diff --git a/Ical.Net.Tests/EncodingProviderTests.cs b/Ical.Net.Tests/EncodingProviderTests.cs
index f25312c98..b32cc36cf 100644
--- a/Ical.Net.Tests/EncodingProviderTests.cs
+++ b/Ical.Net.Tests/EncodingProviderTests.cs
@@ -5,6 +5,7 @@
 
 #nullable enable
 using System;
+using System.Runtime.Serialization;
 using Ical.Net.Serialization;
 using NUnit.Framework;
 using EncodingProvider = Ical.Net.Serialization.EncodingProvider;
@@ -33,7 +34,7 @@ public void Encode_ShouldBeNull_WhenInvalidEncodingIsProvided()
         const string encoding = "Invalid-Encoding";
         var data = "Hello"u8.ToArray();
 
-        Assert.That(GetEncodingProvider().Encode(encoding, data), Is.Null);
+        Assert.That(() => GetEncodingProvider().Encode(encoding, data), Throws.TypeOf<SerializationException>());
     }
 
     [Test]
@@ -53,7 +54,7 @@ public void Decode_ShouldBeNull_WhenInvalidEncodingIsProvided()
         const string encoding = "Invalid-Encoding";
         const string data = "Hello";
 
-        Assert.That(GetEncodingProvider().DecodeString(encoding, data), Is.Null);
+        Assert.That(() => GetEncodingProvider().DecodeString(encoding, data), Throws.TypeOf<SerializationException>());
     }
 
     [Test]
diff --git a/Ical.Net.Tests/PeriodListWrapperTests.cs b/Ical.Net.Tests/PeriodListWrapperTests.cs
index d6f5c8a0f..995d392f1 100644
--- a/Ical.Net.Tests/PeriodListWrapperTests.cs
+++ b/Ical.Net.Tests/PeriodListWrapperTests.cs
@@ -185,7 +185,7 @@ public void AddRPeriod_ShouldCreate_DedicatePeriodList()
         ]);
 
         var serializer = new CalendarSerializer(cal);
-        var serialized = serializer.SerializeToString();
+        var serialized = serializer.SerializeToString()!;
         // Assign the deserialized event
         cal = Calendar.Load(serialized)!;
         evt = cal.Events[0];
diff --git a/Ical.Net.Tests/RecurrenceTests.cs b/Ical.Net.Tests/RecurrenceTests.cs
index b573aae01..fe535597c 100644
--- a/Ical.Net.Tests/RecurrenceTests.cs
+++ b/Ical.Net.Tests/RecurrenceTests.cs
@@ -3940,7 +3940,7 @@ public void TestDtStartTimezone(string? tzId)
     [TestCase(1, TestMaxIncrementCountWithoutGaps, false)]
     public void TestMaxIncrementCount(int? limit, string ical, bool expectException)
     {
-        var cal = Calendar.Load(ical);
+        var cal = Calendar.Load(ical)!;
 
         var options = new EvaluationOptions
         {
diff --git a/Ical.Net.Tests/RecurrenceWithExDateTests.cs b/Ical.Net.Tests/RecurrenceWithExDateTests.cs
index 160bfce06..706ab55f3 100644
--- a/Ical.Net.Tests/RecurrenceWithExDateTests.cs
+++ b/Ical.Net.Tests/RecurrenceWithExDateTests.cs
@@ -55,7 +55,7 @@ public void ShouldNotOccurOnLocalExceptionDate(bool useExDateWithTime)
 
         // Act
         var serializer = new CalendarSerializer();
-        var ics = serializer.SerializeToString(calendar);
+        var ics = serializer.SerializeToString(calendar)!;
 
         var deserializedCalendar = Calendar.Load(ics)!;
         var occurrences = deserializedCalendar.GetOccurrences<CalendarEvent>().ToList();
@@ -102,7 +102,7 @@ public void ShouldNotOccurOnUtcExceptionDate()
         var serializer = new CalendarSerializer();
         ics = serializer.SerializeToString(cal);
         // serialize and deserialize to ensure the exclusion dates de/serialized
-        cal = Calendar.Load(new CalendarSerializer(cal).SerializeToString())!;
+        cal = Calendar.Load(new CalendarSerializer(cal).SerializeToString()!)!;
 
         // Start date: 2024-10-19 at 18:00 (GMT Standard Time)
         // Recurrence: Every hour, 4 occurrences
@@ -150,7 +150,7 @@ public void MultipleExclusionDatesSameTimeZoneShouldBeExcluded()
         var serializer = new CalendarSerializer();
         ics = serializer.SerializeToString(cal);
         // serialize and deserialize to ensure the exclusion dates de/serialized
-        cal = Calendar.Load(new CalendarSerializer(cal).SerializeToString())!;
+        cal = Calendar.Load(new CalendarSerializer(cal).SerializeToString()!)!;
 
         // Occurrences:
         // 2023-10-25 09:00 (UTC Offset: +0200)
@@ -206,7 +206,7 @@ public void MultipleExclusionDatesDifferentZoneShouldBeExcluded()
 
         var cal = Calendar.Load(ics)!;
         // serialize and deserialize to ensure the exclusion dates de/serialized
-        cal = Calendar.Load(new CalendarSerializer(cal).SerializeToString())!;
+        cal = Calendar.Load(new CalendarSerializer(cal).SerializeToString()!)!;
         var occurrences = cal.GetOccurrences<CalendarEvent>().ToList();
 
         // Occurrences:
diff --git a/Ical.Net/Calendar.cs b/Ical.Net/Calendar.cs
index 7f9be70bd..446250751 100644
--- a/Ical.Net/Calendar.cs
+++ b/Ical.Net/Calendar.cs
@@ -121,7 +121,7 @@ public override int GetHashCode()
     {
         unchecked
         {
-            var hashCode = Name?.GetHashCode() ?? 0;
+            var hashCode = Name.GetHashCode();
             hashCode = (hashCode * 397) ^ CollectionHelpers.GetHashCode(UniqueComponents);
             hashCode = (hashCode * 397) ^ CollectionHelpers.GetHashCode(Events);
             hashCode = (hashCode * 397) ^ CollectionHelpers.GetHashCode(Todos);
@@ -227,7 +227,7 @@ public virtual IEnumerable<Occurrence> GetOccurrences<T>(CalDateTime? startTime
         // These are the UID/RECURRENCE-ID combinations that replace other occurrences.
         var recurrenceIdsAndUids = this.Children.OfType<IRecurrable>()
             .Where(r => r.RecurrenceId != null)
-            .Select(r => new { (r as IUniqueComponent).Uid, Dt = r.RecurrenceId!.Value })
+            .Select(r => new { (r as IUniqueComponent)?.Uid, Dt = r.RecurrenceId!.Value })
             .Where(r => r.Uid != null)
             .ToDictionary(x => x);
 
@@ -290,14 +290,12 @@ public virtual void MergeWith(IMergeable obj)
             return;
         }
 
-        Name ??= c.Name;
-
         Method = c.Method;
         Version = c.Version;
         ProductId = c.ProductId;
         Scale = c.Scale;
 
-        foreach (var p in c.Properties.Where(p => p.Name != null && !Properties.ContainsKey(p.Name)))
+        foreach (var p in c.Properties.Where(p => !Properties.ContainsKey(p.Name)))
         {
             Properties.Add(p);
         }
diff --git a/Ical.Net/CalendarCollection.cs b/Ical.Net/CalendarCollection.cs
index 5d14c1811..c61672a51 100644
--- a/Ical.Net/CalendarCollection.cs
+++ b/Ical.Net/CalendarCollection.cs
@@ -74,7 +74,7 @@ private FreeBusy CombineFreeBusy(FreeBusy? main, FreeBusy current)
         return this.Aggregate<Calendar, FreeBusy?>(null, (current, iCal) =>
         {
             var freeBusy = iCal.GetFreeBusy(freeBusyRequest);
-            return current is null ? freeBusy : CombineFreeBusy(current, freeBusy);
+            return current is null || freeBusy is null ? freeBusy : CombineFreeBusy(current, freeBusy);
         });
     }
 
@@ -83,7 +83,7 @@ private FreeBusy CombineFreeBusy(FreeBusy? main, FreeBusy current)
         return this.Aggregate<Calendar, FreeBusy?>(null, (current, iCal) =>
         {
             var freeBusy = iCal.GetFreeBusy(organizer, contacts, fromInclusive, toExclusive);
-            return current is null ? freeBusy : CombineFreeBusy(current, freeBusy);
+            return current is null || freeBusy is null ? freeBusy : CombineFreeBusy(current, freeBusy);
         });
     }
 
diff --git a/Ical.Net/CalendarComponents/Alarm.cs b/Ical.Net/CalendarComponents/Alarm.cs
index 56bfc47cd..698371470 100644
--- a/Ical.Net/CalendarComponents/Alarm.cs
+++ b/Ical.Net/CalendarComponents/Alarm.cs
@@ -172,7 +172,7 @@ private void AddRepeatedItems(List<AlarmOccurrence> occurrences)
         for (var i = 0; i < len; i++)
         {
             var ao = occurrences[i];
-            if (ao?.DateTime == null || ao.Component == null)
+            if (ao.DateTime == null || ao.Component == null)
             {
                 continue;
             }
diff --git a/Ical.Net/CalendarComponents/Todo.cs b/Ical.Net/CalendarComponents/Todo.cs
index 03d66a819..71d26f199 100644
--- a/Ical.Net/CalendarComponents/Todo.cs
+++ b/Ical.Net/CalendarComponents/Todo.cs
@@ -85,7 +85,7 @@ public virtual int PercentComplete
     public virtual IList<string> Resources
     {
         get => Properties.GetMany<string>("RESOURCES");
-        set => Properties.Set("RESOURCES", value ?? new List<string>());
+        set => Properties.Set("RESOURCES", value);
     }
 
     /// <summary>
diff --git a/Ical.Net/CalendarComponents/VTimeZone.cs b/Ical.Net/CalendarComponents/VTimeZone.cs
index df55547d0..5c502feb4 100644
--- a/Ical.Net/CalendarComponents/VTimeZone.cs
+++ b/Ical.Net/CalendarComponents/VTimeZone.cs
@@ -383,7 +383,7 @@ public override int GetHashCode()
     {
         unchecked
         {
-            var hashCode = Name?.GetHashCode() ?? 0;
+            var hashCode = Name.GetHashCode();
             hashCode = (hashCode * 397) ^ (TzId?.GetHashCode() ?? 0);
             hashCode = (hashCode * 397) ^ (Url?.GetHashCode() ?? 0);
             return hashCode;
diff --git a/Ical.Net/Collections/Proxies/GroupedValueListProxy.cs b/Ical.Net/Collections/Proxies/GroupedValueListProxy.cs
index ab5181450..7b0476428 100644
--- a/Ical.Net/Collections/Proxies/GroupedValueListProxy.cs
+++ b/Ical.Net/Collections/Proxies/GroupedValueListProxy.cs
@@ -64,7 +64,7 @@ private void IterateValues(Func<IValueObject<TOriginalValue>, int, int, bool> ac
         foreach (var obj in _realObject)
         {
             // Get the number of items of the target value i this object
-            var count = obj.Values?.OfType<TNewValue>().Count() ?? 0;
+            var count = obj.Values.OfType<TNewValue>().Count();
 
             // Perform some action on this item
             if (!action(obj, i, count))
diff --git a/Ical.Net/DataTypes/Attachment.cs b/Ical.Net/DataTypes/Attachment.cs
index 6cb6ba933..f7e212545 100644
--- a/Ical.Net/DataTypes/Attachment.cs
+++ b/Ical.Net/DataTypes/Attachment.cs
@@ -113,8 +113,8 @@ public override int GetHashCode()
         unchecked
         {
             var hashCode = Uri?.GetHashCode() ?? 0;
-            hashCode = (hashCode * 397) ^ (CollectionHelpers.GetHashCode(Data));
-            hashCode = (hashCode * 397) ^ (ValueEncoding?.GetHashCode() ?? 0);
+            hashCode = (hashCode * 397) ^ (Data != null ? CollectionHelpers.GetHashCode(Data) : 0);
+            hashCode = (hashCode * 397) ^ (ValueEncoding.GetHashCode());
             return hashCode;
         }
     }
diff --git a/Ical.Net/DataTypes/Occurrence.cs b/Ical.Net/DataTypes/Occurrence.cs
index e3f3b2ff0..d8c8ddc6a 100644
--- a/Ical.Net/DataTypes/Occurrence.cs
+++ b/Ical.Net/DataTypes/Occurrence.cs
@@ -41,7 +41,7 @@ public override int GetHashCode()
     {
         unchecked
         {
-            return ((Period?.GetHashCode() ?? 0) * 397) ^ (Source?.GetHashCode() ?? 0);
+            return ((Period.GetHashCode()) * 397) ^ (Source.GetHashCode());
         }
     }
 
diff --git a/Ical.Net/DataTypes/PeriodList.cs b/Ical.Net/DataTypes/PeriodList.cs
index b90bacc11..9d0ddbb79 100644
--- a/Ical.Net/DataTypes/PeriodList.cs
+++ b/Ical.Net/DataTypes/PeriodList.cs
@@ -125,7 +125,7 @@ public void Insert(int index, Period item)
     }
 
     /// <inheritdoc/>
-    public void RemoveAt(int index) => Periods?.RemoveAt(index);
+    public void RemoveAt(int index) => Periods.RemoveAt(index);
 
     /// <summary>
     /// Adds a <see cref="Period"/> to the list if it does not already exist.<br/>
@@ -159,7 +159,7 @@ public void Add(CalDateTime dt)
     public bool Contains(Period item) => Periods.Contains(item);
 
     /// <inheritdoc/>
-    public void CopyTo(Period[] array, int arrayIndex) => Periods?.CopyTo(array, arrayIndex);
+    public void CopyTo(Period[] array, int arrayIndex) => Periods.CopyTo(array, arrayIndex);
 
     /// <inheritdoc/>
     public IEnumerator<Period> GetEnumerator() => Periods.GetEnumerator();
diff --git a/Ical.Net/DataTypes/Trigger.cs b/Ical.Net/DataTypes/Trigger.cs
index becbe6aa1..1fc0248e5 100644
--- a/Ical.Net/DataTypes/Trigger.cs
+++ b/Ical.Net/DataTypes/Trigger.cs
@@ -119,7 +119,7 @@ public override int GetHashCode()
         {
             var hashCode = _mDateTime?.GetHashCode() ?? 0;
             hashCode = (hashCode * 397) ^ _mDuration.GetHashCode();
-            hashCode = (hashCode * 397) ^ _mRelated?.GetHashCode() ?? 0;
+            hashCode = (hashCode * 397) ^ _mRelated.GetHashCode();
             return hashCode;
         }
     }
diff --git a/Ical.Net/Evaluation/RecurrencePatternEvaluator.cs b/Ical.Net/Evaluation/RecurrencePatternEvaluator.cs
index 8b07df17f..a07ca11a8 100644
--- a/Ical.Net/Evaluation/RecurrencePatternEvaluator.cs
+++ b/Ical.Net/Evaluation/RecurrencePatternEvaluator.cs
@@ -100,10 +100,10 @@ private RecurrencePattern ProcessRecurrencePattern(CalDateTime referenceDate)
 
         // Pre-order those BY values that don't allow for negative values. Those with negative values can only
         // be ordered once the individual position is known.
-        if (r.BySecond?.Count > 0) r.BySecond = r.BySecond.OrderBy(x => x).ToList();
-        if (r.ByMinute?.Count > 0) r.ByMinute = r.ByMinute.OrderBy(x => x).ToList();
-        if (r.ByHour?.Count > 0) r.ByHour = r.ByHour.OrderBy(x => x).ToList();
-        if (r.ByMonth?.Count > 0) r.ByMonth = r.ByMonth.OrderBy(x => x).ToList();
+        if (r.BySecond.Count > 0) r.BySecond = r.BySecond.OrderBy(x => x).ToList();
+        if (r.ByMinute.Count > 0) r.ByMinute = r.ByMinute.OrderBy(x => x).ToList();
+        if (r.ByHour.Count > 0) r.ByHour = r.ByHour.OrderBy(x => x).ToList();
+        if (r.ByMonth.Count > 0) r.ByMonth = r.ByMonth.OrderBy(x => x).ToList();
 
         return r;
     }
diff --git a/Ical.Net/Serialization/ComponentSerializer.cs b/Ical.Net/Serialization/ComponentSerializer.cs
index d101c70ec..d606e8658 100644
--- a/Ical.Net/Serialization/ComponentSerializer.cs
+++ b/Ical.Net/Serialization/ComponentSerializer.cs
@@ -45,7 +45,7 @@ public ComponentSerializer(SerializationContext ctx) : base(ctx) { }
         foreach (var p in properties)
         {
             // Get a serializer for each property.
-            var serializer = sf?.Build(p.GetType(), SerializationContext) as IStringSerializer;
+            var serializer = sf.Build(p.GetType(), SerializationContext) as IStringSerializer;
             var val = serializer?.SerializeToString(p);
             if (val != null) sb.Append(val);
         }
diff --git a/Ical.Net/Serialization/DataTypes/DataTypeSerializer.cs b/Ical.Net/Serialization/DataTypes/DataTypeSerializer.cs
index 35830a1ed..85ef5cc09 100644
--- a/Ical.Net/Serialization/DataTypes/DataTypeSerializer.cs
+++ b/Ical.Net/Serialization/DataTypes/DataTypeSerializer.cs
@@ -23,7 +23,7 @@ protected DataTypeSerializer(SerializationContext ctx) : base(ctx) { }
             return null;
         }
 
-        if (SerializationContext?.Peek() is ICalendarObject associatedObject)
+        if (SerializationContext.Peek() is ICalendarObject associatedObject)
         {
             dt.AssociatedObject = associatedObject;
         }
diff --git a/Ical.Net/Serialization/DataTypes/DateTimeSerializer.cs b/Ical.Net/Serialization/DataTypes/DateTimeSerializer.cs
index dd82b6555..68b010bfa 100644
--- a/Ical.Net/Serialization/DataTypes/DateTimeSerializer.cs
+++ b/Ical.Net/Serialization/DataTypes/DateTimeSerializer.cs
@@ -68,7 +68,7 @@ public DateTimeSerializer(SerializationContext ctx) : base(ctx) { }
         var value = tr.ReadToEnd();
 
         // CalDateTime is defined as the Target type
-        var parent = SerializationContext?.Peek();
+        var parent = SerializationContext.Peek();
 
         // The associated object is an ICalendarObject of type CalendarProperty
         // that contains any timezone ("TZID" property) deserialized in a prior step
diff --git a/Ical.Net/Serialization/DataTypes/EncodableDataTypeSerializer.cs b/Ical.Net/Serialization/DataTypes/EncodableDataTypeSerializer.cs
index 5915e97a4..972b06497 100644
--- a/Ical.Net/Serialization/DataTypes/EncodableDataTypeSerializer.cs
+++ b/Ical.Net/Serialization/DataTypes/EncodableDataTypeSerializer.cs
@@ -28,9 +28,8 @@ protected EncodableDataTypeSerializer(SerializationContext ctx) : base(ctx) { }
 
         // Return the value in the current encoding
         var encodingStack = GetService<EncodingStack>();
-        return encodingStack?.Current == null
-            ? value
-            : Encode(dt, encodingStack.Current.GetBytes(value));
+
+        return Encode(dt, encodingStack.Current.GetBytes(value));
     }
 
     protected string? Encode(IEncodableDataType dt, byte[]? data)
@@ -44,11 +43,11 @@ protected EncodableDataTypeSerializer(SerializationContext ctx) : base(ctx) { }
         {
             // Default to the current encoding
             var encodingStack = GetService<EncodingStack>();
-            return encodingStack?.Current.GetString(data);
+            return encodingStack.Current.GetString(data);
         }
 
         var encodingProvider = GetService<IEncodingProvider>();
-        return encodingProvider?.Encode(dt.Encoding, data);
+        return encodingProvider.Encode(dt.Encoding, data);
     }
 
     protected string? Decode(IEncodableDataType dt, string value)
@@ -66,7 +65,7 @@ protected EncodableDataTypeSerializer(SerializationContext ctx) : base(ctx) { }
 
         // Default to the current encoding
         var encodingStack = GetService<EncodingStack>();
-        return encodingStack?.Current.GetString(data);
+        return encodingStack.Current.GetString(data);
     }
 
     protected byte[]? DecodeData(IEncodableDataType dt, string? value)
@@ -80,10 +79,10 @@ protected EncodableDataTypeSerializer(SerializationContext ctx) : base(ctx) { }
         {
             // Default to the current encoding
             var encodingStack = GetService<EncodingStack>();
-            return encodingStack?.Current.GetBytes(value);
+            return encodingStack.Current.GetBytes(value);
         }
 
         var encodingProvider = GetService<IEncodingProvider>();
-        return encodingProvider?.DecodeData(dt.Encoding, value);
+        return encodingProvider.DecodeData(dt.Encoding, value);
     }
 }
diff --git a/Ical.Net/Serialization/DataTypes/EnumSerializer.cs b/Ical.Net/Serialization/DataTypes/EnumSerializer.cs
index 5507adf6c..10d8b9183 100644
--- a/Ical.Net/Serialization/DataTypes/EnumSerializer.cs
+++ b/Ical.Net/Serialization/DataTypes/EnumSerializer.cs
@@ -30,7 +30,7 @@ public EnumSerializer(Type enumType, SerializationContext ctx) : base(ctx)
     {
         try
         {
-            if (SerializationContext?.Peek() is ICalendarObject calObject)
+            if (SerializationContext.Peek() is ICalendarObject calObject)
             {
                 // Encode the value as needed.
                 var dt = new EncodableDataType
@@ -53,7 +53,7 @@ public EnumSerializer(Type enumType, SerializationContext ctx) : base(ctx)
 
         try
         {
-            if (SerializationContext?.Peek() is ICalendarObject obj)
+            if (SerializationContext.Peek() is ICalendarObject obj)
             {
                 // Decode the value, if necessary!
                 var dt = new EncodableDataType
diff --git a/Ical.Net/Serialization/DataTypes/IntegerSerializer.cs b/Ical.Net/Serialization/DataTypes/IntegerSerializer.cs
index 0bf785757..84814a603 100644
--- a/Ical.Net/Serialization/DataTypes/IntegerSerializer.cs
+++ b/Ical.Net/Serialization/DataTypes/IntegerSerializer.cs
@@ -24,7 +24,7 @@ public IntegerSerializer(SerializationContext ctx) : base(ctx) { }
         {
             var i = Convert.ToInt32(obj);
 
-            if (SerializationContext?.Peek() is ICalendarObject calObject)
+            if (SerializationContext.Peek() is ICalendarObject calObject)
             {
                 // Encode the value as needed.
                 var dt = new EncodableDataType
@@ -47,7 +47,7 @@ public IntegerSerializer(SerializationContext ctx) : base(ctx) { }
 
         try
         {
-            if (SerializationContext?.Peek() is ICalendarObject obj)
+            if (SerializationContext.Peek() is ICalendarObject obj)
             {
                 // Decode the value, if necessary!
                 var dt = new EncodableDataType
diff --git a/Ical.Net/Serialization/DataTypes/PeriodSerializer.cs b/Ical.Net/Serialization/DataTypes/PeriodSerializer.cs
index b2f19dce4..351c99379 100644
--- a/Ical.Net/Serialization/DataTypes/PeriodSerializer.cs
+++ b/Ical.Net/Serialization/DataTypes/PeriodSerializer.cs
@@ -29,7 +29,7 @@ public PeriodSerializer(SerializationContext ctx) : base(ctx) { }
         }
 
         // Push the period onto the serialization context stack
-        SerializationContext?.Push(p);
+        SerializationContext.Push(p);
 
         try
         {
@@ -71,7 +71,7 @@ public PeriodSerializer(SerializationContext ctx) : base(ctx) { }
         finally
         {
             // Pop the period off the serialization context stack
-            SerializationContext?.Pop();
+            SerializationContext.Pop();
         }
     }
 
diff --git a/Ical.Net/Serialization/DataTypes/RequestStatusSerializer.cs b/Ical.Net/Serialization/DataTypes/RequestStatusSerializer.cs
index 067deca13..c40a31563 100644
--- a/Ical.Net/Serialization/DataTypes/RequestStatusSerializer.cs
+++ b/Ical.Net/Serialization/DataTypes/RequestStatusSerializer.cs
@@ -40,7 +40,7 @@ public RequestStatusSerializer(SerializationContext ctx) : base(ctx) { }
             try
             {
                 var factory = GetService<ISerializerFactory>();
-                var serializer = factory?.Build(typeof(StatusCode), SerializationContext) as IStringSerializer;
+                var serializer = factory.Build(typeof(StatusCode), SerializationContext) as IStringSerializer;
                 if (serializer == null)
                 {
                     return null;
@@ -60,7 +60,7 @@ public RequestStatusSerializer(SerializationContext ctx) : base(ctx) { }
             finally
             {
                 // Pop the object off the serialization stack
-                SerializationContext?.Pop();
+                SerializationContext.Pop();
             }
         }
         catch
@@ -128,7 +128,7 @@ public RequestStatusSerializer(SerializationContext ctx) : base(ctx) { }
         finally
         {
             // Pop the object off the serialization stack
-            SerializationContext?.Pop();
+            SerializationContext.Pop();
         }
         return null;
     }
diff --git a/Ical.Net/Serialization/DataTypes/StringSerializer.cs b/Ical.Net/Serialization/DataTypes/StringSerializer.cs
index d74b322d2..736d24112 100644
--- a/Ical.Net/Serialization/DataTypes/StringSerializer.cs
+++ b/Ical.Net/Serialization/DataTypes/StringSerializer.cs
@@ -81,7 +81,7 @@ public StringSerializer(SerializationContext ctx) : base(ctx) { }
             values.AddRange(from object child in enumerable select child.ToString());
         }
 
-        if (SerializationContext?.Peek() is ICalendarObject co)
+        if (SerializationContext.Peek() is ICalendarObject co)
         {
             // Encode the string as needed.
             var dt = new EncodableDataType
@@ -125,18 +125,15 @@ public StringSerializer(SerializationContext ctx) : base(ctx) { }
 
         // Ensure SerializationContext is not null before accessing Peek()
         var context = SerializationContext;
-        if (context?.Peek() is ICalendarProperty cp)
+        if (context.Peek() is ICalendarProperty cp)
         {
             var dataTypeMapper = GetService<DataTypeMapper>();
-            if (dataTypeMapper != null)
-            {
-                serializeAsList = dataTypeMapper.GetPropertyAllowsMultipleValues(cp);
-            }
+            serializeAsList = dataTypeMapper.GetPropertyAllowsMultipleValues(cp);
         }
 
         var dt = new EncodableDataType
         {
-            AssociatedObject = context?.Peek() as ICalendarObject
+            AssociatedObject = context.Peek() as ICalendarObject
         };
 
         var encodedValues = serializeAsList ? UnescapedCommas.Split(value) : new[] { value };
diff --git a/Ical.Net/Serialization/DataTypes/TriggerSerializer.cs b/Ical.Net/Serialization/DataTypes/TriggerSerializer.cs
index 39c292694..e536d23ee 100644
--- a/Ical.Net/Serialization/DataTypes/TriggerSerializer.cs
+++ b/Ical.Net/Serialization/DataTypes/TriggerSerializer.cs
@@ -28,7 +28,7 @@ public TriggerSerializer(SerializationContext ctx) : base(ctx) { }
             }
 
             // Push the trigger onto the serialization stack
-            SerializationContext?.Push(t);
+            SerializationContext.Push(t);
             try
             {
                 var factory = GetService<ISerializerFactory>();
@@ -52,7 +52,7 @@ public TriggerSerializer(SerializationContext ctx) : base(ctx) { }
             finally
             {
                 // Pop the trigger off the serialization stack
-                SerializationContext?.Pop();
+                SerializationContext.Pop();
             }
         }
         catch
@@ -73,7 +73,7 @@ public TriggerSerializer(SerializationContext ctx) : base(ctx) { }
         }
 
         // Push the trigger onto the serialization stack
-        SerializationContext?.Push(t);
+        SerializationContext.Push(t);
         try
         {
             // Decode the value as needed
@@ -82,7 +82,8 @@ public TriggerSerializer(SerializationContext ctx) : base(ctx) { }
             if (value == null) return null;
 
             // Set the trigger relation
-            if (t.Parameters.ContainsKey("RELATED") && t.Parameters.Get("RELATED").Equals("END"))
+            var relatedParameter = t.Parameters.Get("RELATED");
+            if (relatedParameter is not null && relatedParameter.Equals("END"))
             {
                 t.Related = TriggerRelation.End;
             }
@@ -113,7 +114,7 @@ public TriggerSerializer(SerializationContext ctx) : base(ctx) { }
         finally
         {
             // Pop the trigger off the serialization stack
-            SerializationContext?.Pop();
+            SerializationContext.Pop();
         }
     }
 }
diff --git a/Ical.Net/Serialization/DataTypes/UriSerializer.cs b/Ical.Net/Serialization/DataTypes/UriSerializer.cs
index 104b3fdcc..34dca5cf0 100644
--- a/Ical.Net/Serialization/DataTypes/UriSerializer.cs
+++ b/Ical.Net/Serialization/DataTypes/UriSerializer.cs
@@ -25,7 +25,7 @@ public UriSerializer(SerializationContext ctx) : base(ctx) { }
             return null;
         }
 
-        if (SerializationContext?.Peek() is ICalendarObject co)
+        if (SerializationContext.Peek() is ICalendarObject co)
         {
             var dt = new EncodableDataType
             {
@@ -45,7 +45,7 @@ public UriSerializer(SerializationContext ctx) : base(ctx) { }
 
         var value = tr.ReadToEnd();
 
-        if (SerializationContext?.Peek() is ICalendarObject co)
+        if (SerializationContext.Peek() is ICalendarObject co)
         {
             var dt = new EncodableDataType
             {
diff --git a/Ical.Net/Serialization/EncodingProvider.cs b/Ical.Net/Serialization/EncodingProvider.cs
index 67ab601a7..fb55c35c9 100644
--- a/Ical.Net/Serialization/EncodingProvider.cs
+++ b/Ical.Net/Serialization/EncodingProvider.cs
@@ -5,6 +5,7 @@
 
 #nullable enable
 using System;
+using System.Runtime.Serialization;
 using System.Text;
 
 namespace Ical.Net.Serialization;
@@ -19,7 +20,7 @@ internal class EncodingProvider : IEncodingProvider
     /// <summary>
     /// Represents a method that encodes a byte array into a string.
     /// </summary>
-    public delegate string? EncoderDelegate(byte[] data);
+    public delegate string EncoderDelegate(byte[] data);
 
     /// <summary>
     /// Represents a method that decodes a string into a byte array.
@@ -60,14 +61,14 @@ protected byte[] DecodeBase64(string value)
     /// Gets a decoder for the specified encoding.
     /// </summary>
     /// <param name="encoding"></param>
-    /// <returns></returns>
-    protected virtual DecoderDelegate? GetDecoderFor(string encoding)
+    /// <exception cref="SerializationException">Decoder not supported.</exception>
+    protected virtual DecoderDelegate GetDecoderFor(string encoding)
     {
         return encoding.ToUpper() switch
         {
             "8BIT" => Decode8Bit,
             "BASE64" => DecodeBase64,
-            _ => null,
+            _ => throw new SerializationException($"Encoding '{encoding}' is not supported.")
         };
     }
 
@@ -96,14 +97,14 @@ protected string EncodeBase64(byte[] data)
     /// Gets an encoder for the specified encoding.
     /// </summary>
     /// <param name="encoding"></param>
-    /// <returns></returns>
-    protected virtual EncoderDelegate? GetEncoderFor(string encoding)
+    /// <exception cref="SerializationException">Encoder not supported.</exception>
+    protected virtual EncoderDelegate GetEncoderFor(string encoding)
     {
         return encoding.ToUpper() switch
         {
             "8BIT" => Encode8Bit,
             "BASE64" => EncodeBase64,
-            _ => null
+            _ => throw new SerializationException($"Encoding '{encoding}' is not supported.")
         };
     }
 
@@ -113,10 +114,10 @@ protected string EncodeBase64(byte[] data)
     /// <param name="encoding"></param>
     /// <param name="data"></param>
     /// <returns>A string representation of <paramref name="data"/> using the specified <see paramref="encoding"/>, or <see langword="null"/> if encoding fails.</returns>
-    public string? Encode(string encoding, byte[] data)
+    public string Encode(string encoding, byte[] data)
     {
         var encoder = GetEncoderFor(encoding);
-        return encoder?.Invoke(data);
+        return encoder.Invoke(data);
     }
 
     /// <summary>
@@ -126,13 +127,13 @@ protected string EncodeBase64(byte[] data)
     /// <param name="value"></param>
     /// <returns>A string representation of <paramref name="value"/> using the specified <see paramref="encoding"/>.</returns>
     /// <exception cref="FormatException">Base64 string is invalid.</exception>
-    public string? DecodeString(string encoding, string value)
+    public string DecodeString(string encoding, string value)
     {
         var data = DecodeData(encoding, value);
 
         // Decode the string into the current encoding
-        var encodingStack = _mSerializationContext.GetService(typeof(EncodingStack)) as EncodingStack;
-        return data != null ? encodingStack?.Current.GetString(data) : null;
+        var encodingStack = (EncodingStack) _mSerializationContext.GetService(typeof(EncodingStack));
+        return encodingStack.Current.GetString(data);
     }
 
     /// <summary>
@@ -141,9 +142,9 @@ protected string EncodeBase64(byte[] data)
     /// <param name="encoding"></param>
     /// <param name="value"></param>
     /// <returns>A string representation of <paramref name="value"/> using the specified <see paramref="encoding"/>, or <see langword="null"/> when decoding fails.</returns>
-    public byte[]? DecodeData(string encoding, string value)
+    public byte[] DecodeData(string encoding, string value)
     {
         var decoder = GetDecoderFor(encoding);
-        return decoder?.Invoke(value);
+        return decoder.Invoke(value);
     }
 }
diff --git a/Ical.Net/Serialization/GenericListSerializer.cs b/Ical.Net/Serialization/GenericListSerializer.cs
index ae9899f82..1775294f8 100644
--- a/Ical.Net/Serialization/GenericListSerializer.cs
+++ b/Ical.Net/Serialization/GenericListSerializer.cs
@@ -32,7 +32,7 @@ public GenericListSerializer(Type objectType)
     private MethodInfo? _addMethodInfo;
     public override object? Deserialize(TextReader tr)
     {
-        var p = SerializationContext?.Peek() as ICalendarProperty;
+        var p = SerializationContext.Peek() as ICalendarProperty;
         if (p == null)
         {
             return null;
@@ -47,7 +47,7 @@ public GenericListSerializer(Type objectType)
 
         // Get a serializer for the inner type
         var sf = GetService<ISerializerFactory>();
-        var stringSerializer = sf?.Build(_innerType, SerializationContext) as IStringSerializer;
+        var stringSerializer = sf.Build(_innerType, SerializationContext) as IStringSerializer;
         if (stringSerializer == null)
         {
             return null;
diff --git a/Ical.Net/Serialization/IEncodingProvider.cs b/Ical.Net/Serialization/IEncodingProvider.cs
index 2e353d080..6d48e950f 100644
--- a/Ical.Net/Serialization/IEncodingProvider.cs
+++ b/Ical.Net/Serialization/IEncodingProvider.cs
@@ -8,7 +8,7 @@ namespace Ical.Net.Serialization;
 
 internal interface IEncodingProvider
 {
-    string Encode(string encoding, byte[] data);
-    string DecodeString(string encoding, string value);
-    byte[] DecodeData(string encoding, string value);
+    string? Encode(string encoding, byte[] data);
+    string? DecodeString(string encoding, string value);
+    byte[]? DecodeData(string encoding, string value);
 }
diff --git a/Ical.Net/Serialization/ISerializer.cs b/Ical.Net/Serialization/ISerializer.cs
index f72c4e7bd..47a2d38f8 100644
--- a/Ical.Net/Serialization/ISerializer.cs
+++ b/Ical.Net/Serialization/ISerializer.cs
@@ -12,7 +12,7 @@ namespace Ical.Net.Serialization;
 
 public interface ISerializer : IServiceProvider
 {
-    SerializationContext? SerializationContext { get; set; }
+    SerializationContext SerializationContext { get; set; }
 
     Type TargetType { get; }
     void Serialize(object obj, Stream stream, Encoding encoding);
diff --git a/Ical.Net/Serialization/PropertySerializer.cs b/Ical.Net/Serialization/PropertySerializer.cs
index 4edf76b3e..de4e5fada 100644
--- a/Ical.Net/Serialization/PropertySerializer.cs
+++ b/Ical.Net/Serialization/PropertySerializer.cs
@@ -31,12 +31,11 @@ public PropertySerializer(SerializationContext ctx) : base(ctx) { }
         }
 
         // Push this object on the serialization context.
-        SerializationContext?.Push(prop);
+        SerializationContext.Push(prop);
 
         // Get a serializer factory that we can use to serialize
         // the property and parameter values
         var sf = GetService<ISerializerFactory>();
-        if (sf == null) return null;
 
         var result = new StringBuilder();
         foreach (var v in prop.Values.Where(value => value != null))
@@ -45,7 +44,7 @@ public PropertySerializer(SerializationContext ctx) : base(ctx) { }
         }
 
         // Pop the object off the serialization context.
-        SerializationContext?.Pop();
+        SerializationContext.Pop();
         return result.ToString();
     }
 
diff --git a/Ical.Net/Serialization/SerializerBase.cs b/Ical.Net/Serialization/SerializerBase.cs
index d238b7bea..dd94c25a6 100644
--- a/Ical.Net/Serialization/SerializerBase.cs
+++ b/Ical.Net/Serialization/SerializerBase.cs
@@ -12,7 +12,7 @@ namespace Ical.Net.Serialization;
 
 public abstract class SerializerBase : IStringSerializer
 {
-    private SerializationContext? _mSerializationContext;
+    private SerializationContext _mSerializationContext;
 
     protected SerializerBase()
     {
@@ -24,7 +24,7 @@ protected SerializerBase(SerializationContext ctx)
         _mSerializationContext = ctx;
     }
 
-    public virtual SerializationContext? SerializationContext // NOSONAR: auto-property
+    public virtual SerializationContext SerializationContext // NOSONAR: auto-property
     {
         get => _mSerializationContext;
         set => _mSerializationContext = value;
@@ -38,9 +38,9 @@ protected SerializerBase(SerializationContext ctx)
     {
         using var sr = new StreamReader(stream, encoding);
         var encodingStack = GetService<EncodingStack>();
-        encodingStack?.Push(encoding);
+        encodingStack.Push(encoding);
         var obj = Deserialize(sr);
-        encodingStack?.Pop();
+        encodingStack.Pop();
         return obj;
     }
 
@@ -54,40 +54,40 @@ public void Serialize(object obj, Stream stream, Encoding encoding)
         using var sw = new StreamWriter(stream, encoding, defaultBuffer, leaveOpen: true);
 
         // Push the current object onto the serialization stack
-        SerializationContext?.Push(obj);
+        SerializationContext.Push(obj);
 
         // Push the current encoding on the stack
         var encodingStack = GetService<EncodingStack>();
-        encodingStack?.Push(encoding);
+        encodingStack.Push(encoding);
 
         sw.Write(SerializeToString(obj));
 
         // Pop the current encoding off the serialization stack
-        encodingStack?.Pop();
+        encodingStack.Pop();
 
         // Pop the current object off the serialization stack
-        SerializationContext?.Pop();
+        SerializationContext.Pop();
     }
 
-    public virtual object? GetService(Type serviceType) => SerializationContext?.GetService(serviceType);
+    public virtual object GetService(Type serviceType) => SerializationContext.GetService(serviceType);
 
-    public virtual object? GetService(string name) => SerializationContext?.GetService(name);
+    public virtual object GetService(string name) => SerializationContext.GetService(name);
 
-    public virtual T? GetService<T>()
-        => SerializationContext != null ? SerializationContext.GetService<T>() : default;
+    public virtual T GetService<T>()
+        => SerializationContext.GetService<T>();
 
-    public virtual T? GetService<T>(string name) =>
-        SerializationContext != null ? SerializationContext.GetService<T>(name) : default;
+    public virtual T GetService<T>(string name) =>
+        SerializationContext.GetService<T>(name);
 
     public void SetService(string name, object obj)
-        => SerializationContext?.SetService(name, obj);
+        => SerializationContext.SetService(name, obj);
 
     public void SetService(object obj)
-        => SerializationContext?.SetService(obj);
+        => SerializationContext.SetService(obj);
 
     public void RemoveService(Type type)
-        => SerializationContext?.RemoveService(type);
+        => SerializationContext.RemoveService(type);
 
     public void RemoveService(string name)
-        => SerializationContext?.RemoveService(name);
+        => SerializationContext.RemoveService(name);
 }
diff --git a/Ical.Net/Serialization/SimpleDeserializer.cs b/Ical.Net/Serialization/SimpleDeserializer.cs
index 17e4683ff..5b36147ae 100644
--- a/Ical.Net/Serialization/SimpleDeserializer.cs
+++ b/Ical.Net/Serialization/SimpleDeserializer.cs
@@ -77,15 +77,19 @@ private static string BuildContentLineRegex()
     public IEnumerable<ICalendarComponent> Deserialize(TextReader reader)
     {
         var context = new SerializationContext();
-        var stack = new Stack<ICalendarComponent>();
+        var stack = new Stack<ICalendarComponent?>();
         var current = default(ICalendarComponent);
         foreach (var contentLineString in GetContentLines(reader))
         {
             var contentLine = ParseContentLine(context, contentLineString);
             if (string.Equals(contentLine.Name, "BEGIN", StringComparison.OrdinalIgnoreCase))
             {
-                stack.Push(current!); // Must push to stack!
-                current = _componentFactory.Build((string) contentLine.Value);
+                stack.Push(current); // Must push to stack!
+                if (contentLine.Value is not string value)
+                {
+                    throw new SerializationException("Content line value is null or not a string.");
+                }
+                current = _componentFactory.Build(value);
                 SerializationUtil.OnDeserializing(current);
             }
             else
@@ -96,10 +100,15 @@ public IEnumerable<ICalendarComponent> Deserialize(TextReader reader)
                 }
                 if (string.Equals(contentLine.Name, "END", StringComparison.OrdinalIgnoreCase))
                 {
-                    if (!string.Equals((string) contentLine.Value, current.Name, StringComparison.OrdinalIgnoreCase))
+                    if (contentLine.Value is not string value)
                     {
-                        throw new SerializationException($"Expected 'END:{current.Name}', found 'END:{contentLine.Value}'");
+                        throw new SerializationException("Content line value is null or not a string.");
                     }
+                    if (!string.Equals(value, current.Name, StringComparison.OrdinalIgnoreCase))
+                    {
+                        throw new SerializationException($"Expected 'END:{current.Name}', found 'END:{value}'");
+                    }
+
                     SerializationUtil.OnDeserialized(current);
                     var finished = current;
                     current = stack.Pop();
@@ -165,7 +174,7 @@ private static void SetPropertyParameters(CalendarProperty property, CaptureColl
     private void SetPropertyValue(SerializationContext context, CalendarProperty property, string value)
     {
         var type = _dataTypeMapper.GetPropertyMapping(property) ?? typeof(string);
-        var serializer = (SerializerBase?) _serializerFactory.Build(type, context);
+        var serializer = _serializerFactory.Build(type, context) as SerializerBase;
         using var valueReader = new StringReader(value);
 
         var propertyValue = serializer?.Deserialize(valueReader);
diff --git a/Ical.Net/ServiceProvider.cs b/Ical.Net/ServiceProvider.cs
index 7a7542ecf..1cd35eee2 100644
--- a/Ical.Net/ServiceProvider.cs
+++ b/Ical.Net/ServiceProvider.cs
@@ -15,37 +15,25 @@ public class ServiceProvider
     private readonly IDictionary<Type, object> _mTypedServices = new Dictionary<Type, object>();
     private readonly IDictionary<string, object> _mNamedServices = new Dictionary<string, object>();
 
-    public virtual object? GetService(Type serviceType)
+    public virtual object GetService(Type serviceType)
     {
-        _mTypedServices.TryGetValue(serviceType, out var service);
+        if (!_mTypedServices.TryGetValue(serviceType, out var service))
+            throw new ArgumentException($"Service of type {serviceType.FullName} not found.", nameof(serviceType));
+
         return service;
     }
 
-    public virtual object? GetService(string name)
+    public virtual object GetService(string name)
     {
-        _mNamedServices.TryGetValue(name, out var service);
+        if (!_mNamedServices.TryGetValue(name, out var service))
+            throw new ArgumentException($"Service with name {name} not found.", nameof(name));
+
         return service;
     }
 
-    public virtual T? GetService<T>()
-    {
-        var service = GetService(typeof(T));
-        if (service is T svc)
-        {
-            return svc;
-        }
-        return default(T);
-    }
+    public virtual T GetService<T>() => (T) GetService(typeof(T));
 
-    public virtual T? GetService<T>(string name)
-    {
-        var service = GetService(name);
-        if (service is T svc)
-        {
-            return svc;
-        }
-        return default(T);
-    }
+    public virtual T GetService<T>(string name) => (T) GetService(name);
 
     public virtual void SetService(string name, object obj)
     {