diff --git a/dotnet/src/webdriver/INavigation.cs b/dotnet/src/webdriver/INavigation.cs
index a7cb84db9544f..5fd4e19e1cd58 100644
--- a/dotnet/src/webdriver/INavigation.cs
+++ b/dotnet/src/webdriver/INavigation.cs
@@ -66,7 +66,7 @@ public interface INavigation
         /// should the underlying page change while your test is executing the results of
         /// future calls against this interface will be against the freshly loaded page.
         /// </remarks>
-        /// <exception cref="ArgumentNullException">If <paramref name="url"/> is null.</exception>
+        /// <exception cref="ArgumentNullException">If <paramref name="url"/> is <see langword="null"/>.</exception>
         void GoToUrl(string url);
 
         /// <summary>
@@ -74,7 +74,7 @@ public interface INavigation
         /// </summary>
         /// <param name="url">String of where you want the browser to go.</param>
         /// <returns>A task object representing the asynchronous operation.</returns>
-        /// <exception cref="ArgumentNullException">If <paramref name="url"/> is null.</exception>
+        /// <exception cref="ArgumentNullException">If <paramref name="url"/> is <see langword="null"/>.</exception>
         Task GoToUrlAsync(string url);
 
         /// <summary>
@@ -90,7 +90,7 @@ public interface INavigation
         /// should the underlying page change while your test is executing the results of
         /// future calls against this interface will be against the freshly loaded page.
         /// </remarks>
-        /// <exception cref="ArgumentNullException">If <paramref name="url"/> is null.</exception>
+        /// <exception cref="ArgumentNullException">If <paramref name="url"/> is <see langword="null"/>.</exception>
         void GoToUrl(Uri url);
 
         /// <summary>
@@ -98,7 +98,7 @@ public interface INavigation
         /// </summary>
         /// <param name="url">Uri object of where you want the browser to go.</param>
         /// <returns>A task object representing the asynchronous operation.</returns>
-        /// <exception cref="ArgumentNullException">If <paramref name="url"/> is null.</exception>
+        /// <exception cref="ArgumentNullException">If <paramref name="url"/> is <see langword="null"/>.</exception>
         Task GoToUrlAsync(Uri url);
 
         /// <summary>
diff --git a/dotnet/src/webdriver/IOptions.cs b/dotnet/src/webdriver/IOptions.cs
index 78fd14514ba37..6c704000879e2 100644
--- a/dotnet/src/webdriver/IOptions.cs
+++ b/dotnet/src/webdriver/IOptions.cs
@@ -17,6 +17,8 @@
 // under the License.
 // </copyright>
 
+#nullable enable
+
 namespace OpenQA.Selenium
 {
     /// <summary>
diff --git a/dotnet/src/webdriver/ITimeouts.cs b/dotnet/src/webdriver/ITimeouts.cs
index 2e39ace5227f4..a0a4594e6088e 100644
--- a/dotnet/src/webdriver/ITimeouts.cs
+++ b/dotnet/src/webdriver/ITimeouts.cs
@@ -19,6 +19,8 @@
 
 using System;
 
+#nullable enable
+
 namespace OpenQA.Selenium
 {
     /// <summary>
diff --git a/dotnet/src/webdriver/IWindow.cs b/dotnet/src/webdriver/IWindow.cs
index c09ddd7341b22..e5202ed629319 100644
--- a/dotnet/src/webdriver/IWindow.cs
+++ b/dotnet/src/webdriver/IWindow.cs
@@ -19,6 +19,8 @@
 
 using System.Drawing;
 
+#nullable enable
+
 namespace OpenQA.Selenium
 {
     /// <summary>
diff --git a/dotnet/src/webdriver/Navigator.cs b/dotnet/src/webdriver/Navigator.cs
index 44604094058a2..4e50ec8ee8d29 100644
--- a/dotnet/src/webdriver/Navigator.cs
+++ b/dotnet/src/webdriver/Navigator.cs
@@ -86,7 +86,7 @@ public async Task ForwardAsync()
         /// Navigate to a url.
         /// </summary>
         /// <param name="url">String of where you want the browser to go to</param>
-        /// <exception cref="ArgumentNullException">If <paramref name="url"/> is null.</exception>
+        /// <exception cref="ArgumentNullException">If <paramref name="url"/> is <see langword="null"/>.</exception>
         public void GoToUrl(string url)
         {
             Task.Run(async delegate
@@ -100,7 +100,7 @@ public void GoToUrl(string url)
         /// </summary>
         /// <param name="url">String of where you want the browser to go.</param>
         /// <returns>A task object representing the asynchronous operation.</returns>
-        /// <exception cref="ArgumentNullException">If <paramref name="url"/> is null.</exception>
+        /// <exception cref="ArgumentNullException">If <paramref name="url"/> is <see langword="null"/>.</exception>
         public async Task GoToUrlAsync(string url)
         {
             if (url == null)
@@ -119,7 +119,7 @@ public async Task GoToUrlAsync(string url)
         /// Navigate to a url.
         /// </summary>
         /// <param name="url">Uri object of where you want the browser to go.</param>
-        /// <exception cref="ArgumentNullException">If <paramref name="url"/> is null.</exception>
+        /// <exception cref="ArgumentNullException">If <paramref name="url"/> is <see langword="null"/>.</exception>
         public void GoToUrl(Uri url)
         {
             Task.Run(async delegate
@@ -133,7 +133,7 @@ public void GoToUrl(Uri url)
         /// </summary>
         /// <param name="url">Uri object of where you want the browser to go.</param>
         /// <returns>A task object representing the asynchronous operation.</returns>
-        /// <exception cref="ArgumentNullException">If <paramref name="url"/> is null.</exception>
+        /// <exception cref="ArgumentNullException">If <paramref name="url"/> is <see langword="null"/>.</exception>
         public async Task GoToUrlAsync(Uri url)
         {
             if (url == null)
diff --git a/dotnet/src/webdriver/OptionsManager.cs b/dotnet/src/webdriver/OptionsManager.cs
index 4fc01194dc1c5..b7c4b85c1adb0 100644
--- a/dotnet/src/webdriver/OptionsManager.cs
+++ b/dotnet/src/webdriver/OptionsManager.cs
@@ -17,14 +17,16 @@
 // under the License.
 // </copyright>
 
+#nullable enable
+
 namespace OpenQA.Selenium
 {
     /// <summary>
     /// Provides a mechanism for setting options needed for the driver during the test.
     /// </summary>
-    internal class OptionsManager : IOptions
+    internal sealed class OptionsManager : IOptions
     {
-        private WebDriver driver;
+        private readonly WebDriver driver;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="OptionsManager"/> class
@@ -32,34 +34,25 @@ internal class OptionsManager : IOptions
         /// <param name="driver">Instance of the driver currently in use</param>
         public OptionsManager(WebDriver driver)
         {
-            this.driver = driver;
+            this.driver = driver ?? throw new System.ArgumentNullException(nameof(driver));
         }
 
         /// <summary>
         /// Gets an object allowing the user to manipulate cookies on the page.
         /// </summary>
-        public ICookieJar Cookies
-        {
-            get { return new CookieJar(this.driver); }
-        }
+        public ICookieJar Cookies => new CookieJar(this.driver);
 
         /// <summary>
         /// Gets an object allowing the user to manipulate the currently-focused browser window.
         /// </summary>
         /// <remarks>"Currently-focused" is defined as the browser window having the window handle
         /// returned when IWebDriver.CurrentWindowHandle is called.</remarks>
-        public IWindow Window
-        {
-            get { return new Window(this.driver); }
-        }
+        public IWindow Window => new Window(this.driver);
 
         /// <summary>
         /// Gets an object allowing the user to examine the logs of the current driver instance.
         /// </summary>
-        public ILogs Logs
-        {
-            get { return new Logs(this.driver); }
-        }
+        public ILogs Logs => new Logs(this.driver);
 
         /// <summary>
         /// Provides access to the timeouts defined for this driver.
@@ -70,9 +63,6 @@ public ITimeouts Timeouts()
             return new Timeouts(this.driver);
         }
 
-        public INetwork Network
-        {
-            get { return this.driver.Network; }
-        }
+        public INetwork Network => this.driver.Network;
     }
 }
diff --git a/dotnet/src/webdriver/Timeouts.cs b/dotnet/src/webdriver/Timeouts.cs
index 63422d21db6f9..b0f5882a7642d 100644
--- a/dotnet/src/webdriver/Timeouts.cs
+++ b/dotnet/src/webdriver/Timeouts.cs
@@ -21,6 +21,8 @@
 using System.Collections.Generic;
 using System.Globalization;
 
+#nullable enable
+
 namespace OpenQA.Selenium
 {
     /// <summary>
@@ -33,11 +35,11 @@ internal class Timeouts : ITimeouts
         private const string PageLoadTimeoutName = "pageLoad";
         private const string LegacyPageLoadTimeoutName = "page load";
 
-        private readonly TimeSpan DefaultImplicitWaitTimeout = TimeSpan.FromSeconds(0);
-        private readonly TimeSpan DefaultAsyncScriptTimeout = TimeSpan.FromSeconds(30);
-        private readonly TimeSpan DefaultPageLoadTimeout = TimeSpan.FromSeconds(300);
+        private static readonly TimeSpan DefaultImplicitWaitTimeout = TimeSpan.FromSeconds(0);
+        private static readonly TimeSpan DefaultAsyncScriptTimeout = TimeSpan.FromSeconds(30);
+        private static readonly TimeSpan DefaultPageLoadTimeout = TimeSpan.FromSeconds(300);
 
-        private WebDriver driver;
+        private readonly WebDriver driver;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="Timeouts"/> class
@@ -45,7 +47,7 @@ internal class Timeouts : ITimeouts
         /// <param name="driver">The driver that is currently in use</param>
         public Timeouts(WebDriver driver)
         {
-            this.driver = driver;
+            this.driver = driver ?? throw new ArgumentNullException(nameof(driver));
         }
 
         /// <summary>
@@ -70,8 +72,8 @@ public Timeouts(WebDriver driver)
         /// </remarks>
         public TimeSpan ImplicitWait
         {
-            get { return this.ExecuteGetTimeout(ImplicitTimeoutName); }
-            set { this.ExecuteSetTimeout(ImplicitTimeoutName, value); }
+            get => this.ExecuteGetTimeout(ImplicitTimeoutName);
+            set => this.ExecuteSetTimeout(ImplicitTimeoutName, value);
         }
 
         /// <summary>
@@ -87,8 +89,8 @@ public TimeSpan ImplicitWait
         /// </remarks>
         public TimeSpan AsynchronousJavaScript
         {
-            get { return this.ExecuteGetTimeout(AsyncScriptTimeoutName); }
-            set { this.ExecuteSetTimeout(AsyncScriptTimeoutName, value); }
+            get => this.ExecuteGetTimeout(AsyncScriptTimeoutName);
+            set => this.ExecuteSetTimeout(AsyncScriptTimeoutName, value);
         }
 
         /// <summary>
@@ -103,29 +105,21 @@ public TimeSpan AsynchronousJavaScript
         /// </remarks>
         public TimeSpan PageLoad
         {
-            get
-            {
-                string timeoutName = PageLoadTimeoutName;
-                return this.ExecuteGetTimeout(timeoutName);
-            }
-
-            set
-            {
-                string timeoutName = PageLoadTimeoutName;
-                this.ExecuteSetTimeout(timeoutName, value);
-            }
+            get => this.ExecuteGetTimeout(PageLoadTimeoutName);
+            set => this.ExecuteSetTimeout(PageLoadTimeoutName, value);
         }
 
         private TimeSpan ExecuteGetTimeout(string timeoutType)
         {
             Response commandResponse = this.driver.InternalExecute(DriverCommand.GetTimeouts, null);
-            Dictionary<string, object> responseValue = (Dictionary<string, object>)commandResponse.Value;
-            if (!responseValue.ContainsKey(timeoutType))
+
+            Dictionary<string, object?> responseValue = (Dictionary<string, object?>)commandResponse.Value!;
+            if (!responseValue.TryGetValue(timeoutType, out object? timeout))
             {
                 throw new WebDriverException("Specified timeout type not defined");
             }
 
-            return TimeSpan.FromMilliseconds(Convert.ToDouble(responseValue[timeoutType], CultureInfo.InvariantCulture));
+            return TimeSpan.FromMilliseconds(Convert.ToDouble(timeout, CultureInfo.InvariantCulture));
         }
 
         private void ExecuteSetTimeout(string timeoutType, TimeSpan timeToWait)
@@ -149,6 +143,7 @@ private void ExecuteSetTimeout(string timeoutType, TimeSpan timeToWait)
 
             Dictionary<string, object> parameters = new Dictionary<string, object>();
             parameters.Add(timeoutType, Convert.ToInt64(milliseconds));
+
             this.driver.InternalExecute(DriverCommand.SetTimeouts, parameters);
         }
     }
diff --git a/dotnet/src/webdriver/Window.cs b/dotnet/src/webdriver/Window.cs
index 6283f1ba3ef77..c856306bb668b 100644
--- a/dotnet/src/webdriver/Window.cs
+++ b/dotnet/src/webdriver/Window.cs
@@ -22,12 +22,14 @@
 using System.Drawing;
 using System.Globalization;
 
+#nullable enable
+
 namespace OpenQA.Selenium
 {
     /// <summary>
     /// Defines the interface through which the user can manipulate the browser window.
     /// </summary>
-    internal class Window : IWindow
+    internal sealed class Window : IWindow
     {
         private WebDriver driver;
 
@@ -37,7 +39,7 @@ internal class Window : IWindow
         /// <param name="driver">Instance of the driver currently in use</param>
         public Window(WebDriver driver)
         {
-            this.driver = driver;
+            this.driver = driver ?? throw new ArgumentNullException(nameof(driver));
         }
 
         /// <summary>
@@ -48,12 +50,12 @@ public Point Position
         {
             get
             {
-                Response commandResponse;
-                commandResponse = this.driver.InternalExecute(DriverCommand.GetWindowRect, null);
+                Response commandResponse = this.driver.InternalExecute(DriverCommand.GetWindowRect, null);
 
-                Dictionary<string, object> rawPosition = (Dictionary<string, object>)commandResponse.Value;
+                Dictionary<string, object?> rawPosition = (Dictionary<string, object?>)commandResponse.Value!;
                 int x = Convert.ToInt32(rawPosition["x"], CultureInfo.InvariantCulture);
                 int y = Convert.ToInt32(rawPosition["y"], CultureInfo.InvariantCulture);
+
                 return new Point(x, y);
             }
 
@@ -74,11 +76,12 @@ public Size Size
         {
             get
             {
-                Response commandResponse;
-                commandResponse = this.driver.InternalExecute(DriverCommand.GetWindowRect, null);
-                Dictionary<string, object> rawPosition = (Dictionary<string, object>)commandResponse.Value;
+                Response commandResponse = this.driver.InternalExecute(DriverCommand.GetWindowRect, null);
+
+                Dictionary<string, object?> rawPosition = (Dictionary<string, object?>)commandResponse.Value!;
                 int height = Convert.ToInt32(rawPosition["height"], CultureInfo.InvariantCulture);
                 int width = Convert.ToInt32(rawPosition["width"], CultureInfo.InvariantCulture);
+
                 return new Size(width, height);
             }
 
@@ -96,8 +99,7 @@ public Size Size
         /// </summary>
         public void Maximize()
         {
-            Dictionary<string, object> parameters = null;
-            this.driver.InternalExecute(DriverCommand.MaximizeWindow, parameters);
+            this.driver.InternalExecute(DriverCommand.MaximizeWindow, null);
         }
 
         /// <summary>
@@ -105,8 +107,7 @@ public void Maximize()
         /// </summary>
         public void Minimize()
         {
-            Dictionary<string, object> parameters = null;
-            this.driver.InternalExecute(DriverCommand.MinimizeWindow, parameters);
+            this.driver.InternalExecute(DriverCommand.MinimizeWindow, null);
         }
 
         /// <summary>
@@ -114,8 +115,7 @@ public void Minimize()
         /// </summary>
         public void FullScreen()
         {
-            Dictionary<string, object> parameters = null;
-            this.driver.InternalExecute(DriverCommand.FullScreenWindow, parameters);
+            this.driver.InternalExecute(DriverCommand.FullScreenWindow, null);
         }
     }
 }