity.cs" Condition="'$(TargetFramework)' == 'net6.0' Or '$(TargetFramework)' == 'net7.0' Or '$(TargetFramework)' == 'net8.0'" />
-  </ItemGroup>
-
-</Project>
+</Project>

src/DynamicData/Polyfills/CompilerFeatureRequiredAttribute.cs

@@ -1,7 +1,7 @@
 // Copyright (c) 2011-2023 Roland Pheasant. All rights reserved.
 // Roland Pheasant licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for full license information.
-
+#if !NET7_0_OR_GREATER
 namespace System.Runtime.CompilerServices;
 
 // Allows use of the C#11 `required` keyword, internally within this library, when targeting frameworks older than .NET 7.
@@ -19,3 +19,4 @@ public const string RequiredMembers
 
     public bool IsOptional { get; init; }
 }
+#endif

src/DynamicData/Polyfills/IsExternalInit.cs

@@ -1,10 +1,9 @@
 // Copyright (c) 2011-2023 Roland Pheasant. All rights reserved.
 // Roland Pheasant licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for full license information.
-
+#if !NETCOREAPP
 namespace System.Runtime.CompilerServices;
 
 // Allows use of the C#11 `init` keyword, internally within this library, when targeting frameworks older than .NET 5.
-internal sealed class IsExternalInit
-{
-}
+internal sealed class IsExternalInit;
+#endif

src/DynamicData/Polyfills/ListEnsureCapacity.cs

@@ -1,16 +1,15 @@
 // Copyright (c) 2011-2023 Roland Pheasant. All rights reserved.
 // Roland Pheasant licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for full license information.
-
+#if !NETCOREAPP
 namespace System.Collections.Generic;
 
 internal static class ListEnsureCapacity
 {
-    public static void EnsureCapacity<T>(
-        this List<T> list,
-        int capacity)
+    public static void EnsureCapacity<T>(this List<T> list, int capacity)
     {
         if (list.Capacity < capacity)
             list.Capacity = capacity;
     }
 }
+#endif

src/DynamicData/Polyfills/RequiredMemberAttribute.cs

@@ -1,15 +1,13 @@
 // Copyright (c) 2011-2023 Roland Pheasant. All rights reserved.
 // Roland Pheasant licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for full license information.
-
+#if !NET7_0_OR_GREATER
 using System.ComponentModel;
 
 namespace System.Runtime.CompilerServices;
 
 // Allows use of the C#11 `required` keyword, internally within this library, when targeting frameworks older than .NET 7.
-[AttributeUsage(AttributeTargets.Class | AttributeTargets.Struct | AttributeTargets.Field | AttributeTargets.Property, AllowMultiple = false, Inherited = false)]
+[AttributeUsage(AttributeTargets.Class | AttributeTargets.Struct | AttributeTargets.Field | AttributeTargets.Property, Inherited = false)]
 [EditorBrowsable(EditorBrowsableState.Never)]
-internal sealed class RequiredMemberAttribute
-    : Attribute
-{
-}
+internal sealed class RequiredMemberAttribute : Attribute;
+#endif