diff --git a/dotnet/src/webdriver/Remote/DriverServiceCommandExecutor.cs b/dotnet/src/webdriver/Remote/DriverServiceCommandExecutor.cs
index 2a374d5f5eb14..b9bb4efcf0084 100644
--- a/dotnet/src/webdriver/Remote/DriverServiceCommandExecutor.cs
+++ b/dotnet/src/webdriver/Remote/DriverServiceCommandExecutor.cs
@@ -20,6 +20,8 @@
 using System;
 using System.Threading.Tasks;
 
+#nullable enable
+
 namespace OpenQA.Selenium.Remote
 {
     /// <summary>
@@ -27,8 +29,7 @@ namespace OpenQA.Selenium.Remote
     /// </summary>
     public class DriverServiceCommandExecutor : ICommandExecutor
     {
-        private DriverService service;
-        private HttpCommandExecutor internalExecutor;
+        private readonly DriverService service;
         private bool isDisposed;
 
         /// <summary>
@@ -36,6 +37,7 @@ public class DriverServiceCommandExecutor : ICommandExecutor
         /// </summary>
         /// <param name="driverService">The <see cref="DriverService"/> that drives the browser.</param>
         /// <param name="commandTimeout">The maximum amount of time to wait for each command.</param>
+        /// <exception cref="ArgumentNullException">If <paramref name="driverService"/> is <see langword="null"/>.</exception>
         public DriverServiceCommandExecutor(DriverService driverService, TimeSpan commandTimeout)
             : this(driverService, commandTimeout, true)
         {
@@ -48,10 +50,11 @@ public DriverServiceCommandExecutor(DriverService driverService, TimeSpan comman
         /// <param name="commandTimeout">The maximum amount of time to wait for each command.</param>
         /// <param name="enableKeepAlive"><see langword="true"/> if the KeepAlive header should be sent
         /// with HTTP requests; otherwise, <see langword="false"/>.</param>
+        /// <exception cref="ArgumentNullException">If <paramref name="driverService"/> is <see langword="null"/>.</exception>
         public DriverServiceCommandExecutor(DriverService driverService, TimeSpan commandTimeout, bool enableKeepAlive)
         {
-            this.service = driverService;
-            this.internalExecutor = new HttpCommandExecutor(driverService.ServiceUrl, commandTimeout, enableKeepAlive);
+            this.service = driverService ?? throw new ArgumentNullException(nameof(driverService));
+            this.HttpExecutor = new HttpCommandExecutor(driverService.ServiceUrl, commandTimeout, enableKeepAlive);
         }
 
         /// <summary>
@@ -60,10 +63,11 @@ public DriverServiceCommandExecutor(DriverService driverService, TimeSpan comman
         /// <param name="service">The <see cref="DriverService"/> that drives the browser.</param>
         /// <param name="commandExecutor">The <see cref="HttpCommandExecutor"/> object used to execute commands,
         /// communicating with the service via HTTP.</param>
+        /// <exception cref="ArgumentNullException">If <paramref name="service"/> or <paramref name="commandExecutor"/> are <see langword="null"/>.</exception>
         public DriverServiceCommandExecutor(DriverService service, HttpCommandExecutor commandExecutor)
         {
-            this.service = service;
-            this.internalExecutor = commandExecutor;
+            this.service = service ?? throw new ArgumentNullException(nameof(service));
+            this.HttpExecutor = commandExecutor ?? throw new ArgumentNullException(nameof(commandExecutor));
         }
 
         /// <summary>
@@ -71,22 +75,19 @@ public DriverServiceCommandExecutor(DriverService service, HttpCommandExecutor c
         /// </summary>
         //public CommandInfoRepository CommandInfoRepository
         //{
-        //    get { return this.internalExecutor.CommandInfoRepository; }
+        //    get { return this.HttpExecutor.CommandInfoRepository; }
         //}
 
         public bool TryAddCommand(string commandName, CommandInfo info)
         {
-            return this.internalExecutor.TryAddCommand(commandName, info);
+            return this.HttpExecutor.TryAddCommand(commandName, info);
         }
 
         /// <summary>
         /// Gets the <see cref="HttpCommandExecutor"/> that sends commands to the remote
         /// end WebDriver implementation.
         /// </summary>
-        public HttpCommandExecutor HttpExecutor
-        {
-            get { return this.internalExecutor; }
-        }
+        public HttpCommandExecutor HttpExecutor { get; }
 
         /// <summary>
         /// Executes a command
@@ -110,7 +111,7 @@ public async Task<Response> ExecuteAsync(Command commandToExecute)
                 throw new ArgumentNullException(nameof(commandToExecute), "Command to execute cannot be null");
             }
 
-            Response toReturn = null;
+            Response toReturn;
             if (commandToExecute.Name == DriverCommand.NewSession)
             {
                 this.service.Start();
@@ -120,7 +121,7 @@ public async Task<Response> ExecuteAsync(Command commandToExecute)
             // command, so that we can get the finally block.
             try
             {
-                toReturn = await this.internalExecutor.ExecuteAsync(commandToExecute).ConfigureAwait(false);
+                toReturn = await this.HttpExecutor.ExecuteAsync(commandToExecute).ConfigureAwait(false);
             }
             finally
             {
@@ -139,6 +140,7 @@ public async Task<Response> ExecuteAsync(Command commandToExecute)
         public void Dispose()
         {
             this.Dispose(true);
+            GC.SuppressFinalize(this);
         }
 
         /// <summary>
@@ -153,7 +155,7 @@ protected virtual void Dispose(bool disposing)
             {
                 if (disposing)
                 {
-                    this.internalExecutor.Dispose();
+                    this.HttpExecutor.Dispose();
                     this.service.Dispose();
                 }
 
diff --git a/dotnet/src/webdriver/Remote/ICommandServer.cs b/dotnet/src/webdriver/Remote/ICommandServer.cs
index 395616482f7d5..f70d536dfd042 100644
--- a/dotnet/src/webdriver/Remote/ICommandServer.cs
+++ b/dotnet/src/webdriver/Remote/ICommandServer.cs
@@ -19,6 +19,8 @@
 
 using System;
 
+#nullable enable
+
 namespace OpenQA.Selenium.Remote
 {
     /// <summary>