diff --git a/examples/Console/InstrumentationWithActivitySource.cs b/examples/Console/InstrumentationWithActivitySource.cs
index 0e2b320e25e..ee7927f8c0d 100644
--- a/examples/Console/InstrumentationWithActivitySource.cs
+++ b/examples/Console/InstrumentationWithActivitySource.cs
@@ -30,8 +30,8 @@ namespace Examples.Console
     internal class InstrumentationWithActivitySource : IDisposable
     {
         private const string RequestPath = "/api/request";
-        private SampleServer server = new SampleServer();
-        private SampleClient client = new SampleClient();
+        private readonly SampleServer server = new SampleServer();
+        private readonly SampleClient client = new SampleClient();
 
         public void Start(ushort port = 19999)
         {
@@ -48,7 +48,7 @@ public void Dispose()
 
         private class SampleServer : IDisposable
         {
-            private HttpListener listener = new HttpListener();
+            private readonly HttpListener listener = new HttpListener();
 
             public void Start(string url)
             {
diff --git a/src/OpenTelemetry.Exporter.ZPages/Implementation/ZPagesActivityTracker.cs b/src/OpenTelemetry.Exporter.ZPages/Implementation/ZPagesActivityTracker.cs
index b7011c74fbb..b09279f8834 100644
--- a/src/OpenTelemetry.Exporter.ZPages/Implementation/ZPagesActivityTracker.cs
+++ b/src/OpenTelemetry.Exporter.ZPages/Implementation/ZPagesActivityTracker.cs
@@ -26,7 +26,7 @@ namespace OpenTelemetry.Exporter.ZPages.Implementation
     /// </summary>
     internal static class ZPagesActivityTracker
     {
-        private static long startTime;
+        private static readonly long StartTime;
 
         /// <summary>
         /// Initializes static members of the <see cref="ZPagesActivityTracker"/> class.
@@ -41,7 +41,7 @@ static ZPagesActivityTracker()
             TotalEndedCount = new Dictionary<string, long>();
             TotalErrorCount = new Dictionary<string, long>();
             TotalLatency = new Dictionary<string, long>();
-            startTime = DateTimeOffset.Now.ToUnixTimeMilliseconds();
+            StartTime = DateTimeOffset.Now.ToUnixTimeMilliseconds();
         }
 
         /// <summary>
@@ -103,7 +103,7 @@ public static void PurgeCurrentMinuteData(object source, ElapsedEventArgs e)
             CurrentMinuteList.Clear();
 
             // Remove the stale activity information which is at the end of the list
-            if (DateTimeOffset.Now.ToUnixTimeMilliseconds() - startTime >= RetentionTime)
+            if (DateTimeOffset.Now.ToUnixTimeMilliseconds() - StartTime >= RetentionTime)
             {
                 ZQueue.RemoveLast();
             }
diff --git a/src/OpenTelemetry/CompositeProcessor.cs b/src/OpenTelemetry/CompositeProcessor.cs
index 2b504e6432a..cf2a2861ef6 100644
--- a/src/OpenTelemetry/CompositeProcessor.cs
+++ b/src/OpenTelemetry/CompositeProcessor.cs
@@ -24,7 +24,7 @@ namespace OpenTelemetry
 {
     public class CompositeProcessor<T> : BaseProcessor<T>
     {
-        private DoublyLinkedListNode head;
+        private readonly DoublyLinkedListNode head;
         private DoublyLinkedListNode tail;
         private bool disposed;
 
diff --git a/src/OpenTelemetry/DiagnosticSourceInstrumentation/DiagnosticSourceSubscriber.cs b/src/OpenTelemetry/DiagnosticSourceInstrumentation/DiagnosticSourceSubscriber.cs
index 6fc3fb28553..7af54876057 100644
--- a/src/OpenTelemetry/DiagnosticSourceInstrumentation/DiagnosticSourceSubscriber.cs
+++ b/src/OpenTelemetry/DiagnosticSourceInstrumentation/DiagnosticSourceSubscriber.cs
@@ -22,12 +22,12 @@ namespace OpenTelemetry.Instrumentation
 {
     internal class DiagnosticSourceSubscriber : IDisposable, IObserver<DiagnosticListener>
     {
+        private readonly List<IDisposable> listenerSubscriptions;
         private readonly Func<string, ListenerHandler> handlerFactory;
         private readonly Func<DiagnosticListener, bool> diagnosticSourceFilter;
         private readonly Func<string, object, object, bool> isEnabledFilter;
         private long disposed;
         private IDisposable allSourcesSubscription;
-        private List<IDisposable> listenerSubscriptions;
 
         public DiagnosticSourceSubscriber(
             ListenerHandler handler,
diff --git a/test/OpenTelemetry.Tests/Instrumentation/DiagnosticSourceListenerTest.cs b/test/OpenTelemetry.Tests/Instrumentation/DiagnosticSourceListenerTest.cs
index 9878cb5ae3b..7e9b6fc2de7 100644
--- a/test/OpenTelemetry.Tests/Instrumentation/DiagnosticSourceListenerTest.cs
+++ b/test/OpenTelemetry.Tests/Instrumentation/DiagnosticSourceListenerTest.cs
@@ -21,9 +21,9 @@ namespace OpenTelemetry.Instrumentation.Tests
     public class DiagnosticSourceListenerTest
     {
         private const string TestSourceName = "TestSourceName";
-        private DiagnosticSource diagnosticSource;
-        private TestListenerHandler testListenerHandler;
-        private DiagnosticSourceSubscriber testDiagnosticSourceSubscriber;
+        private readonly DiagnosticSource diagnosticSource;
+        private readonly TestListenerHandler testListenerHandler;
+        private readonly DiagnosticSourceSubscriber testDiagnosticSourceSubscriber;
 
         public DiagnosticSourceListenerTest()
         {