diff --git a/src/Mono.Android/Android.App/Dialog.cs b/src/Mono.Android/Android.App/Dialog.cs
index 94c40398b18..14f32f00bc1 100644
--- a/src/Mono.Android/Android.App/Dialog.cs
+++ b/src/Mono.Android/Android.App/Dialog.cs
@@ -1,5 +1,4 @@
 using System;
-using System.Diagnostics.CodeAnalysis;
 using Android.Runtime;
 
 namespace Android.App {
@@ -9,8 +8,7 @@ public partial class Dialog {
 		protected Dialog (Android.Content.Context context, bool cancelable, EventHandler cancelHandler) 
 			: this (context, cancelable, new Android.Content.IDialogInterfaceOnCancelListenerImplementor () { Handler = cancelHandler }) {}
 
-		[return: MaybeNull]
-		public T FindViewById<T> (int id)
+		public T? FindViewById<T> (int id)
 			where T : Android.Views.View
 		{
 			return this.FindViewById (id).JavaCast<T> ();
diff --git a/src/Mono.Android/Android.App/FragmentManager.cs b/src/Mono.Android/Android.App/FragmentManager.cs
index 8b67deecaa7..5d32da4a247 100644
--- a/src/Mono.Android/Android.App/FragmentManager.cs
+++ b/src/Mono.Android/Android.App/FragmentManager.cs
@@ -1,22 +1,18 @@
-using System.Diagnostics.CodeAnalysis;
 using Android.OS;
 using Android.Runtime;
 
 #if ANDROID_11
 namespace Android.App {
 	public partial class FragmentManager {
-		[return: MaybeNull]
-		public T FindFragmentById<T> (int id) where T : Fragment
+		public T? FindFragmentById<T> (int id) where T : Fragment
 		{
 			return FindFragmentById (id).JavaCast<T> ();
 		}
-		[return: MaybeNull]
-		public T FindFragmentByTag<T> (string tag) where T : Fragment
+		public T? FindFragmentByTag<T> (string tag) where T : Fragment
 		{
 			return FindFragmentByTag (tag).JavaCast<T> ();
 		}
-		[return: MaybeNull]
-		public T GetFragment<T> (Bundle bundle, string key) where T : Fragment
+		public T? GetFragment<T> (Bundle bundle, string key) where T : Fragment
 		{
 			return GetFragment (bundle, key).JavaCast<T> ();
 		}
diff --git a/src/Mono.Android/Android.Graphics/Color.cs b/src/Mono.Android/Android.Graphics/Color.cs
index 6b866cb4735..bf57968663c 100644
--- a/src/Mono.Android/Android.Graphics/Color.cs
+++ b/src/Mono.Android/Android.Graphics/Color.cs
@@ -416,7 +416,7 @@ public override void DestroyGenericArgumentState (Color value, ref JniValueMarsh
 
 		public override Expression CreateParameterToManagedExpression (JniValueMarshalerContext context, ParameterExpression sourceValue, ParameterAttributes synchronize, Type targetType)
 		{
-			var c = typeof (Color).GetConstructor (new[]{typeof (int)});
+			var c = typeof (Color).GetConstructor (new[]{typeof (int)})!;
 			var v = Expression.Variable (typeof (Color), sourceValue.Name + "_val");
 			context.LocalVariables.Add (v);
 			context.CreationStatements.Add (Expression.Assign (v, Expression.New (c, sourceValue)));
diff --git a/src/Mono.Android/Android.OS/AsyncTask.cs b/src/Mono.Android/Android.OS/AsyncTask.cs
index 772e2e69908..fe58a59c43b 100644
--- a/src/Mono.Android/Android.OS/AsyncTask.cs
+++ b/src/Mono.Android/Android.OS/AsyncTask.cs
@@ -88,9 +88,8 @@ public AsyncTask ()
 		}
 
 		static IntPtr id_get;
-		[return: MaybeNull]
 		[Register ("get", "()Ljava/lang/Object;", "")]
-		public TResult GetResult ()
+		public TResult? GetResult ()
 		{
 			if (id_get == IntPtr.Zero)
 				id_get = JNIEnv.GetMethodID (class_ref, "get", "()Ljava/lang/Object;");
diff --git a/src/Mono.Android/Android.Runtime/JNIEnv.cs b/src/Mono.Android/Android.Runtime/JNIEnv.cs
index 1b4c2430344..92ff8fe3a70 100644
--- a/src/Mono.Android/Android.Runtime/JNIEnv.cs
+++ b/src/Mono.Android/Android.Runtime/JNIEnv.cs
@@ -747,7 +747,7 @@ public static void CopyArray (IntPtr src, string[] dest)
 
 		static TValue GetConverter<TValue>(Dictionary<Type, TValue> dict, Type? elementType, IntPtr array)
 		{
-			TValue converter;
+			TValue? converter;
 
 			if (elementType != null) {
 				if (elementType.IsEnum)
diff --git a/src/Mono.Android/Android.Runtime/JavaCollection.cs b/src/Mono.Android/Android.Runtime/JavaCollection.cs
index de61c1c2dd7..70660bc24a3 100644
--- a/src/Mono.Android/Android.Runtime/JavaCollection.cs
+++ b/src/Mono.Android/Android.Runtime/JavaCollection.cs
@@ -386,8 +386,7 @@ System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator ()
 			return GetEnumerator ()!;
 		}
 
-		[return: MaybeNull]
-		public IEnumerator<T> GetEnumerator ()
+		public IEnumerator<T?> GetEnumerator ()
 		{
 			return System.Linq.Extensions.ToEnumerator_Dispose<T> (Iterator());
 		}
diff --git a/src/Mono.Android/Android.Runtime/JavaDictionary.cs b/src/Mono.Android/Android.Runtime/JavaDictionary.cs
index 773bd217530..80656dfc58c 100644
--- a/src/Mono.Android/Android.Runtime/JavaDictionary.cs
+++ b/src/Mono.Android/Android.Runtime/JavaDictionary.cs
@@ -444,8 +444,7 @@ public JavaDictionary (IDictionary<K, V> items) : this ()
 		//
 		//     https://developer.android.com/reference/java/util/Map#get(java.lang.Object)
 		//
-		[return: MaybeNull]
-		internal V Get (K key)
+		internal V? Get (K key)
 		{
 			if (id_get == IntPtr.Zero)
 				id_get = JNIEnv.GetMethodID (map_class, "get", "(Ljava/lang/Object;)Ljava/lang/Object;");
diff --git a/src/Mono.Android/Android.Runtime/JavaList.cs b/src/Mono.Android/Android.Runtime/JavaList.cs
index 6fb441fdba1..980b01f386e 100644
--- a/src/Mono.Android/Android.Runtime/JavaList.cs
+++ b/src/Mono.Android/Android.Runtime/JavaList.cs
@@ -727,8 +727,7 @@ public JavaList (IEnumerable<T> items) : this ()
 		//
 		//     https://developer.android.com/reference/java/util/List.html?hl=en#get(int)
 		//
-		[return: MaybeNull]
-		internal unsafe T InternalGet (int location)
+		internal unsafe T? InternalGet (int location)
 		{
 			const string id = "get.(I)Ljava/lang/Object;";
 			JniObjectReference obj;
@@ -880,8 +879,7 @@ System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator ()
 			return GetEnumerator ()!;
 		}
 
-		[return: MaybeNull]
-		public IEnumerator<T> GetEnumerator ()
+		public IEnumerator<T?> GetEnumerator ()
 		{
 			return System.Linq.Extensions.ToEnumerator_Dispose<T> (Iterator ());
 		}
diff --git a/src/Mono.Android/Android.Runtime/JavaSet.cs b/src/Mono.Android/Android.Runtime/JavaSet.cs
index 381877c44a0..c141e1058a4 100644
--- a/src/Mono.Android/Android.Runtime/JavaSet.cs
+++ b/src/Mono.Android/Android.Runtime/JavaSet.cs
@@ -390,7 +390,6 @@ System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator ()
 			return GetEnumerator ()!;
 		}
 
-		[return: MaybeNull]
 		public IEnumerator<T> GetEnumerator ()
 		{
 			return System.Linq.Extensions.ToEnumerator_Dispose<T> (Iterator ());
diff --git a/src/Mono.Android/Android.Runtime/XmlPullParserReader.cs b/src/Mono.Android/Android.Runtime/XmlPullParserReader.cs
index 72d18b90a08..5bda50595b2 100644
--- a/src/Mono.Android/Android.Runtime/XmlPullParserReader.cs
+++ b/src/Mono.Android/Android.Runtime/XmlPullParserReader.cs
@@ -72,7 +72,7 @@ public QName (XmlPullParserReader r, string name)
 			}
 			
 			public string LocalName;
-			public string Namespace;
+			public string? Namespace;
 		}
 		
 		public XmlPullParserReader (IJavaObject source)
@@ -140,7 +140,7 @@ public override bool EOF {
 				throw new ArgumentOutOfRangeException ();
 		}
 
-		public override string? GetAttribute (string localName, string namespaceName)
+		public override string? GetAttribute (string localName, string? namespaceName)
 		{
 			return namespaceName == xmlns_uri ? source.GetNamespace (localName) : source.GetAttributeValue (namespaceName, localName);
 		}
@@ -179,7 +179,7 @@ public override string? LocalName {
 			}
 		}
 
-		public override string LookupNamespace (string prefix)
+		public override string? LookupNamespace (string prefix)
 		{
 			return nsmgr.LookupNamespace (prefix);
 		}
@@ -192,7 +192,7 @@ public override void MoveToAttribute (int i)
 			attr_value = false;
 		}
 
-		public override bool MoveToAttribute (string localName, string namespaceName)
+		public override bool MoveToAttribute (string localName, string? namespaceName)
 		{
 			if (namespaceName == xmlns_uri) {
 				for (int i = 0; i < ns_count; i++)
@@ -251,7 +251,7 @@ public override string? Name {
 			get { return String.IsNullOrEmpty (Prefix) ? LocalName : Prefix + ':' + LocalName; }
 		}
 
-		public override XmlNameTable NameTable {
+		public override XmlNameTable? NameTable {
 			get { return nsmgr.NameTable; }
 		}
 
@@ -297,9 +297,14 @@ public override XmlNodeType NodeType {
 			}
 		}
 
-		public override string Prefix {
+		public override string? Prefix {
 			// getPrefix(), getAttributePrefix(), getNamespacePrefix() are not supported!!!
-			get { return nsmgr.LookupPrefix (NamespaceURI); }
+			get {
+				if (NamespaceURI is null)
+					return null;
+
+				return nsmgr.LookupPrefix (NamespaceURI);
+			}
 		}
 
 		public override bool Read ()
@@ -331,14 +336,14 @@ public override bool Read ()
 			if (wasEmptyElement || NodeType == XmlNodeType.EndElement)
 				nsmgr.PopScope ();
 			if (NodeType == XmlNodeType.Element) {
-				if (NamespaceURI != String.Empty && nsmgr.LookupPrefix (NamespaceURI) != String.Empty)
+				if (!string.IsNullOrEmpty (NamespaceURI) && nsmgr.LookupPrefix (NamespaceURI) != String.Empty)
 					nsmgr.AddNamespace (String.Empty, NamespaceURI);
 				else if (NamespaceURI == String.Empty && nsmgr.DefaultNamespace != String.Empty)
 					nsmgr.AddNamespace (String.Empty, String.Empty);
 				for (int i = 0; i < source.AttributeCount; i++) {
 					string? ns = source.GetAttributeNamespace (i);
-					if (ns != String.Empty && nsmgr.LookupPrefix (ns) == null)
-						nsmgr.AddNamespace ("p" + i, source.GetAttributeNamespace (i));
+					if (!string.IsNullOrEmpty (ns) && nsmgr.LookupPrefix (ns) == null)
+						nsmgr.AddNamespace ("p" + i, ns);
 				}
 				nsmgr.PushScope ();
 			}
diff --git a/src/Mono.Android/Android.Runtime/XmlReaderPullParser.cs b/src/Mono.Android/Android.Runtime/XmlReaderPullParser.cs
index ad19ae407da..4fcf755ce3f 100644
--- a/src/Mono.Android/Android.Runtime/XmlReaderPullParser.cs
+++ b/src/Mono.Android/Android.Runtime/XmlReaderPullParser.cs
@@ -111,11 +111,11 @@ public int GetIdAttributeResourceValue (int defaultValue)
 			return GetAttributeResourceValue (null, "id", defaultValue);
 		}
 	
-		public string ClassAttribute {
+		public string? ClassAttribute {
 			get { return GetAttributeValue (null, "class"); }
 		}
 	
-		public string IdAttribute {
+		public string? IdAttribute {
 			get { return GetAttributeValue (null, "id"); }
 		}
 	
@@ -181,8 +181,11 @@ public string GetAttributeValue (int index)
 			return r.GetAttribute (index);
 		}
 	
-		public string GetAttributeValue (string? namespaceURI, string? name)
+		public string? GetAttributeValue (string? namespaceURI, string? name)
 		{
+			if (name is null)
+				return null;
+
 			return r.GetAttribute (name, namespaceURI);
 		}
 	
@@ -196,7 +199,7 @@ public bool GetFeature (string? name)
 			return false;
 		}
 	
-		public string GetNamespace (string? prefix)
+		public string? GetNamespace (string prefix)
 		{
 			return r.LookupNamespace (prefix);
 		}
diff --git a/src/Mono.Android/Android.Telephony/CellInfo.cs b/src/Mono.Android/Android.Telephony/CellInfo.cs
index 66526a38dbb..c8b5d91ffda 100644
--- a/src/Mono.Android/Android.Telephony/CellInfo.cs
+++ b/src/Mono.Android/Android.Telephony/CellInfo.cs
@@ -9,7 +9,7 @@ namespace Android.Telephony {
 
 	public partial class CellInfo {
 
-		static Delegate cb_getCellIdentity;
+		static Delegate? cb_getCellIdentity;
 #pragma warning disable 0169
 		static Delegate GetGetCellIdentityHandler ()
 		{
@@ -20,7 +20,7 @@ static Delegate GetGetCellIdentityHandler ()
 
 		static IntPtr n_GetCellIdentity (IntPtr jnienv, IntPtr native__this)
 		{
-			Android.Telephony.CellInfo __this = global::Java.Lang.Object.GetObject<Android.Telephony.CellInfo> (jnienv, native__this, JniHandleOwnership.DoNotTransfer);
+			var __this = global::Java.Lang.Object.GetObject<Android.Telephony.CellInfo> (jnienv, native__this, JniHandleOwnership.DoNotTransfer)!;
 			return JNIEnv.ToLocalJniHandle (__this.CellIdentity);
 		}
 #pragma warning restore 0169
@@ -32,7 +32,7 @@ public unsafe virtual Android.Telephony.CellIdentity CellIdentity {
 				const string __id = "getCellIdentity.()Landroid/telephony/CellIdentity;";
 				try {
 					var __rm = _members.InstanceMethods.InvokeVirtualObjectMethod (__id, this, null);
-					return global::Java.Lang.Object.GetObject<Android.Telephony.CellIdentity> (__rm.Handle, JniHandleOwnership.TransferLocalRef);
+					return global::Java.Lang.Object.GetObject<Android.Telephony.CellIdentity> (__rm.Handle, JniHandleOwnership.TransferLocalRef)!;
 				}
 		                catch (Java.Lang.NoSuchMethodError) {
 					throw new Java.Lang.AbstractMethodError (__id);
@@ -40,7 +40,7 @@ public unsafe virtual Android.Telephony.CellIdentity CellIdentity {
 			}
 		}
 
-		static Delegate cb_getCellSignalStrength;
+		static Delegate? cb_getCellSignalStrength;
 #pragma warning disable 0169
 		static Delegate GetGetCellSignalStrengthHandler ()
 		{
@@ -51,7 +51,7 @@ static Delegate GetGetCellSignalStrengthHandler ()
 
 		static IntPtr n_GetCellSignalStrength (IntPtr jnienv, IntPtr native__this)
 		{
-			Android.Telephony.CellInfo __this = global::Java.Lang.Object.GetObject<Android.Telephony.CellInfo> (jnienv, native__this, JniHandleOwnership.DoNotTransfer);
+			var __this = global::Java.Lang.Object.GetObject<Android.Telephony.CellInfo> (jnienv, native__this, JniHandleOwnership.DoNotTransfer)!;
 			return JNIEnv.ToLocalJniHandle (__this.CellSignalStrength);
 		}
 #pragma warning restore 0169
@@ -63,7 +63,7 @@ public unsafe virtual Android.Telephony.CellSignalStrength CellSignalStrength {
 				const string __id = "getCellSignalStrength.()Landroid/telephony/CellSignalStrength;";
 				try {
 					var __rm = _members.InstanceMethods.InvokeVirtualObjectMethod (__id, this, null);
-					return global::Java.Lang.Object.GetObject<Android.Telephony.CellSignalStrength> (__rm.Handle, JniHandleOwnership.TransferLocalRef);
+					return global::Java.Lang.Object.GetObject<Android.Telephony.CellSignalStrength> (__rm.Handle, JniHandleOwnership.TransferLocalRef)!;
 				}
 				catch (Java.Lang.NoSuchMethodError) {
 					throw new Java.Lang.AbstractMethodError (__id);
diff --git a/src/Mono.Android/Android.Views/View.cs b/src/Mono.Android/Android.Views/View.cs
index 41ed43e6982..fdf7647cd03 100644
--- a/src/Mono.Android/Android.Views/View.cs
+++ b/src/Mono.Android/Android.Views/View.cs
@@ -22,8 +22,7 @@ public bool PerformAccessibilityAction (GlobalAction action, Bundle arguments)
 		}
 #endif
 
-		[return: MaybeNull]
-		public T FindViewById<T> (int id)
+		public T? FindViewById<T> (int id)
 			where T : Android.Views.View
 		{
 			return this.FindViewById (id).JavaCast<T> ();
diff --git a/src/Mono.Android/Android.Views/Window.cs b/src/Mono.Android/Android.Views/Window.cs
index a28ea6c1a07..6164a970d6a 100644
--- a/src/Mono.Android/Android.Views/Window.cs
+++ b/src/Mono.Android/Android.Views/Window.cs
@@ -6,8 +6,7 @@ namespace Android.Views {
 
 	partial class Window {
 
-		[return: MaybeNull]
-		public T FindViewById<T> (int id)
+		public T? FindViewById<T> (int id)
 			where T : Android.Views.View
 		{
 			return this.FindViewById (id).JavaCast<T> ();
diff --git a/src/Mono.Android/Android.Widget/ArrayAdapter.cs b/src/Mono.Android/Android.Widget/ArrayAdapter.cs
index f27e9caf885..cf35e67fc07 100644
--- a/src/Mono.Android/Android.Widget/ArrayAdapter.cs
+++ b/src/Mono.Android/Android.Widget/ArrayAdapter.cs
@@ -185,9 +185,8 @@ public void Add (T @object)
 		}
 
 		static IntPtr id_getItem_I;
-		[return: MaybeNull]
 		[Register ("getItem", "(I)Ljava/lang/Object;", "GetGetItem_IHandler")]
-		public T GetItem (int position)
+		public T? GetItem (int position)
 		{
 			if (id_getItem_I == IntPtr.Zero)
 				id_getItem_I = JNIEnv.GetMethodID (class_ref, "getItem", "(I)Ljava/lang/Object;");
diff --git a/src/Mono.Android/Java.Interop/JavaConvert.cs b/src/Mono.Android/Java.Interop/JavaConvert.cs
index 6f132b95bf3..678ead478b9 100644
--- a/src/Mono.Android/Java.Interop/JavaConvert.cs
+++ b/src/Mono.Android/Java.Interop/JavaConvert.cs
@@ -92,15 +92,13 @@ static Func<IntPtr, JniHandleOwnership, object> GetJniHandleConverterForType ([D
 					typeof (Func<IntPtr, JniHandleOwnership, object>), m);
 		}
 
-		[return: MaybeNull]
-		public static T FromJniHandle<T>(IntPtr handle, JniHandleOwnership transfer)
+		public static T? FromJniHandle<T>(IntPtr handle, JniHandleOwnership transfer)
 		{
 			bool set;
 			return FromJniHandle<T>(handle, transfer, out set);
 		}
 
-		[return: MaybeNull]
-		public static T FromJniHandle<T>(IntPtr handle, JniHandleOwnership transfer, out bool set)
+		public static T? FromJniHandle<T>(IntPtr handle, JniHandleOwnership transfer, out bool set)
 		{
 			if (handle == IntPtr.Zero) {
 				set = false;
@@ -109,7 +107,7 @@ public static T FromJniHandle<T>(IntPtr handle, JniHandleOwnership transfer, out
 
 			var interned = (IJavaObject?) Java.Lang.Object.PeekObject (handle);
 			if (interned != null) {
-				T r = FromJavaObject<T>(interned, out set);
+				T? r = FromJavaObject<T>(interned, out set);
 				if (set) {
 					JNIEnv.DeleteRef (handle, transfer);
 					return r;
@@ -119,12 +117,12 @@ public static T FromJniHandle<T>(IntPtr handle, JniHandleOwnership transfer, out
 			set = true;
 
 			if (typeof (IJavaObject).IsAssignableFrom (typeof (T)))
-				return (T) Java.Lang.Object._GetObject<T> (handle, transfer);
+				return (T?) Java.Lang.Object._GetObject<T> (handle, transfer);
 
 			var converter = GetJniHandleConverter (typeof (T)) ??
 				GetJniHandleConverter (GetTypeMapping (handle));
 			if (converter != null)
-				return (T) converter (handle, transfer);
+				return (T?) converter (handle, transfer);
 
 			var v = Java.Lang.Object.GetObject (handle, transfer);
 			if (v is T)
@@ -132,7 +130,7 @@ public static T FromJniHandle<T>(IntPtr handle, JniHandleOwnership transfer, out
 
 			// hail mary pass; perhaps there's a MCW which participates in normal
 			// .NET type conversion?
-			return (T) Convert.ChangeType (v, typeof (T), CultureInfo.InvariantCulture);
+			return (T?) Convert.ChangeType (v, typeof (T), CultureInfo.InvariantCulture);
 		}
 
 		public static object? FromJniHandle (IntPtr handle, JniHandleOwnership transfer, Type? targetType = null)
@@ -208,15 +206,13 @@ public static T FromJniHandle<T>(IntPtr handle, JniHandleOwnership transfer, out
 			return null;
 		}
 
-		[return: MaybeNull]
-		public static T FromJavaObject<T>(IJavaObject? value)
+		public static T? FromJavaObject<T>(IJavaObject? value)
 		{
 			bool set;
 			return FromJavaObject<T>(value, out set);
 		}
 
-		[return: MaybeNull]
-		public static T FromJavaObject<T>(IJavaObject? value, out bool set)
+		public static T? FromJavaObject<T>(IJavaObject? value, out bool set)
 		{
 			if (value == null) {
 				set = false;
@@ -244,7 +240,7 @@ public static T FromJavaObject<T>(IJavaObject? value, out bool set)
 			set = true;
 			var converter = GetJniHandleConverter (typeof (T));
 			if (converter != null)
-				return (T) converter (lrefValue, JniHandleOwnership.TransferLocalRef);
+				return (T?) converter (lrefValue, JniHandleOwnership.TransferLocalRef);
 			JNIEnv.DeleteLocalRef (lrefValue);
 			return (T) Convert.ChangeType (value, typeof (T), CultureInfo.InvariantCulture);
 		}
diff --git a/src/Mono.Android/Java.Interop/JavaObjectExtensions.cs b/src/Mono.Android/Java.Interop/JavaObjectExtensions.cs
index 0110165e1be..145633b7e55 100644
--- a/src/Mono.Android/Java.Interop/JavaObjectExtensions.cs
+++ b/src/Mono.Android/Java.Interop/JavaObjectExtensions.cs
@@ -52,8 +52,7 @@ public static JavaDictionary<K,V> ToInteroperableCollection<K,V> (this IDictiona
 			return _JavaCast<TResult> (instance);
 		}
 
-		[return: MaybeNull]
-		internal static TResult _JavaCast<TResult> (this IJavaObject? instance)
+		internal static TResult? _JavaCast<TResult> (this IJavaObject? instance)
 		{
 			if (instance == null)
 				return default (TResult);
@@ -69,7 +68,7 @@ internal static TResult _JavaCast<TResult> (this IJavaObject? instance)
 				return (TResult) CastClass (instance, resultType);
 			}
 			else if (resultType.IsInterface) {
-				return (TResult) Java.Lang.Object.GetObject (instance.Handle, JniHandleOwnership.DoNotTransfer, resultType);
+				return (TResult?) Java.Lang.Object.GetObject (instance.Handle, JniHandleOwnership.DoNotTransfer, resultType);
 			}
 			else
 				throw new NotSupportedException (FormattableString.Invariant ($"Unable to convert type '{instance.GetType ().FullName}' to '{resultType.FullName}'."));
diff --git a/src/Mono.Android/Java.Interop/TypeManager.cs b/src/Mono.Android/Java.Interop/TypeManager.cs
index 6d4556bf7a4..269eda87a48 100644
--- a/src/Mono.Android/Java.Interop/TypeManager.cs
+++ b/src/Mono.Android/Java.Interop/TypeManager.cs
@@ -7,6 +7,7 @@
 using Java.Interop.Tools.TypeNameMappings;
 
 using Android.Runtime;
+using System.Diagnostics.CodeAnalysis;
 
 namespace Java.Interop {
 
@@ -166,7 +167,7 @@ static void n_Activate (IntPtr jnienv, IntPtr jclass, IntPtr typename_ptr, IntPt
 		internal static void Activate (IntPtr jobject, ConstructorInfo cinfo, object? []? parms)
 		{
 			try {
-				var newobj = RuntimeHelpers.GetUninitializedObject (cinfo.DeclaringType);
+				var newobj = RuntimeHelpers.GetUninitializedObject (cinfo.DeclaringType!);
 				if (newobj is Java.Lang.Object o) {
 					o.handle = jobject;
 				} else if (newobj is Java.Lang.Throwable throwable) {
@@ -177,7 +178,7 @@ internal static void Activate (IntPtr jobject, ConstructorInfo cinfo, object? []
 				cinfo.Invoke (newobj, parms);
 			} catch (Exception e) {
 				var m = FormattableString.Invariant (
-					$"Could not activate JNI Handle 0x{jobject:x} (key_handle 0x{JNIEnv.IdentityHash (jobject):x}) of Java type '{JNIEnv.GetClassNameFromInstance (jobject)}' as managed type '{cinfo.DeclaringType.FullName}'.");
+					$"Could not activate JNI Handle 0x{jobject:x} (key_handle 0x{JNIEnv.IdentityHash (jobject):x}) of Java type '{JNIEnv.GetClassNameFromInstance (jobject)}' as managed type '{cinfo?.DeclaringType?.FullName}'.");
 				Logger.Log (LogLevel.Warn, "monodroid", m);
 				Logger.Log (LogLevel.Warn, "monodroid", CreateJavaLocationException ().ToString ());
 
@@ -238,7 +239,7 @@ static Exception CreateJavaLocationException ()
 			Type? type = null;
 			int ls = class_name.LastIndexOf ('/');
 			var package = ls >= 0 ? class_name.Substring (0, ls) : "";
-			if (packageLookup.TryGetValue (package, out var mappers)) {
+			if (packageLookup!.TryGetValue (package, out var mappers)) {
 				foreach (Converter<string, Type?> c in mappers) {
 					type = c (class_name);
 					if (type == null)
@@ -360,6 +361,7 @@ public static void RegisterType (string java_class, Type t)
 
 		static Dictionary<string, List<Converter<string, Type?>>>? packageLookup;
 
+		[MemberNotNull (nameof (packageLookup))]
 		static void LazyInitPackageLookup ()
 		{
 			if (packageLookup == null)
diff --git a/src/Mono.Android/Java.Lang/Object.cs b/src/Mono.Android/Java.Lang/Object.cs
index 01dde260fc5..1c9ffe12260 100644
--- a/src/Mono.Android/Java.Lang/Object.cs
+++ b/src/Mono.Android/Java.Lang/Object.cs
@@ -263,10 +263,9 @@ protected void SetHandle (IntPtr value, JniHandleOwnership transfer)
 			return peeked;
 		}
 
-		[return: MaybeNull]
-		internal static T PeekObject <T> (IntPtr handle)
+		internal static T? PeekObject <T> (IntPtr handle)
 		{
-			return (T)PeekObject (handle, typeof (T));
+			return (T?)PeekObject (handle, typeof (T));
 		}
 
 		public static T? GetObject<T> (IntPtr jnienv, IntPtr handle, JniHandleOwnership transfer)
@@ -282,13 +281,12 @@ protected void SetHandle (IntPtr value, JniHandleOwnership transfer)
 			return _GetObject<T>(handle, transfer);
 		}
 
-		[return: MaybeNull]
-		internal static T _GetObject<T> (IntPtr handle, JniHandleOwnership transfer)
+		internal static T? _GetObject<T> (IntPtr handle, JniHandleOwnership transfer)
 		{
 			if (handle == IntPtr.Zero)
 				return default (T);
 
-			return (T) GetObject (handle, transfer, typeof (T));
+			return (T?) GetObject (handle, transfer, typeof (T));
 		}
 
 		internal static IJavaPeerable? GetObject (IntPtr handle, JniHandleOwnership transfer, Type? type = null)
@@ -306,8 +304,7 @@ internal static T _GetObject<T> (IntPtr handle, JniHandleOwnership transfer)
 		}
 
 		[EditorBrowsable (EditorBrowsableState.Never)]
-		[return: MaybeNull]
-		public T[] ToArray<T>()
+		public T[]? ToArray<T>()
 		{
 			return JNIEnv.GetArray<T>(Handle);
 		}
diff --git a/src/Mono.Android/System.Drawing/PointConverter.cs b/src/Mono.Android/System.Drawing/PointConverter.cs
index 3c9d6c2acb6..0255e55c87e 100644
--- a/src/Mono.Android/System.Drawing/PointConverter.cs
+++ b/src/Mono.Android/System.Drawing/PointConverter.cs
@@ -62,7 +62,7 @@ public override bool CanConvertTo (ITypeDescriptorContext context,
 			return base.CanConvertTo (context, destinationType);
 		}
 
-		public override object ConvertFrom (ITypeDescriptorContext context,
+		public override object? ConvertFrom (ITypeDescriptorContext context,
 						    CultureInfo culture,
 						    object value)
 		{
@@ -77,7 +77,10 @@ public override object ConvertFrom (ITypeDescriptorContext context,
 			Int32Converter converter = new Int32Converter ();
 			int[] numSubs = new int[subs.Length];
 			for (int i = 0; i < numSubs.Length; i++) {
-				numSubs[i] = (int) converter.ConvertFromString (context, culture, subs[i]);
+				if (converter.ConvertFromString (context, culture, subs[i]) is int num)
+					numSubs[i] = num;
+				else
+					throw new ArgumentException ($"Could not parse string '{subs[i]}' as integer");
 			}
 
 			if (subs.Length != 2)
@@ -86,7 +89,7 @@ public override object ConvertFrom (ITypeDescriptorContext context,
 			return new Point (numSubs[0], numSubs[1]);
 		}
 
-		public override object ConvertTo (ITypeDescriptorContext context,
+		public override object? ConvertTo (ITypeDescriptorContext context,
 						  CultureInfo culture,
 						  object value,
 						  Type destinationType)
@@ -130,7 +133,7 @@ public override bool GetCreateInstanceSupported (ITypeDescriptorContext context)
 			return true;
 		}
 
-		public override PropertyDescriptorCollection GetProperties (
+		public override PropertyDescriptorCollection? GetProperties (
 							ITypeDescriptorContext context,
 							object value, Attribute[] attributes)
 		{
diff --git a/src/Mono.Android/System.Drawing/RectangleConverter.cs b/src/Mono.Android/System.Drawing/RectangleConverter.cs
index dae83bded0d..364784f495f 100644
--- a/src/Mono.Android/System.Drawing/RectangleConverter.cs
+++ b/src/Mono.Android/System.Drawing/RectangleConverter.cs
@@ -66,7 +66,7 @@ public override bool CanConvertTo (ITypeDescriptorContext context,
 			return base.CanConvertTo (context, destinationType);
 		}
 
-		public override object ConvertFrom (ITypeDescriptorContext context,
+		public override object? ConvertFrom (ITypeDescriptorContext context,
 						    CultureInfo culture,
 						    object value)
 		{
@@ -79,7 +79,10 @@ public override object ConvertFrom (ITypeDescriptorContext context,
 			Int32Converter converter = new Int32Converter ();
 			int[] numSubs = new int[subs.Length];
 			for (int i = 0; i < numSubs.Length; i++) {
-				numSubs[i] = (int) converter.ConvertFromString (context, culture, subs[i]);
+				if (converter.ConvertFromString (context, culture, subs[i]) is int num)
+					numSubs[i] = num;
+				else
+					throw new ArgumentException ($"Could not parse string '{subs[i]}' as integer");
 			}
 
 			if (subs.Length != 4)
@@ -88,7 +91,7 @@ public override object ConvertFrom (ITypeDescriptorContext context,
 			return new Rectangle (numSubs[0], numSubs[1], numSubs[2], numSubs[3]);
 		}
 
-		public override object ConvertTo (ITypeDescriptorContext context,
+		public override object? ConvertTo (ITypeDescriptorContext context,
 						  CultureInfo culture,
 						  object value,
 						  Type destinationType)
@@ -144,7 +147,7 @@ public override bool GetCreateInstanceSupported (ITypeDescriptorContext context)
 			return true;
 		}
 
-		public override PropertyDescriptorCollection GetProperties (
+		public override PropertyDescriptorCollection? GetProperties (
 							ITypeDescriptorContext context,
 							object value, Attribute[] attributes)
 		{
diff --git a/src/Mono.Android/System.Drawing/SizeConverter.cs b/src/Mono.Android/System.Drawing/SizeConverter.cs
index b3ae44fe2b8..53fe055733c 100644
--- a/src/Mono.Android/System.Drawing/SizeConverter.cs
+++ b/src/Mono.Android/System.Drawing/SizeConverter.cs
@@ -65,7 +65,7 @@ public override bool CanConvertTo (ITypeDescriptorContext context,
 			return base.CanConvertTo (context, destinationType);
 		}
 
-		public override object ConvertFrom (ITypeDescriptorContext context,
+		public override object? ConvertFrom (ITypeDescriptorContext context,
 						    CultureInfo culture,
 						    object value)
 		{
@@ -80,7 +80,10 @@ public override object ConvertFrom (ITypeDescriptorContext context,
 			Int32Converter converter = new Int32Converter ();
 			int[] numSubs = new int[subs.Length];
 			for (int i = 0; i < numSubs.Length; i++) {
-				numSubs[i] = (int) converter.ConvertFromString (context, culture, subs[i]);
+				if (converter.ConvertFromString (context, culture, subs[i]) is int num)
+					numSubs[i] = num;
+				else
+					throw new ArgumentException ($"Could not parse string '{subs[i]}' as integer");
 			}
 
 			if (subs.Length != 2)
@@ -89,7 +92,7 @@ public override object ConvertFrom (ITypeDescriptorContext context,
 			return new Size (numSubs[0], numSubs[1]);
 		}
 
-		public override object ConvertTo (ITypeDescriptorContext context,
+		public override object? ConvertTo (ITypeDescriptorContext context,
 						  CultureInfo culture,
 						  object value,
 						  Type destinationType)
@@ -132,7 +135,7 @@ public override bool GetCreateInstanceSupported (ITypeDescriptorContext context)
 			return true;
 		}
 
-		public override PropertyDescriptorCollection GetProperties (
+		public override PropertyDescriptorCollection? GetProperties (
 							ITypeDescriptorContext context,
 							object value, Attribute[] attributes)
 		{
diff --git a/src/Mono.Android/System.Drawing/SizeFConverter.cs b/src/Mono.Android/System.Drawing/SizeFConverter.cs
index 7f0164cbd4c..8933839fba2 100644
--- a/src/Mono.Android/System.Drawing/SizeFConverter.cs
+++ b/src/Mono.Android/System.Drawing/SizeFConverter.cs
@@ -66,7 +66,7 @@ public override bool CanConvertTo (ITypeDescriptorContext context, Type destinat
 			return base.CanConvertTo (context, destinationType);
 		}
 
-		public override object ConvertFrom (ITypeDescriptorContext context, CultureInfo culture, object value)
+		public override object? ConvertFrom (ITypeDescriptorContext context, CultureInfo culture, object value)
 		{
 			var s = value as string;
 			if (s == null)
@@ -77,7 +77,10 @@ public override object ConvertFrom (ITypeDescriptorContext context, CultureInfo
 			SingleConverter converter = new SingleConverter ();
 			float[] numSubs = new float[subs.Length];
 			for (int i = 0; i < numSubs.Length; i++) {
-				numSubs[i] = (float) converter.ConvertFromString (context, culture, subs[i]);
+				if (converter.ConvertFromString (context, culture, subs[i]) is float num)
+					numSubs[i] = num;
+				else
+					throw new ArgumentException ($"Could not parse string '{subs[i]}' as float");
 			}
 
 			if (subs.Length != 2)
@@ -87,7 +90,7 @@ public override object ConvertFrom (ITypeDescriptorContext context, CultureInfo
 
 		}
 
-		public override object ConvertTo (ITypeDescriptorContext context, CultureInfo culture, object value, Type destinationType)
+		public override object? ConvertTo (ITypeDescriptorContext context, CultureInfo culture, object value, Type destinationType)
 		{
 			if (value is SizeF) {
 				SizeF size = (SizeF) value;
@@ -115,7 +118,7 @@ public override bool GetCreateInstanceSupported (ITypeDescriptorContext context)
 			return true;
 		}
 
-		public override PropertyDescriptorCollection GetProperties (ITypeDescriptorContext context, object value, Attribute[] attributes)
+		public override PropertyDescriptorCollection? GetProperties (ITypeDescriptorContext context, object value, Attribute[] attributes)
 		{
 			if (value is SizeF)
 				return TypeDescriptor.GetProperties (value, attributes);
diff --git a/src/Mono.Android/System.Linq/Extensions.cs b/src/Mono.Android/System.Linq/Extensions.cs
index bdb36cb09e1..ac555e17949 100644
--- a/src/Mono.Android/System.Linq/Extensions.cs
+++ b/src/Mono.Android/System.Linq/Extensions.cs
@@ -40,8 +40,7 @@ internal static IEnumerator ToEnumerator_Dispose (this Java.Util.IIterator sourc
 				}
 		}
 
-		[return: MaybeNull]
-		public static IEnumerable<T> ToEnumerable<T> (this Java.Lang.IIterable source)
+		public static IEnumerable<T?> ToEnumerable<T> (this Java.Lang.IIterable source)
 		{
 			if (source == null)
 				throw new ArgumentNullException ("source");
@@ -53,7 +52,6 @@ public static IEnumerable<T> ToEnumerable<T> (this Java.Lang.IIterable source)
 				}
 		}
 
-		[return: MaybeNull]
 		internal static IEnumerator<T> ToEnumerator_Dispose<T> (this Java.Util.IIterator source)
 		{
 			using (source)
diff --git a/src/Mono.Android/Xamarin.Android.Net/AndroidClientHandler.cs b/src/Mono.Android/Xamarin.Android.Net/AndroidClientHandler.cs
index a641d1cdc8b..83e858e1a62 100644
--- a/src/Mono.Android/Xamarin.Android.Net/AndroidClientHandler.cs
+++ b/src/Mono.Android/Xamarin.Android.Net/AndroidClientHandler.cs
@@ -310,7 +310,7 @@ protected virtual Task SetupRequest (HttpRequestMessage request, HttpURLConnecti
 		}
 
 		[DynamicDependency (DynamicallyAccessedMemberTypes.PublicParameterlessConstructor, typeof (AndroidMessageHandler))]
-		object GetUnderlyingHandler ()
+		object? GetUnderlyingHandler ()
 		{
 			var fieldName = "_nativeHandler";
 			FieldInfo? field = null;
diff --git a/src/Mono.Android/Xamarin.Android.Net/AndroidMessageHandler.cs b/src/Mono.Android/Xamarin.Android.Net/AndroidMessageHandler.cs
index 7d42441c66e..6804db9ced1 100644
--- a/src/Mono.Android/Xamarin.Android.Net/AndroidMessageHandler.cs
+++ b/src/Mono.Android/Xamarin.Android.Net/AndroidMessageHandler.cs
@@ -133,7 +133,7 @@ public void Reset ()
 			new AuthModuleDigest ()
 		};
 
-		CookieContainer _cookieContainer;
+		CookieContainer? _cookieContainer;
 		DecompressionMethods _decompressionMethods;
 
 		bool disposed;
@@ -183,9 +183,9 @@ public CookieContainer CookieContainer
 
 		public ClientCertificateOption ClientCertificateOptions { get; set; }
 
-		public X509CertificateCollection ClientCertificates { get; set; }
+		public X509CertificateCollection? ClientCertificates { get; set; }
 
-		public ICredentials DefaultProxyCredentials { get; set; }
+		public ICredentials? DefaultProxyCredentials { get; set; }
 
 		public int MaxConnectionsPerServer { get; set; } = int.MaxValue;
 
@@ -214,7 +214,7 @@ public CookieContainer CookieContainer
 			(int)Build.VERSION.SdkInt >= 29 ?
 				SslProtocols.Tls13 | SslProtocols.Tls12 : SslProtocols.Tls12;
 
-		public IDictionary<string, object?> Properties { get; set; }
+		public IDictionary<string, object?>? Properties { get; set; }
 
 		int maxAutomaticRedirections = 50;
 
@@ -398,7 +398,7 @@ string EncodeUrl (Uri url)
 		}
 
 #if !MONOANDROID1_0
-		async Task <HttpResponseMessage?> SendWithNegotiateAuthenticationAsync (HttpRequestMessage request, CancellationToken cancellationToken)
+		async Task <HttpResponseMessage> SendWithNegotiateAuthenticationAsync (HttpRequestMessage request, CancellationToken cancellationToken)
 		{
 			var response = await DoSendAsync (request, cancellationToken).ConfigureAwait (false);
 
@@ -418,7 +418,7 @@ string EncodeUrl (Uri url)
 			if (request == null)
 				throw new ArgumentNullException (nameof (request));
 
-			if (!request.RequestUri.IsAbsoluteUri)
+			if (request.RequestUri is null || !request.RequestUri.IsAbsoluteUri)
 				throw new ArgumentException ("Must represent an absolute URI", "request");
 
 			var redirectState = new RequestRedirectionState {
@@ -484,7 +484,7 @@ string EncodeUrl (Uri url)
 				return proxy;
 			}
 
-			Uri puri = Proxy.GetProxy (destination);
+			Uri? puri = Proxy.GetProxy (destination);
 			if (puri == null) {
 				return proxy;
 			}
@@ -540,6 +540,9 @@ Task ConnectAsync (HttpURLConnection httpConnection, CancellationToken ct)
 
 		protected virtual async Task WriteRequestContentToOutput (HttpRequestMessage request, HttpURLConnection httpConnection, CancellationToken cancellationToken)
 		{
+			if (request.Content is null)
+				return;
+
 			using (var stream = await request.Content.ReadAsStreamAsync ().ConfigureAwait (false)) {
 				await stream.CopyToAsync(httpConnection.OutputStream!, 4096, cancellationToken).ConfigureAwait(false);
 
@@ -738,7 +741,7 @@ Stream GetDecompressionWrapper (URLConnection httpConnection, Stream inputStream
 				return inputStream;
 			}
 
-			var encodings = new HashSet<string> (httpConnection.ContentEncoding?.Split (','), StringComparer.OrdinalIgnoreCase);
+			var encodings = new HashSet<string> (httpConnection.ContentEncoding.Split (','), StringComparer.OrdinalIgnoreCase);
 			Stream? ret = null;
 			string? supportedEncoding = null;
 			if (encodings.Contains (GZIP_ENCODING)) {
@@ -924,8 +927,7 @@ AuthenticationScheme GetAuthScheme (string scheme)
 
 		void ParseCookies (AndroidHttpResponseMessage ret, Uri connectionUri)
 		{
-			IEnumerable <string> cookieHeaderValue;
-			if (!UseCookies || CookieContainer == null || !ret.Headers.TryGetValues ("Set-Cookie", out cookieHeaderValue) || cookieHeaderValue == null) {
+			if (!UseCookies || CookieContainer == null || !ret.Headers.TryGetValues ("Set-Cookie", out var cookieHeaderValue) || cookieHeaderValue == null) {
 				if (Logger.LogNet)
 					Logger.Log (LogLevel.Info, LOG_APP, $"No cookies");
 				return;
@@ -1114,7 +1116,7 @@ void AppendEncoding (string encoding, ref List <string>? list)
 			if (accept_encoding?.Count > 0)
 				httpConnection.SetRequestProperty ("Accept-Encoding", String.Join (",", accept_encoding));
 
-			if (UseCookies && CookieContainer != null) {
+			if (UseCookies && CookieContainer != null && request.RequestUri is not null) {
 				string cookieHeaderValue = CookieContainer.GetCookieHeader (request.RequestUri);
 				if (!String.IsNullOrEmpty (cookieHeaderValue))
 					httpConnection.SetRequestProperty ("Cookie", cookieHeaderValue);
diff --git a/src/Mono.Android/Xamarin.Android.Net/AuthDigestSession.cs b/src/Mono.Android/Xamarin.Android.Net/AuthDigestSession.cs
index 4fb5f1ff3cc..e099c98095f 100644
--- a/src/Mono.Android/Xamarin.Android.Net/AuthDigestSession.cs
+++ b/src/Mono.Android/Xamarin.Android.Net/AuthDigestSession.cs
@@ -138,7 +138,7 @@ public bool Parse (string challenge)
 
 			lastUse = DateTime.Now;
 			var uri = new Uri (request.URL?.ToString ()!);
-			NetworkCredential cred = credentials.GetCredential (uri, "digest");
+			NetworkCredential? cred = credentials.GetCredential (uri, "digest");
 			if (cred == null)
 				return null;
 
diff --git a/src/Mono.Android/Xamarin.Android.Net/AuthModuleBasic.cs b/src/Mono.Android/Xamarin.Android.Net/AuthModuleBasic.cs
index 92052d41eb9..ec8813a1d40 100644
--- a/src/Mono.Android/Xamarin.Android.Net/AuthModuleBasic.cs
+++ b/src/Mono.Android/Xamarin.Android.Net/AuthModuleBasic.cs
@@ -34,7 +34,7 @@ sealed class AuthModuleBasic : IAndroidAuthenticationModule
 			if (request == null || credentials == null)
 				return null;
 
-			NetworkCredential cred = credentials.GetCredential (new Uri (request.URL?.ToString ()!), AuthenticationType.ToLowerInvariant ());
+			NetworkCredential? cred = credentials.GetCredential (new Uri (request.URL?.ToString ()!), AuthenticationType.ToLowerInvariant ());
 			if (cred == null)
 				return null;
 
diff --git a/src/Mono.Android/Xamarin.Android.Net/NegotiateAuthenticationHelper.cs b/src/Mono.Android/Xamarin.Android.Net/NegotiateAuthenticationHelper.cs
index de025c7b4fd..55641a649de 100644
--- a/src/Mono.Android/Xamarin.Android.Net/NegotiateAuthenticationHelper.cs
+++ b/src/Mono.Android/Xamarin.Android.Net/NegotiateAuthenticationHelper.cs
@@ -18,9 +18,9 @@ internal static class NegotiateAuthenticationHelper
 
 		internal class RequestedNegotiateAuthenticationData
 		{
-			public string AuthType { get; init; }
+			public required string AuthType { get; init; }
 			public bool IsProxyAuth { get; init; }
-			public NetworkCredential Credential { get; init; }
+			public required NetworkCredential Credential { get; init; }
 		}
 
 		internal static bool RequestNeedsNegotiateAuthentication (
diff --git a/src/Mono.Android/Xamarin.Android.Net/ServerCertificateCustomValidator.cs b/src/Mono.Android/Xamarin.Android.Net/ServerCertificateCustomValidator.cs
index e9201280b3a..ac6cb91d599 100644
--- a/src/Mono.Android/Xamarin.Android.Net/ServerCertificateCustomValidator.cs
+++ b/src/Mono.Android/Xamarin.Android.Net/ServerCertificateCustomValidator.cs
@@ -74,10 +74,10 @@ public void CheckServerTrusted (JavaX509Certificate[] javaChain, string authType
 			}
 
 			public void CheckClientTrusted (JavaX509Certificate[] chain, string authType)
-				=> _internalTrustManager.CheckClientTrusted (chain, authType);
+				=> _internalTrustManager?.CheckClientTrusted (chain, authType);
 
 			public JavaX509Certificate[] GetAcceptedIssuers ()
-				=> _internalTrustManager.GetAcceptedIssuers () ?? Array.Empty<JavaX509Certificate> ();
+				=> _internalTrustManager?.GetAcceptedIssuers () ?? Array.Empty<JavaX509Certificate> ();
 
 			private bool VerifyHostname (JavaX509Certificate[] javaChain)
 			{
@@ -158,8 +158,11 @@ private sealed class AlwaysAcceptingHostnameVerifier : Java.Lang.Object, IHostna
 			public bool Verify (string? hostname, ISSLSession? session) => true;
 		}
 
-		private static IX509TrustManager? FindX509TrustManager(ITrustManager[] trustManagers)
+		private static IX509TrustManager? FindX509TrustManager(ITrustManager[]? trustManagers)
 		{
+			if (trustManagers is null)
+				return null;
+
 			foreach (var trustManager in trustManagers) {
 				if (trustManager is IX509TrustManager tm)
 					return tm;