[release/10.0.1xx-preview5] [SystemConfiguration] Fix accidental break in NetworkReachability.Schedule|Unschedule. (#22914)

Fixes dotnet/maui#29678.

Backport of #22912.

Author: rolfbjarne

src/SystemConfiguration/NetworkReachability.cs

@@ -576,7 +576,7 @@ public bool Schedule (CFRunLoop runLoop, string mode)
 			if (mode is null)
 				ObjCRuntime.ThrowHelper.ThrowArgumentNullException (nameof (mode));
 
-			using var modeHandle = new TransientString (mode);
+			using var modeHandle = new TransientCFString (mode);
 			bool result = SCNetworkReachabilityScheduleWithRunLoop (Handle, runLoop.GetCheckedHandle (), modeHandle) != 0;
 			GC.KeepAlive (runLoop);
 			return result;
@@ -629,7 +629,7 @@ public bool Unschedule (CFRunLoop runLoop, string mode)
 			if (mode is null)
 				ObjCRuntime.ThrowHelper.ThrowArgumentNullException (nameof (mode));
 
-			using var modeHandle = new TransientString (mode);
+			using var modeHandle = new TransientCFString (mode);
 			bool result = SCNetworkReachabilityUnscheduleFromRunLoop (Handle, runLoop.GetCheckedHandle (), modeHandle) != 0;
 			GC.KeepAlive (runLoop);
 			return result;

tests/monotouch-test/SystemConfiguration/NetworkReachabilityTest.cs

@@ -8,6 +8,7 @@
 //
 
 using System;
+using CoreFoundation;
 using Foundation;
 #if !MONOMAC
 using UIKit;
@@ -137,5 +138,14 @@ public void Ctor_Invalid ()
 			} catch (ArgumentException) {
 			}
 		}
+
+		[Test]
+		public void Schedule ()
+		{
+			var ip = new IPAddress (0);
+			using var defaultRouteReachability = new NetworkReachability (ip);
+			Assert.IsTrue (defaultRouteReachability.Schedule (CFRunLoop.Main, CFRunLoop.ModeDefault), "Schedule");
+			Assert.IsTrue (defaultRouteReachability.Unschedule (CFRunLoop.Main, CFRunLoop.ModeDefault), "Unschedule");
+		}
 	}
 }