diff --git a/src/NHapi.Base/EventMapper.cs b/src/NHapi.Base/EventMapper.cs
index cabab954e..d69d89a0d 100644
--- a/src/NHapi.Base/EventMapper.cs
+++ b/src/NHapi.Base/EventMapper.cs
@@ -10,7 +10,7 @@ internal class EventMapper
     {
         private static readonly EventMapper InstanceValue = new EventMapper();
 
-        private Hashtable map = new Hashtable();
+        private readonly Hashtable map = new Hashtable();
 
         static EventMapper()
         {
diff --git a/src/NHapi.Base/Log/HapiLogImpl.cs b/src/NHapi.Base/Log/HapiLogImpl.cs
index 14b82155b..c94a65a36 100644
--- a/src/NHapi.Base/Log/HapiLogImpl.cs
+++ b/src/NHapi.Base/Log/HapiLogImpl.cs
@@ -20,7 +20,7 @@ namespace NHapi.Base.Log
     /// </version>
     public class HapiLogImpl : IHapiLog
     {
-        private ILog innerLog;
+        private readonly ILog innerLog;
 
         internal HapiLogImpl(ILog log)
         {
diff --git a/src/NHapi.Base/Model/AbstractGroup.cs b/src/NHapi.Base/Model/AbstractGroup.cs
index 0e3ac285f..719335acf 100644
--- a/src/NHapi.Base/Model/AbstractGroup.cs
+++ b/src/NHapi.Base/Model/AbstractGroup.cs
@@ -44,8 +44,8 @@ public abstract class AbstractGroup : IGroup
     {
         private static readonly IHapiLog Log;
 
+        private readonly IModelClassFactory myFactory;
         private List<AbstractGroupItem> items;
-        private IModelClassFactory myFactory;
 
         static AbstractGroup()
         {
diff --git a/src/NHapi.Base/Model/AbstractSegmentItem.cs b/src/NHapi.Base/Model/AbstractSegmentItem.cs
index fe55a114c..3f7654981 100644
--- a/src/NHapi.Base/Model/AbstractSegmentItem.cs
+++ b/src/NHapi.Base/Model/AbstractSegmentItem.cs
@@ -5,7 +5,7 @@ namespace NHapi.Base.Model
 
     internal class AbstractSegmentItem
     {
-        private List<object> args = new List<object>();
+        private readonly List<object> args = new List<object>();
         private int maxReps = -1;
 
         /// <summary>
diff --git a/src/NHapi.Base/Model/ExtraComponents.cs b/src/NHapi.Base/Model/ExtraComponents.cs
index c547efd24..b940c87e9 100644
--- a/src/NHapi.Base/Model/ExtraComponents.cs
+++ b/src/NHapi.Base/Model/ExtraComponents.cs
@@ -31,8 +31,8 @@ namespace NHapi.Base.Model
     /// <author>Bryan Tripp.</author>
     public class ExtraComponents
     {
-        private ArrayList comps;
-        private IMessage message;
+        private readonly ArrayList comps;
+        private readonly IMessage message;
 
         /// <summary>
         /// Creates a new instance of ExtraComponents.
diff --git a/src/NHapi.Base/Model/GenericComposite.cs b/src/NHapi.Base/Model/GenericComposite.cs
index 8f246189a..d5e4b2e49 100644
--- a/src/NHapi.Base/Model/GenericComposite.cs
+++ b/src/NHapi.Base/Model/GenericComposite.cs
@@ -11,7 +11,7 @@ namespace NHapi.Base.Model
     /// <author>Bryan Tripp.</author>
     public class GenericComposite : AbstractType, IComposite
     {
-        private ArrayList components;
+        private readonly ArrayList components;
 
         /// <summary>
         /// Creates a new instance of GenericComposite.
diff --git a/src/NHapi.Base/Model/GenericGroup.cs b/src/NHapi.Base/Model/GenericGroup.cs
index 03705ddd5..3ef464114 100644
--- a/src/NHapi.Base/Model/GenericGroup.cs
+++ b/src/NHapi.Base/Model/GenericGroup.cs
@@ -11,7 +11,7 @@ namespace NHapi.Base.Model
     /// <author>Bryan Tripp.</author>
     public class GenericGroup : AbstractGroup
     {
-        private string name;
+        private readonly string name;
 
         /// <summary>Creates a new instance of GenericGroup. </summary>
         public GenericGroup(IGroup parent, string name, IModelClassFactory factory)
diff --git a/src/NHapi.Base/Parser/EncodingCharacters.cs b/src/NHapi.Base/Parser/EncodingCharacters.cs
index 49eb2c161..9ca7cec7d 100644
--- a/src/NHapi.Base/Parser/EncodingCharacters.cs
+++ b/src/NHapi.Base/Parser/EncodingCharacters.cs
@@ -209,9 +209,9 @@ public virtual object Clone()
             return new EncodingCharacters(this);
         }
 
-        public override bool Equals(object o)
+        public override bool Equals(object obj)
         {
-            if (o is EncodingCharacters other)
+            if (obj is EncodingCharacters other)
             {
                 return FieldSeparator == other.FieldSeparator &&
                        ComponentSeparator == other.ComponentSeparator &&
diff --git a/src/NHapi.Base/Parser/MessageIterator.cs b/src/NHapi.Base/Parser/MessageIterator.cs
index 5a009f56b..a1b01c4c6 100644
--- a/src/NHapi.Base/Parser/MessageIterator.cs
+++ b/src/NHapi.Base/Parser/MessageIterator.cs
@@ -422,14 +422,14 @@ public int Rep
             /// <summary>
             /// Override equals.
             /// </summary>
-            /// <param name="o"></param>
+            /// <param name="obj"></param>
             /// <returns></returns>
-            public override bool Equals(object o)
+            public override bool Equals(object obj)
             {
                 var equals = false;
-                if (o != null && o is Index)
+                if (obj != null && obj is Index)
                 {
-                    var i = (Index)o;
+                    var i = (Index)obj;
                     if (i.Rep == Rep && i.Name.Equals(Name))
                     {
                         equals = true;
diff --git a/src/NHapi.Base/Parser/XMLParser.cs b/src/NHapi.Base/Parser/XMLParser.cs
index 6e4ba568a..4aec12f12 100644
--- a/src/NHapi.Base/Parser/XMLParser.cs
+++ b/src/NHapi.Base/Parser/XMLParser.cs
@@ -50,7 +50,7 @@ public abstract class XMLParser : ParserBase
     {
         private static readonly IHapiLog Log;
 
-        private XmlDocument parser;
+        private readonly XmlDocument parser;
 
         /// <summary>
         /// The nodes whose names match these strings will be kept as original,
diff --git a/src/NHapi.Base/Util/FilterIterator.cs b/src/NHapi.Base/Util/FilterIterator.cs
index 16f95b26d..99c529ccb 100644
--- a/src/NHapi.Base/Util/FilterIterator.cs
+++ b/src/NHapi.Base/Util/FilterIterator.cs
@@ -47,8 +47,8 @@ namespace NHapi.Base.Util
     /// </summary>
     public class FilterIterator : IEnumerator
     {
-        private IPredicate predicate;
-        private IEnumerator iter;
+        private readonly IPredicate predicate;
+        private readonly IEnumerator iter;
         private object nextObject;
         private bool nextObjectSet = false;
 
diff --git a/src/NHapi.Base/Util/MessageIterator.cs b/src/NHapi.Base/Util/MessageIterator.cs
index f7a8c11af..6150ff56c 100644
--- a/src/NHapi.Base/Util/MessageIterator.cs
+++ b/src/NHapi.Base/Util/MessageIterator.cs
@@ -26,10 +26,10 @@ public class MessageIterator : IEnumerator
     {
         private static readonly IHapiLog Log;
 
+        private readonly bool handleUnexpectedSegments;
         private IStructure currentStructure;
         private string direction;
         private Position nextRenamedField;
-        private bool handleUnexpectedSegments;
 
         static MessageIterator()
         {
@@ -662,14 +662,14 @@ public Index Index
             /// <summary>
             /// Override equals operator.
             /// </summary>
-            /// <param name="o">Object o.</param>
+            /// <param name="obj">Object obj.</param>
             /// <returns>true if objects are equal.</returns>
-            public override bool Equals(object o)
+            public override bool Equals(object obj)
             {
                 var equals = false;
-                if (o != null && o is Position)
+                if (obj != null && obj is Position)
                 {
-                    var p = (Position)o;
+                    var p = (Position)obj;
                     if (p.Parent.Equals(Parent) && p.Index.Equals(Index))
                     {
                         equals = true;
diff --git a/src/NHapi.Base/Util/MessageNavigator.cs b/src/NHapi.Base/Util/MessageNavigator.cs
index 9463e5422..3231a34ee 100644
--- a/src/NHapi.Base/Util/MessageNavigator.cs
+++ b/src/NHapi.Base/Util/MessageNavigator.cs
@@ -164,7 +164,7 @@ public virtual bool drillUp()
         public virtual bool DrillUp()
         {
             // pop the top group and resume search there
-            if (!(ancestors.Count == 0))
+            if (ancestors.Count != 0)
             {
                 var gc = (GroupContext)SupportClass.StackSupport.Pop(ancestors);
                 CurrentGroup = gc.Group;
@@ -375,12 +375,12 @@ private void DrillHere(IStructure destination)
             }
 
             Reset();
-            while (!(pathStack.Count == 0))
+            while (pathStack.Count != 0)
             {
                 var parent = (IGroup)SupportClass.StackSupport.Pop(pathStack);
                 var index = (MessageIterator.Index)SupportClass.StackSupport.Pop(indexStack);
                 var child = Search(parent.Names, index.Name);
-                if (!(pathStack.Count == 0))
+                if (pathStack.Count != 0)
                 {
                     DrillDown(child, 0);
                 }
diff --git a/src/NHapi.Base/Validation/MessageValidator.cs b/src/NHapi.Base/Validation/MessageValidator.cs
index 5fef25f62..d05a13b86 100644
--- a/src/NHapi.Base/Validation/MessageValidator.cs
+++ b/src/NHapi.Base/Validation/MessageValidator.cs
@@ -42,8 +42,8 @@ public class MessageValidator
     {
         private static readonly IHapiLog OurLog;
 
-        private IValidationContext myContext;
-        private bool failOnError;
+        private readonly IValidationContext myContext;
+        private readonly bool failOnError;
 
         static MessageValidator()
         {