[Foundation] Add Support for DotNet Attributes (#12603)

Co-authored-by: tj_devel709 <antlambe@microsoft.com>

src/Foundation/NSAttributedString.iOS.cs

@@ -30,6 +30,7 @@
 using ObjCRuntime;
 using Foundation;
 using CoreGraphics;
+using System.Runtime.Versioning;
 
 #if !MONOMAC
 using UIKit;
@@ -281,7 +282,12 @@ public NSDictionary WeakDefaultAttributes {
 #if !COREBUILD && !TVOS && !WATCH
 		// documentation is unclear if an NSString or an NSUrl should be used...
 		// but providing an `NSString` throws a `NSInvalidArgumentException Reason: (null) is not a file URL`
+#if !NET
 		[Mac (10, 15), iOS (13, 0)]
+#else
+		[SupportedOSPlatform ("ios13.0")]
+		[SupportedOSPlatform ("macos10.15")]
+#endif
 		public NSUrl ReadAccessUrl {
 			get {
 				Dictionary.TryGetValue (NSAttributedStringDocumentReadingOptionKeys.ReadAccessUrlKey, out var value);

src/Foundation/NSCalendar.cs

@@ -31,6 +31,7 @@
 using CoreFoundation;
 using Foundation;
 using CoreGraphics;
+using System.Runtime.Versioning;
 #if !WATCH
 using CoreMedia;
 #endif
@@ -39,11 +40,15 @@ namespace Foundation {
 	public enum NSCalendarType {
 		Gregorian, Buddhist, Chinese, Hebrew, Islamic, IslamicCivil, Japanese, [Obsolete] RepublicOfChina, Persian, Indian, ISO8601,
 		Coptic, EthiopicAmeteAlem, EthiopicAmeteMihret,
+#if !NET
 		[Mac (10, 10)]
 		[iOS (8, 0)]
+#endif
 		IslamicTabular,
+#if !NET
 		[Mac (10, 10)]
 		[iOS (8, 0)]
+#endif
 		IslamicUmmAlQura,
 #pragma warning disable 612 // RepublicOfChina is obsolete
 		Taiwan = RepublicOfChina

src/Foundation/NSCoder.cs

@@ -28,6 +28,7 @@
 using System;
 using System.Collections.Generic;
 using System.Runtime.InteropServices;
+using System.Runtime.Versioning;
 using ObjCRuntime;
 
 namespace Foundation {
@@ -177,15 +178,19 @@ public bool TryDecode (string key, out byte [] result)
 			return false;
 		}
 
+#if !NET
 		[iOS (9,0), Mac (10,11)]
+#endif
 		public NSObject DecodeTopLevelObject (Type type, string key, out NSError error)
 		{
 			if (type == null)
 				throw new ArgumentNullException ("type");
 			return DecodeTopLevelObject (new Class (type), key, out error);
 		}
 
+#if !NET
 		[iOS (9,0), Mac (10,11)]
+#endif
 		public NSObject DecodeTopLevelObject (Type[] types, string key, out NSError error)
 		{
 			NSSet<Class> typeSet = null;

src/Foundation/NSExpression.cs

@@ -3,6 +3,7 @@
 //       tests for those was not possible. The properties for these two types have been deduced from the other types yet bugs are possible and an objc exception will be thrown.
 using System;
 using System.Runtime.InteropServices;
+using System.Runtime.Versioning;
 using ObjCRuntime;
 
 namespace Foundation {
@@ -92,7 +93,9 @@ public virtual NSExpression LeftExpression {
 			}
 		}
 
+#if !NET
 		[Mac(10,11),iOS(9,0)]
+#endif
 		[Export ("trueExpression")]
 		public virtual NSExpression TrueExpression {
 			get {
@@ -105,7 +108,9 @@ public virtual NSExpression TrueExpression {
 			}
 		}
 
+#if !NET
 		[Mac(10,11),iOS(9,0)]
+#endif
 		[Export ("falseExpression")]
 		public virtual NSExpression FalseExpression {
 			get {

src/Foundation/NSIndexPath.cs

@@ -11,6 +11,7 @@
 using System.Reflection;
 using System.Collections.Generic;
 using System.Runtime.InteropServices;
+using System.Runtime.Versioning;
 
 using ObjCRuntime;
 
@@ -71,7 +72,9 @@ public unsafe nuint [] GetIndexes ()
 			return ret;
 		}
 
+#if !NET
 		[iOS (9,0), Mac(10,11)]
+#endif
 		public unsafe nuint [] GetIndexes (NSRange range)
 		{
 			var ret = new nuint [range.Length];

src/Foundation/NSItemProvider.cs

@@ -2,6 +2,7 @@
 using System.Threading.Tasks;
 using CloudKit;
 using ObjCRuntime;
+using System.Runtime.Versioning;
 
 namespace Foundation 
 {
@@ -29,7 +30,12 @@ public virtual Task<CloudKitRegistrationPreparationHandler> RegisterCloudKitShar
 		}
 #endif
 
+#if !NET
 		[Watch (4,0), TV (11,0), Mac (10,13), iOS (11,0)]
+#else
+		[SupportedOSPlatform ("ios11.0")]
+		[SupportedOSPlatform ("tvos11.0")]
+#endif
 		public NSProgress LoadObject<T> (Action<T, NSError> completionHandler) where T: NSObject, INSItemProviderReading
 		{
 			return LoadObject (new Class (typeof (T)), (rv, err) =>
@@ -41,7 +47,12 @@ public NSProgress LoadObject<T> (Action<T, NSError> completionHandler) where T:
 			});
 		}
 
+#if !NET
 		[Watch (4,0), TV (11,0), Mac (10,13), iOS (11,0)]
+#else
+		[SupportedOSPlatform ("ios11.0")]
+		[SupportedOSPlatform ("tvos11.0")]
+#endif
 		public Task<T> LoadObjectAsync<T> () where T: NSObject, INSItemProviderReading
 		{
 			var rv = LoadObjectAsync (new Class (typeof (T)));
@@ -54,7 +65,12 @@ public Task<T> LoadObjectAsync<T> () where T: NSObject, INSItemProviderReading
 			});
 		}
 
+#if !NET
 		[Watch (4,0), TV (11,0), Mac (10,13), iOS (11,0)]
+#else
+		[SupportedOSPlatform ("ios11.0")]
+		[SupportedOSPlatform ("tvos11.0")]
+#endif
 		public Task<T> LoadObjectAsync<T> (out NSProgress result) where T: NSObject, INSItemProviderReading
 		{
 			var rv = LoadObjectAsync (new Class (typeof (T)), out result);