diff --git a/dotnet/src/webdriver/CookieJar.cs b/dotnet/src/webdriver/CookieJar.cs
index e4f681e11908a..8ae324fa6961f 100644
--- a/dotnet/src/webdriver/CookieJar.cs
+++ b/dotnet/src/webdriver/CookieJar.cs
@@ -21,64 +21,92 @@
 using System.Collections.Generic;
 using System.Collections.ObjectModel;
 
+#nullable enable
+
 namespace OpenQA.Selenium
 {
-    /// <summary>
-    /// Defines an interface allowing the user to manipulate cookies on the current page.
-    /// </summary>
-    internal class CookieJar : ICookieJar
+    internal sealed class CookieJar(WebDriver driver) : ICookieJar
     {
-        private WebDriver driver;
-
-        /// <summary>
-        /// Initializes a new instance of the <see cref="CookieJar"/> class.
-        /// </summary>
-        /// <param name="driver">The driver that is currently in use</param>
-        public CookieJar(WebDriver driver)
-        {
-            this.driver = driver;
-        }
-
         /// <summary>
         /// Gets all cookies defined for the current page.
         /// </summary>
         public ReadOnlyCollection<Cookie> AllCookies
         {
-            get { return this.GetAllCookies(); }
+            get
+            {
+                Response response = driver.InternalExecute(DriverCommand.GetAllCookies, new Dictionary<string, object>());
+
+                try
+                {
+                    List<Cookie> toReturn = new List<Cookie>();
+                    if (response.Value is object?[] cookies)
+                    {
+                        foreach (object? rawCookie in cookies)
+                        {
+                            if (rawCookie != null)
+                            {
+                                Cookie newCookie = Cookie.FromDictionary((Dictionary<string, object?>)rawCookie);
+                                toReturn.Add(newCookie);
+                            }
+                        }
+                    }
+
+                    return new ReadOnlyCollection<Cookie>(toReturn);
+                }
+                catch (Exception e)
+                {
+                    throw new WebDriverException("Unexpected problem getting cookies", e);
+                }
+            }
         }
 
         /// <summary>
         /// Method for creating a cookie in the browser
         /// </summary>
         /// <param name="cookie"><see cref="Cookie"/> that represents a cookie in the browser</param>
+        /// <exception cref="ArgumentNullException">If <paramref name="cookie"/> is <see langword="null"/>.</exception>
         public void AddCookie(Cookie cookie)
         {
+            if (cookie is null)
+            {
+                throw new ArgumentNullException(nameof(cookie));
+            }
+
             Dictionary<string, object> parameters = new Dictionary<string, object>();
             parameters.Add("cookie", cookie);
-            this.driver.InternalExecute(DriverCommand.AddCookie, parameters);
+            driver.InternalExecute(DriverCommand.AddCookie, parameters);
         }
 
         /// <summary>
         /// Delete the cookie by passing in the name of the cookie
         /// </summary>
         /// <param name="name">The name of the cookie that is in the browser</param>
+        /// <exception cref="ArgumentNullException">If <paramref name="name"/> is <see langword="null"/>.</exception>
         public void DeleteCookieNamed(string name)
         {
+            if (name is null)
+            {
+                throw new ArgumentNullException(nameof(name));
+            }
+
             Dictionary<string, object> parameters = new Dictionary<string, object>();
             parameters.Add("name", name);
-            this.driver.InternalExecute(DriverCommand.DeleteCookie, parameters);
+            driver.InternalExecute(DriverCommand.DeleteCookie, parameters);
         }
 
         /// <summary>
         /// Delete a cookie in the browser by passing in a copy of a cookie
         /// </summary>
         /// <param name="cookie">An object that represents a copy of the cookie that needs to be deleted</param>
+        /// <exception cref="ArgumentNullException">If <paramref name="cookie"/> is <see langword="null"/>.</exception>
         public void DeleteCookie(Cookie cookie)
         {
-            if (cookie != null)
+            if (cookie is null)
             {
-                this.DeleteCookieNamed(cookie.Name);
+                throw new ArgumentNullException(nameof(cookie));
             }
+
+            this.DeleteCookieNamed(cookie.Name);
         }
 
         /// <summary>
@@ -86,63 +114,32 @@ public void DeleteCookie(Cookie cookie)
         /// </summary>
         public void DeleteAllCookies()
         {
-            this.driver.InternalExecute(DriverCommand.DeleteAllCookies, null);
+            driver.InternalExecute(DriverCommand.DeleteAllCookies, null);
         }
 
         /// <summary>
         /// Method for returning a getting a cookie by name
         /// </summary>
         /// <param name="name">name of the cookie that needs to be returned</param>
-        /// <returns>A Cookie from the name</returns>
-        public Cookie GetCookieNamed(string name)
+        /// <returns>A Cookie from the name; or <see langword="null"/> if not found.</returns>
+        public Cookie? GetCookieNamed(string name)
         {
-            Cookie cookieToReturn = null;
-            if (name != null)
+            if (name is null)
             {
-                ReadOnlyCollection<Cookie> allCookies = this.AllCookies;
-                foreach (Cookie currentCookie in allCookies)
-                {
-                    if (name.Equals(currentCookie.Name))
-                    {
-                        cookieToReturn = currentCookie;
-                        break;
-                    }
-                }
+                throw new ArgumentNullException(nameof(name));
             }
 
-            return cookieToReturn;
-        }
 
-        /// <summary>
-        /// Method for getting a Collection of Cookies that are present in the browser
-        /// </summary>
-        /// <returns>ReadOnlyCollection of Cookies in the browser</returns>
-        private ReadOnlyCollection<Cookie> GetAllCookies()
-        {
-            List<Cookie> toReturn = new List<Cookie>();
-            object returned = this.driver.InternalExecute(DriverCommand.GetAllCookies, new Dictionary<string, object>()).Value;
-
-            try
+            foreach (Cookie currentCookie in this.AllCookies)
             {
-                object[] cookies = returned as object[];
-                if (cookies != null)
+                if (name.Equals(currentCookie.Name))
                 {
-                    foreach (object rawCookie in cookies)
-                    {
-                        Dictionary<string, object> cookieDictionary = rawCookie as Dictionary<string, object>;
-                        if (rawCookie != null)
-                        {
-                            toReturn.Add(Cookie.FromDictionary(cookieDictionary));
-                        }
-                    }
+                    return currentCookie;
                 }
 
-                return new ReadOnlyCollection<Cookie>(toReturn);
-            }
-            catch (Exception e)
-            {
-                throw new WebDriverException("Unexpected problem getting cookies", e);
             }
+
+            return null;
         }
     }
 }
diff --git a/dotnet/src/webdriver/ICookieJar.cs b/dotnet/src/webdriver/ICookieJar.cs
index a27c472a78c41..07594bf8f3173 100644
--- a/dotnet/src/webdriver/ICookieJar.cs
+++ b/dotnet/src/webdriver/ICookieJar.cs
@@ -17,8 +17,11 @@
 // under the License.
 // </copyright>
 
+using System;
 using System.Collections.ObjectModel;
 
+#nullable enable
+
 namespace OpenQA.Selenium
 {
     /// <summary>
@@ -35,6 +38,7 @@ public interface ICookieJar
         /// Adds a cookie to the current page.
         /// </summary>
         /// <param name="cookie">The <see cref="Cookie"/> object to be added.</param>
+        /// <exception cref="ArgumentNullException">If <paramref name="cookie"/> is <see langword="null"/>.</exception>
         void AddCookie(Cookie cookie);
 
         /// <summary>
@@ -43,18 +47,21 @@ public interface ICookieJar
         /// <param name="name">The name of the cookie to retrieve.</param>
         /// <returns>The <see cref="Cookie"/> containing the name. Returns <see langword="null"/>
         /// if no cookie with the specified name is found.</returns>
-        Cookie GetCookieNamed(string name);
+        /// <exception cref="ArgumentNullException">If <paramref name="name"/> is <see langword="null"/>.</exception>
+        Cookie? GetCookieNamed(string name);
 
         /// <summary>
         /// Deletes the specified cookie from the page.
         /// </summary>
         /// <param name="cookie">The <see cref="Cookie"/> to be deleted.</param>
+        /// <exception cref="ArgumentNullException">If <paramref name="cookie"/> is <see langword="null"/>.</exception>
         void DeleteCookie(Cookie cookie);
 
         /// <summary>
         /// Deletes the cookie with the specified name from the page.
         /// </summary>
         /// <param name="name">The name of the cookie to be deleted.</param>
+        /// <exception cref="ArgumentNullException">If <paramref name="name"/> is <see langword="null"/>.</exception>
         void DeleteCookieNamed(string name);
 
         /// <summary>