Make changes as per reviews.

Author: mandel-macaque

src/AudioUnit/AudioComponent.cs

@@ -55,20 +55,30 @@ public ResourceUsageInfo (NSDictionary dic) : base (dic) {}
 		public string[] IOKitUserClient { 
 			get {
 				var array = GetNativeValue<NSArray> (userClientK);
-				return NSArray.StringArrayFromHandle (array.ClassHandle);
+				if (array == null )
+					return null;
+				return NSArray.StringArrayFromHandle (array.Handle);
 			} 
 			set {
-				SetArrayValue (userClientK, value);
+				if (value == null)
+					SetArrayValue (userClientK, value);
+				else
+					RemoveValue (userClientK);
 			}
 		}
 
 		public string[] MachLookUpGlobalName { 
 			get {
 				var array = GetNativeValue<NSArray> (globalNameK);
-				return NSArray.StringArrayFromHandle (array.ClassHandle);
+				if (array == null)
+					return null;
+				return NSArray.StringArrayFromHandle (array.Handle);
 			} 
 			set {
-				SetArrayValue (globalNameK, value);
+				if (value == null)
+					SetArrayValue (globalNameK, value);
+				else
+					RemoveValue (globalNameK);	
 			}
 		}
 
@@ -176,17 +186,22 @@ public ResourceUsageInfo ResourceUsage {
 				return GetStrongDictionary<ResourceUsageInfo> (resourceUsageK);
 			} 
 			set {
-				SetNativeValue (resourceUsageK, value.Dictionary, true);
+				SetNativeValue (resourceUsageK, value?.Dictionary, true);
 			}
 		}
 
 		public string[] Tags { 
 			get {
 				var array = GetNativeValue<NSArray> (tagsK);
-				return NSArray.StringArrayFromHandle (array.ClassHandle);
+				if (array == null)
+					return null;
+				return NSArray.StringArrayFromHandle (array.Handle);
 			} 
 			set {
-				SetArrayValue (tagsK, value);
+				if (value == null)
+					RemoveValue (tagsK);	
+				else
+					SetArrayValue (tagsK, value);
 			}
 		}
 	}

src/AudioUnit/AudioUnit.cs

@@ -389,7 +389,7 @@ public struct RampStruct
 			[StructLayout (LayoutKind.Sequential)]
 			public struct ImmediateStruct
 			{
-				public uint bBufferOffset;
+				public uint BufferOffset;
 				public float Value;
 			}
 

tests/monotouch-test/AudioToolbox/AudioComponentTest.cs

@@ -52,6 +52,43 @@ public void GetSetComponentList ()
 				Assert.Throws <InvalidOperationException> (() => component.ComponentList = l);
 			}
 		}
+		
+		// test the diff properties of the ResourceUsageInfo since it was manually done
+		
+		[Test]
+		public void TestResourceUsageInfoIOKitUserClient ()
+		{
+			TestRuntime.AssertXcodeVersion (9, 0);
+			var clientId = "CustomUserClient1";
+			var resources = new ResourceUsageInfo ();
+			resources.IOKitUserClient = new string[] { clientId };
+			var userClientList = resources.IOKitUserClient;
+			Assert.AreEqual (1, userClientList.Length, "List does not have all client ids.");
+			Assert.AreEqual (clientId, userClientList [0], "Client ids are not the same.");
+
+			// similar test but with null values.
+			
+			resources.IOKitUserClient = null;
+			Assert.IsNull (resources.IOKitUserClient, "Value was not set to null.");
+		}
+		
+		[Test]
+		public void TestResourceUsageInfoMachLookUpGlobalName ()
+		{
+			TestRuntime.AssertXcodeVersion (9, 0);
+			var serviceName = "MachServiceName1";
+			var resources = new ResourceUsageInfo ();
+			resources.MachLookUpGlobalName = new string[] { serviceName };
+			var serviceNames = resources.MachLookUpGlobalName;
+			
+			Assert.AreEqual (1, serviceNames.Length, "List does not have all service names.");
+			Assert.AreEqual (serviceName, serviceNames [0], "Service names are not equal.");
+
+			// similar test but with null values
+			
+			resources.MachLookUpGlobalName = null;
+			Assert.IsNull (resources.MachLookUpGlobalName, "Value was no set to null.");
+		}
 	}
 }