diff --git a/dotnet/src/webdriver/DevTools/Network.cs b/dotnet/src/webdriver/DevTools/Network.cs
index 64f3cce08750a..5b6b021e6596c 100644
--- a/dotnet/src/webdriver/DevTools/Network.cs
+++ b/dotnet/src/webdriver/DevTools/Network.cs
@@ -17,9 +17,12 @@
 // under the License.
 // </copyright>
 
+using System;
 using System.Linq;
 using System.Threading.Tasks;
 
+#nullable enable
+
 namespace OpenQA.Selenium.DevTools
 {
     /// <summary>
@@ -30,17 +33,17 @@ public abstract class Network
         /// <summary>
         /// Occurs when a network request requires authorization.
         /// </summary>
-        public event AsyncEventHandler<AuthRequiredEventArgs> AuthRequired;
+        public event AsyncEventHandler<AuthRequiredEventArgs>? AuthRequired;
 
         /// <summary>
         /// Occurs when a network request is intercepted.
         /// </summary>
-        public event AsyncEventHandler<RequestPausedEventArgs> RequestPaused;
+        public event AsyncEventHandler<RequestPausedEventArgs>? RequestPaused;
 
         /// <summary>
         /// Occurs when a network response is received.
         /// </summary>
-        public event AsyncEventHandler<ResponsePausedEventArgs> ResponsePaused;
+        public event AsyncEventHandler<ResponsePausedEventArgs>? ResponsePaused;
 
         /// <summary>
         /// Asynchronously disables network caching.
@@ -61,7 +64,7 @@ public abstract class Network
         public abstract Task EnableNetwork();
 
         /// <summary>
-        /// Asynchronously diables the fetch domain.
+        /// Asynchronously disables the fetch domain.
         /// </summary>
         /// <returns>A task that represents the asynchronous operation.</returns>
         public abstract Task DisableNetwork();
@@ -79,7 +82,7 @@ public abstract class Network
         /// <returns>A task that represents the asynchronous operation.</returns>
         public async Task SetUserAgentOverride(string userAgent)
         {
-            await SetUserAgentOverride(new UserAgent() { UserAgentString = userAgent }).ConfigureAwait(false);
+            await SetUserAgentOverride(new UserAgent(userAgent)).ConfigureAwait(false);
         }
 
         /// <summary>
@@ -87,10 +90,11 @@ public async Task SetUserAgentOverride(string userAgent)
         /// </summary>
         /// <param name="userAgent">A <see cref="UserAgent"/> object containing the user agent values to override.</param>
         /// <returns>A task that represents the asynchronous operation.</returns>
+        /// <exception cref="ArgumentNullException">If <paramref name="userAgent"/> is null.</exception>
         public abstract Task SetUserAgentOverride(UserAgent userAgent);
 
         /// <summary>
-        /// Asynchronously diables the fetch domain.
+        /// Asynchronously disables the fetch domain.
         /// </summary>
         /// <returns>A task that represents the asynchronous operation.</returns>
         public abstract Task DisableFetch();
@@ -100,6 +104,7 @@ public async Task SetUserAgentOverride(string userAgent)
         /// </summary>
         /// <param name="requestData">The <see cref="HttpRequestData"/> of the request.</param>
         /// <returns>A task that represents the asynchronous operation.</returns>
+        /// <exception cref="ArgumentNullException">If <paramref name="requestData"/> is <see langword="null"/>.</exception>
         public abstract Task ContinueRequest(HttpRequestData requestData);
 
         /// <summary>
@@ -108,13 +113,15 @@ public async Task SetUserAgentOverride(string userAgent)
         /// <param name="requestData">The <see cref="HttpRequestData"/> of the request.</param>
         /// <param name="responseData">The <see cref="HttpResponseData"/> with which to respond to the request</param>
         /// <returns>A task that represents the asynchronous operation.</returns>
+        /// <exception cref="ArgumentNullException">If <paramref name="requestData"/> or <paramref name="responseData"/> are <see langword="null"/>.</exception>
         public abstract Task ContinueRequestWithResponse(HttpRequestData requestData, HttpResponseData responseData);
 
         /// <summary>
-        /// Asynchronously contines an intercepted network request without modification.
+        /// Asynchronously continues an intercepted network request without modification.
         /// </summary>
         /// <param name="requestData">The <see cref="HttpRequestData"/> of the network request.</param>
         /// <returns>A task that represents the asynchronous operation.</returns>
+        /// <exception cref="ArgumentNullException">If <paramref name="requestData"/> is <see langword="null"/>.</exception>
         public abstract Task ContinueRequestWithoutModification(HttpRequestData requestData);
 
         /// <summary>
@@ -124,7 +131,7 @@ public async Task SetUserAgentOverride(string userAgent)
         /// <param name="userName">The user name with which to authenticate.</param>
         /// <param name="password">The password with which to authenticate.</param>
         /// <returns>A task that represents the asynchronous operation.</returns>
-        public abstract Task ContinueWithAuth(string requestId, string userName, string password);
+        public abstract Task ContinueWithAuth(string requestId, string? userName, string? password);
 
         /// <summary>
         /// Asynchronously cancels authorization of an intercepted network request.
@@ -138,6 +145,7 @@ public async Task SetUserAgentOverride(string userAgent)
         /// </summary>
         /// <param name="responseData">The <see cref="HttpResponseData"/> object to which to add the response body.</param>
         /// <returns>A task that represents the asynchronous operation.</returns>
+        /// <exception cref="ArgumentNullException">If <paramref name="responseData"/> is <see langword="null"/>.</exception>
         public abstract Task AddResponseBody(HttpResponseData responseData);
 
         /// <summary>
@@ -145,6 +153,7 @@ public async Task SetUserAgentOverride(string userAgent)
         /// </summary>
         /// <param name="responseData">The <see cref="HttpResponseData"/> of the network response.</param>
         /// <returns>A task that represents the asynchronous operation.</returns>
+        /// <exception cref="ArgumentNullException">If <paramref name="responseData"/> is <see langword="null"/>.</exception>
         public abstract Task ContinueResponseWithoutModification(HttpResponseData responseData);
 
         /// <summary>
@@ -200,7 +209,7 @@ protected virtual void OnResponsePaused(ResponsePausedEventArgs e)
 
         /// <returns>A task that represents the asynchronous operation.</returns>
         /// <summary>
-        /// Am asynchrounous delegate for handling network events.
+        /// Am asynchronous delegate for handling network events.
         /// </summary>
         /// <typeparam name="TEventArgs">The type of event args the event raises.</typeparam>
         /// <param name="sender">The sender of the event.</param>
diff --git a/dotnet/src/webdriver/DevTools/v130/V130Network.cs b/dotnet/src/webdriver/DevTools/v130/V130Network.cs
index 74be92a081246..8d8d7396776f5 100644
--- a/dotnet/src/webdriver/DevTools/v130/V130Network.cs
+++ b/dotnet/src/webdriver/DevTools/v130/V130Network.cs
@@ -24,6 +24,8 @@
 using System.Text;
 using System.Threading.Tasks;
 
+#nullable enable
+
 namespace OpenQA.Selenium.DevTools.V130
 {
     /// <summary>
@@ -39,10 +41,11 @@ public class V130Network : DevTools.Network
         /// </summary>
         /// <param name="network">The adapter for the Network domain.</param>
         /// <param name="fetch">The adapter for the Fetch domain.</param>
+        /// <exception cref="ArgumentNullException">If <paramref name="network"/> or <paramref name="fetch"/> are <see langword="null"/>.</exception>
         public V130Network(NetworkAdapter network, FetchAdapter fetch)
         {
-            this.network = network;
-            this.fetch = fetch;
+            this.network = network ?? throw new ArgumentNullException(nameof(network));
+            this.fetch = fetch ?? throw new ArgumentNullException(nameof(fetch));
             fetch.AuthRequired += OnFetchAuthRequired;
             fetch.RequestPaused += OnFetchRequestPaused;
         }
@@ -101,7 +104,7 @@ await fetch.Enable(new Fetch.EnableCommandSettings()
         }
 
         /// <summary>
-        /// Asynchronously diables the fetch domain.
+        /// Asynchronously disables the fetch domain.
         /// </summary>
         /// <returns>A task that represents the asynchronous operation.</returns>
         public override async Task DisableFetch()
@@ -114,8 +117,14 @@ public override async Task DisableFetch()
         /// </summary>
         /// <param name="userAgent">A <see cref="UserAgent"/> object containing the user agent values to override.</param>
         /// <returns>A task that represents the asynchronous operation.</returns>
+        /// <exception cref="ArgumentNullException">If <paramref name="userAgent"/> is null.</exception>
         public override async Task SetUserAgentOverride(UserAgent userAgent)
         {
+            if (userAgent is null)
+            {
+                throw new ArgumentNullException(nameof(userAgent));
+            }
+
             await network.SetUserAgentOverride(new SetUserAgentOverrideCommandSettings()
             {
                 UserAgent = userAgent.UserAgentString,
@@ -129,8 +138,14 @@ await network.SetUserAgentOverride(new SetUserAgentOverrideCommandSettings()
         /// </summary>
         /// <param name="requestData">The <see cref="HttpRequestData"/> of the request.</param>
         /// <returns>A task that represents the asynchronous operation.</returns>
+        /// <exception cref="ArgumentNullException">If <paramref name="requestData"/> is <see langword="null"/>.</exception>
         public override async Task ContinueRequest(HttpRequestData requestData)
         {
+            if (requestData is null)
+            {
+                throw new ArgumentNullException(nameof(requestData));
+            }
+
             var commandSettings = new ContinueRequestCommandSettings()
             {
                 RequestId = requestData.RequestId,
@@ -163,8 +178,19 @@ public override async Task ContinueRequest(HttpRequestData requestData)
         /// <param name="requestData">The <see cref="HttpRequestData"/> of the request.</param>
         /// <param name="responseData">The <see cref="HttpResponseData"/> with which to respond to the request</param>
         /// <returns>A task that represents the asynchronous operation.</returns>
+        /// <exception cref="ArgumentNullException">If <paramref name="requestData"/> or <paramref name="responseData"/> are <see langword="null"/>.</exception>
         public override async Task ContinueRequestWithResponse(HttpRequestData requestData, HttpResponseData responseData)
         {
+            if (requestData is null)
+            {
+                throw new ArgumentNullException(nameof(requestData));
+            }
+
+            if (responseData is null)
+            {
+                throw new ArgumentNullException(nameof(responseData));
+            }
+
             var commandSettings = new FulfillRequestCommandSettings()
             {
                 RequestId = requestData.RequestId,
@@ -196,12 +222,18 @@ public override async Task ContinueRequestWithResponse(HttpRequestData requestDa
         }
 
         /// <summary>
-        /// Asynchronously contines an intercepted network call without modification.
+        /// Asynchronously continues an intercepted network call without modification.
         /// </summary>
         /// <param name="requestData">The <see cref="HttpRequestData"/> of the network call.</param>
         /// <returns>A task that represents the asynchronous operation.</returns>
+        /// <exception cref="ArgumentNullException">If <paramref name="requestData"/> is <see langword="null"/>.</exception>
         public override async Task ContinueRequestWithoutModification(HttpRequestData requestData)
         {
+            if (requestData is null)
+            {
+                throw new ArgumentNullException(nameof(requestData));
+            }
+
             await fetch.ContinueRequest(new ContinueRequestCommandSettings() { RequestId = requestData.RequestId }).ConfigureAwait(false);
         }
 
@@ -212,7 +244,7 @@ public override async Task ContinueRequestWithoutModification(HttpRequestData re
         /// <param name="userName">The user name with which to authenticate.</param>
         /// <param name="password">The password with which to authenticate.</param>
         /// <returns>A task that represents the asynchronous operation.</returns>
-        public override async Task ContinueWithAuth(string requestId, string userName, string password)
+        public override async Task ContinueWithAuth(string requestId, string? userName, string? password)
         {
             await fetch.ContinueWithAuth(new ContinueWithAuthCommandSettings()
             {
@@ -248,8 +280,14 @@ await fetch.ContinueWithAuth(new ContinueWithAuthCommandSettings()
         /// </summary>
         /// <param name="responseData">The <see cref="HttpResponseData"/> object to which to add the response body.</param>
         /// <returns>A task that represents the asynchronous operation.</returns>
+        /// <exception cref="ArgumentNullException">If <paramref name="responseData"/> is <see langword="null"/>.</exception>
         public override async Task AddResponseBody(HttpResponseData responseData)
         {
+            if (responseData is null)
+            {
+                throw new ArgumentNullException(nameof(responseData));
+            }
+
             // If the response is a redirect, retrieving the body will throw an error in CDP.
             if (responseData.StatusCode < 300 || responseData.StatusCode > 399)
             {
@@ -273,12 +311,18 @@ public override async Task AddResponseBody(HttpResponseData responseData)
         /// </summary>
         /// <param name="responseData">The <see cref="HttpResponseData"/> of the network response.</param>
         /// <returns>A task that represents the asynchronous operation.</returns>
+        /// <exception cref="ArgumentNullException">If <paramref name="responseData"/> is <see langword="null"/>.</exception>
         public override async Task ContinueResponseWithoutModification(HttpResponseData responseData)
         {
+            if (responseData is null)
+            {
+                throw new ArgumentNullException(nameof(responseData));
+            }
+
             await fetch.ContinueResponse(new ContinueResponseCommandSettings() { RequestId = responseData.RequestId }).ConfigureAwait(false);
         }
 
-        private void OnFetchAuthRequired(object sender, Fetch.AuthRequiredEventArgs e)
+        private void OnFetchAuthRequired(object? sender, Fetch.AuthRequiredEventArgs e)
         {
             AuthRequiredEventArgs wrapped = new AuthRequiredEventArgs
             (
@@ -289,7 +333,7 @@ private void OnFetchAuthRequired(object sender, Fetch.AuthRequiredEventArgs e)
             this.OnAuthRequired(wrapped);
         }
 
-        private void OnFetchRequestPaused(object sender, Fetch.RequestPausedEventArgs e)
+        private void OnFetchRequestPaused(object? sender, Fetch.RequestPausedEventArgs e)
         {
             if (e.ResponseErrorReason == null && e.ResponseStatusCode == null)
             {
diff --git a/dotnet/src/webdriver/DevTools/v131/V131Network.cs b/dotnet/src/webdriver/DevTools/v131/V131Network.cs
index c8887543338be..a8c5e2447c9b8 100644
--- a/dotnet/src/webdriver/DevTools/v131/V131Network.cs
+++ b/dotnet/src/webdriver/DevTools/v131/V131Network.cs
@@ -24,6 +24,8 @@
 using System.Text;
 using System.Threading.Tasks;
 
+#nullable enable
+
 namespace OpenQA.Selenium.DevTools.V131
 {
     /// <summary>
@@ -39,10 +41,11 @@ public class V131Network : DevTools.Network
         /// </summary>
         /// <param name="network">The adapter for the Network domain.</param>
         /// <param name="fetch">The adapter for the Fetch domain.</param>
+        /// <exception cref="ArgumentNullException">If <paramref name="network"/> or <paramref name="fetch"/> are <see langword="null"/>.</exception>
         public V131Network(NetworkAdapter network, FetchAdapter fetch)
         {
-            this.network = network;
-            this.fetch = fetch;
+            this.network = network ?? throw new ArgumentNullException(nameof(network));
+            this.fetch = fetch ?? throw new ArgumentNullException(nameof(fetch));
             fetch.AuthRequired += OnFetchAuthRequired;
             fetch.RequestPaused += OnFetchRequestPaused;
         }
@@ -101,7 +104,7 @@ await fetch.Enable(new Fetch.EnableCommandSettings()
         }
 
         /// <summary>
-        /// Asynchronously diables the fetch domain.
+        /// Asynchronously disables the fetch domain.
         /// </summary>
         /// <returns>A task that represents the asynchronous operation.</returns>
         public override async Task DisableFetch()
@@ -114,8 +117,14 @@ public override async Task DisableFetch()
         /// </summary>
         /// <param name="userAgent">A <see cref="UserAgent"/> object containing the user agent values to override.</param>
         /// <returns>A task that represents the asynchronous operation.</returns>
+        /// <exception cref="ArgumentNullException">If <paramref name="userAgent"/> is null.</exception>
         public override async Task SetUserAgentOverride(UserAgent userAgent)
         {
+            if (userAgent is null)
+            {
+                throw new ArgumentNullException(nameof(userAgent));
+            }
+
             await network.SetUserAgentOverride(new SetUserAgentOverrideCommandSettings()
             {
                 UserAgent = userAgent.UserAgentString,
@@ -129,8 +138,14 @@ await network.SetUserAgentOverride(new SetUserAgentOverrideCommandSettings()
         /// </summary>
         /// <param name="requestData">The <see cref="HttpRequestData"/> of the request.</param>
         /// <returns>A task that represents the asynchronous operation.</returns>
+        /// <exception cref="ArgumentNullException">If <paramref name="requestData"/> is <see langword="null"/>.</exception>
         public override async Task ContinueRequest(HttpRequestData requestData)
         {
+            if (requestData is null)
+            {
+                throw new ArgumentNullException(nameof(requestData));
+            }
+
             var commandSettings = new ContinueRequestCommandSettings()
             {
                 RequestId = requestData.RequestId,
@@ -163,8 +178,19 @@ public override async Task ContinueRequest(HttpRequestData requestData)
         /// <param name="requestData">The <see cref="HttpRequestData"/> of the request.</param>
         /// <param name="responseData">The <see cref="HttpResponseData"/> with which to respond to the request</param>
         /// <returns>A task that represents the asynchronous operation.</returns>
+        /// <exception cref="ArgumentNullException">If <paramref name="requestData"/> or <paramref name="responseData"/> are <see langword="null"/>.</exception>
         public override async Task ContinueRequestWithResponse(HttpRequestData requestData, HttpResponseData responseData)
         {
+            if (requestData is null)
+            {
+                throw new ArgumentNullException(nameof(requestData));
+            }
+
+            if (responseData is null)
+            {
+                throw new ArgumentNullException(nameof(responseData));
+            }
+
             var commandSettings = new FulfillRequestCommandSettings()
             {
                 RequestId = requestData.RequestId,
@@ -196,12 +222,18 @@ public override async Task ContinueRequestWithResponse(HttpRequestData requestDa
         }
 
         /// <summary>
-        /// Asynchronously contines an intercepted network call without modification.
+        /// Asynchronously continues an intercepted network call without modification.
         /// </summary>
         /// <param name="requestData">The <see cref="HttpRequestData"/> of the network call.</param>
         /// <returns>A task that represents the asynchronous operation.</returns>
+        /// <exception cref="ArgumentNullException">If <paramref name="requestData"/> is <see langword="null"/>.</exception>
         public override async Task ContinueRequestWithoutModification(HttpRequestData requestData)
         {
+            if (requestData is null)
+            {
+                throw new ArgumentNullException(nameof(requestData));
+            }
+
             await fetch.ContinueRequest(new ContinueRequestCommandSettings() { RequestId = requestData.RequestId }).ConfigureAwait(false);
         }
 
@@ -212,7 +244,7 @@ public override async Task ContinueRequestWithoutModification(HttpRequestData re
         /// <param name="userName">The user name with which to authenticate.</param>
         /// <param name="password">The password with which to authenticate.</param>
         /// <returns>A task that represents the asynchronous operation.</returns>
-        public override async Task ContinueWithAuth(string requestId, string userName, string password)
+        public override async Task ContinueWithAuth(string requestId, string? userName, string? password)
         {
             await fetch.ContinueWithAuth(new ContinueWithAuthCommandSettings()
             {
@@ -248,8 +280,14 @@ await fetch.ContinueWithAuth(new ContinueWithAuthCommandSettings()
         /// </summary>
         /// <param name="responseData">The <see cref="HttpResponseData"/> object to which to add the response body.</param>
         /// <returns>A task that represents the asynchronous operation.</returns>
+        /// <exception cref="ArgumentNullException">If <paramref name="responseData"/> is <see langword="null"/>.</exception>
         public override async Task AddResponseBody(HttpResponseData responseData)
         {
+            if (responseData is null)
+            {
+                throw new ArgumentNullException(nameof(responseData));
+            }
+
             // If the response is a redirect, retrieving the body will throw an error in CDP.
             if (responseData.StatusCode < 300 || responseData.StatusCode > 399)
             {
@@ -273,12 +311,18 @@ public override async Task AddResponseBody(HttpResponseData responseData)
         /// </summary>
         /// <param name="responseData">The <see cref="HttpResponseData"/> of the network response.</param>
         /// <returns>A task that represents the asynchronous operation.</returns>
+        /// <exception cref="ArgumentNullException">If <paramref name="responseData"/> is <see langword="null"/>.</exception>
         public override async Task ContinueResponseWithoutModification(HttpResponseData responseData)
         {
+            if (responseData is null)
+            {
+                throw new ArgumentNullException(nameof(responseData));
+            }
+
             await fetch.ContinueResponse(new ContinueResponseCommandSettings() { RequestId = responseData.RequestId }).ConfigureAwait(false);
         }
 
-        private void OnFetchAuthRequired(object sender, Fetch.AuthRequiredEventArgs e)
+        private void OnFetchAuthRequired(object? sender, Fetch.AuthRequiredEventArgs e)
         {
             AuthRequiredEventArgs wrapped = new AuthRequiredEventArgs
             (
@@ -289,7 +333,7 @@ private void OnFetchAuthRequired(object sender, Fetch.AuthRequiredEventArgs e)
             this.OnAuthRequired(wrapped);
         }
 
-        private void OnFetchRequestPaused(object sender, Fetch.RequestPausedEventArgs e)
+        private void OnFetchRequestPaused(object? sender, Fetch.RequestPausedEventArgs e)
         {
             if (e.ResponseErrorReason == null && e.ResponseStatusCode == null)
             {
diff --git a/dotnet/src/webdriver/DevTools/v132/V132Network.cs b/dotnet/src/webdriver/DevTools/v132/V132Network.cs
index 6acaf24d58472..629a91a018cfb 100644
--- a/dotnet/src/webdriver/DevTools/v132/V132Network.cs
+++ b/dotnet/src/webdriver/DevTools/v132/V132Network.cs
@@ -24,6 +24,8 @@
 using System.Text;
 using System.Threading.Tasks;
 
+#nullable enable
+
 namespace OpenQA.Selenium.DevTools.V132
 {
     /// <summary>
@@ -39,10 +41,11 @@ public class V132Network : DevTools.Network
         /// </summary>
         /// <param name="network">The adapter for the Network domain.</param>
         /// <param name="fetch">The adapter for the Fetch domain.</param>
+        /// <exception cref="ArgumentNullException">If <paramref name="network"/> or <paramref name="fetch"/> are <see langword="null"/>.</exception>
         public V132Network(NetworkAdapter network, FetchAdapter fetch)
         {
-            this.network = network;
-            this.fetch = fetch;
+            this.network = network ?? throw new ArgumentNullException(nameof(network));
+            this.fetch = fetch ?? throw new ArgumentNullException(nameof(fetch));
             fetch.AuthRequired += OnFetchAuthRequired;
             fetch.RequestPaused += OnFetchRequestPaused;
         }
@@ -101,7 +104,7 @@ await fetch.Enable(new Fetch.EnableCommandSettings()
         }
 
         /// <summary>
-        /// Asynchronously diables the fetch domain.
+        /// Asynchronously disables the fetch domain.
         /// </summary>
         /// <returns>A task that represents the asynchronous operation.</returns>
         public override async Task DisableFetch()
@@ -114,8 +117,14 @@ public override async Task DisableFetch()
         /// </summary>
         /// <param name="userAgent">A <see cref="UserAgent"/> object containing the user agent values to override.</param>
         /// <returns>A task that represents the asynchronous operation.</returns>
+        /// <exception cref="ArgumentNullException">If <paramref name="userAgent"/> is null.</exception>
         public override async Task SetUserAgentOverride(UserAgent userAgent)
         {
+            if (userAgent is null)
+            {
+                throw new ArgumentNullException(nameof(userAgent));
+            }
+
             await network.SetUserAgentOverride(new SetUserAgentOverrideCommandSettings()
             {
                 UserAgent = userAgent.UserAgentString,
@@ -129,8 +138,14 @@ await network.SetUserAgentOverride(new SetUserAgentOverrideCommandSettings()
         /// </summary>
         /// <param name="requestData">The <see cref="HttpRequestData"/> of the request.</param>
         /// <returns>A task that represents the asynchronous operation.</returns>
+        /// <exception cref="ArgumentNullException">If <paramref name="requestData"/> is <see langword="null"/>.</exception>
         public override async Task ContinueRequest(HttpRequestData requestData)
         {
+            if (requestData is null)
+            {
+                throw new ArgumentNullException(nameof(requestData));
+            }
+
             var commandSettings = new ContinueRequestCommandSettings()
             {
                 RequestId = requestData.RequestId,
@@ -163,8 +178,19 @@ public override async Task ContinueRequest(HttpRequestData requestData)
         /// <param name="requestData">The <see cref="HttpRequestData"/> of the request.</param>
         /// <param name="responseData">The <see cref="HttpResponseData"/> with which to respond to the request</param>
         /// <returns>A task that represents the asynchronous operation.</returns>
+        /// <exception cref="ArgumentNullException">If <paramref name="requestData"/> or <paramref name="responseData"/> are <see langword="null"/>.</exception>
         public override async Task ContinueRequestWithResponse(HttpRequestData requestData, HttpResponseData responseData)
         {
+            if (requestData is null)
+            {
+                throw new ArgumentNullException(nameof(requestData));
+            }
+
+            if (responseData is null)
+            {
+                throw new ArgumentNullException(nameof(responseData));
+            }
+
             var commandSettings = new FulfillRequestCommandSettings()
             {
                 RequestId = requestData.RequestId,
@@ -196,12 +222,18 @@ public override async Task ContinueRequestWithResponse(HttpRequestData requestDa
         }
 
         /// <summary>
-        /// Asynchronously contines an intercepted network call without modification.
+        /// Asynchronously continues an intercepted network call without modification.
         /// </summary>
         /// <param name="requestData">The <see cref="HttpRequestData"/> of the network call.</param>
         /// <returns>A task that represents the asynchronous operation.</returns>
+        /// <exception cref="ArgumentNullException">If <paramref name="requestData"/> is <see langword="null"/>.</exception>
         public override async Task ContinueRequestWithoutModification(HttpRequestData requestData)
         {
+            if (requestData is null)
+            {
+                throw new ArgumentNullException(nameof(requestData));
+            }
+
             await fetch.ContinueRequest(new ContinueRequestCommandSettings() { RequestId = requestData.RequestId }).ConfigureAwait(false);
         }
 
@@ -212,7 +244,7 @@ public override async Task ContinueRequestWithoutModification(HttpRequestData re
         /// <param name="userName">The user name with which to authenticate.</param>
         /// <param name="password">The password with which to authenticate.</param>
         /// <returns>A task that represents the asynchronous operation.</returns>
-        public override async Task ContinueWithAuth(string requestId, string userName, string password)
+        public override async Task ContinueWithAuth(string requestId, string? userName, string? password)
         {
             await fetch.ContinueWithAuth(new ContinueWithAuthCommandSettings()
             {
@@ -248,8 +280,14 @@ await fetch.ContinueWithAuth(new ContinueWithAuthCommandSettings()
         /// </summary>
         /// <param name="responseData">The <see cref="HttpResponseData"/> object to which to add the response body.</param>
         /// <returns>A task that represents the asynchronous operation.</returns>
+        /// <exception cref="ArgumentNullException">If <paramref name="responseData"/> is <see langword="null"/>.</exception>
         public override async Task AddResponseBody(HttpResponseData responseData)
         {
+            if (responseData is null)
+            {
+                throw new ArgumentNullException(nameof(responseData));
+            }
+
             // If the response is a redirect, retrieving the body will throw an error in CDP.
             if (responseData.StatusCode < 300 || responseData.StatusCode > 399)
             {
@@ -273,12 +311,18 @@ public override async Task AddResponseBody(HttpResponseData responseData)
         /// </summary>
         /// <param name="responseData">The <see cref="HttpResponseData"/> of the network response.</param>
         /// <returns>A task that represents the asynchronous operation.</returns>
+        /// <exception cref="ArgumentNullException">If <paramref name="responseData"/> is <see langword="null"/>.</exception>
         public override async Task ContinueResponseWithoutModification(HttpResponseData responseData)
         {
+            if (responseData is null)
+            {
+                throw new ArgumentNullException(nameof(responseData));
+            }
+
             await fetch.ContinueResponse(new ContinueResponseCommandSettings() { RequestId = responseData.RequestId }).ConfigureAwait(false);
         }
 
-        private void OnFetchAuthRequired(object sender, Fetch.AuthRequiredEventArgs e)
+        private void OnFetchAuthRequired(object? sender, Fetch.AuthRequiredEventArgs e)
         {
             AuthRequiredEventArgs wrapped = new AuthRequiredEventArgs
             (
@@ -289,7 +333,7 @@ private void OnFetchAuthRequired(object sender, Fetch.AuthRequiredEventArgs e)
             this.OnAuthRequired(wrapped);
         }
 
-        private void OnFetchRequestPaused(object sender, Fetch.RequestPausedEventArgs e)
+        private void OnFetchRequestPaused(object? sender, Fetch.RequestPausedEventArgs e)
         {
             if (e.ResponseErrorReason == null && e.ResponseStatusCode == null)
             {
diff --git a/dotnet/src/webdriver/DevTools/v85/V85Network.cs b/dotnet/src/webdriver/DevTools/v85/V85Network.cs
index f660049cf2548..8a2e38ff471a5 100644
--- a/dotnet/src/webdriver/DevTools/v85/V85Network.cs
+++ b/dotnet/src/webdriver/DevTools/v85/V85Network.cs
@@ -24,6 +24,8 @@
 using System.Text;
 using System.Threading.Tasks;
 
+#nullable enable
+
 namespace OpenQA.Selenium.DevTools.V85
 {
     /// <summary>
@@ -39,10 +41,11 @@ public class V85Network : DevTools.Network
         /// </summary>
         /// <param name="network">The adapter for the Network domain.</param>
         /// <param name="fetch">The adapter for the Fetch domain.</param>
+        /// <exception cref="ArgumentNullException">If <paramref name="network"/> or <paramref name="fetch"/> are <see langword="null"/>.</exception>
         public V85Network(NetworkAdapter network, FetchAdapter fetch)
         {
-            this.network = network;
-            this.fetch = fetch;
+            this.network = network ?? throw new ArgumentNullException(nameof(network));
+            this.fetch = fetch ?? throw new ArgumentNullException(nameof(fetch));
             fetch.AuthRequired += OnFetchAuthRequired;
             fetch.RequestPaused += OnFetchRequestPaused;
         }
@@ -66,7 +69,7 @@ public override async Task EnableNetworkCaching()
         }
 
         /// <summary>
-        /// Asynchronously ensables the Network domain..
+        /// Asynchronously enables the Network domain..
         /// </summary>
         /// <returns>A task that represents the asynchronous operation.</returns>
         public override async Task EnableNetwork()
@@ -101,7 +104,7 @@ await fetch.Enable(new Fetch.EnableCommandSettings()
         }
 
         /// <summary>
-        /// Asynchronously diables the fetch domain.
+        /// Asynchronously disables the fetch domain.
         /// </summary>
         /// <returns>A task that represents the asynchronous operation.</returns>
         public override async Task DisableFetch()
@@ -114,8 +117,14 @@ public override async Task DisableFetch()
         /// </summary>
         /// <param name="userAgent">A <see cref="UserAgent"/> object containing the user agent values to override.</param>
         /// <returns>A task that represents the asynchronous operation.</returns>
+        /// <exception cref="ArgumentNullException">If <paramref name="userAgent"/> is null.</exception>
         public override async Task SetUserAgentOverride(UserAgent userAgent)
         {
+            if (userAgent is null)
+            {
+                throw new ArgumentNullException(nameof(userAgent));
+            }
+
             await network.SetUserAgentOverride(new SetUserAgentOverrideCommandSettings()
             {
                 UserAgent = userAgent.UserAgentString,
@@ -129,8 +138,14 @@ await network.SetUserAgentOverride(new SetUserAgentOverrideCommandSettings()
         /// </summary>
         /// <param name="requestData">The <see cref="HttpRequestData"/> of the request.</param>
         /// <returns>A task that represents the asynchronous operation.</returns>
+        /// <exception cref="ArgumentNullException">If <paramref name="requestData"/> is <see langword="null"/>.</exception>
         public override async Task ContinueRequest(HttpRequestData requestData)
         {
+            if (requestData is null)
+            {
+                throw new ArgumentNullException(nameof(requestData));
+            }
+
             var commandSettings = new ContinueRequestCommandSettings()
             {
                 RequestId = requestData.RequestId,
@@ -163,8 +178,19 @@ public override async Task ContinueRequest(HttpRequestData requestData)
         /// <param name="requestData">The <see cref="HttpRequestData"/> of the request.</param>
         /// <param name="responseData">The <see cref="HttpResponseData"/> with which to respond to the request</param>
         /// <returns>A task that represents the asynchronous operation.</returns>
+        /// <exception cref="ArgumentNullException">If <paramref name="requestData"/> or <paramref name="responseData"/> are <see langword="null"/>.</exception>
         public override async Task ContinueRequestWithResponse(HttpRequestData requestData, HttpResponseData responseData)
         {
+            if (requestData is null)
+            {
+                throw new ArgumentNullException(nameof(requestData));
+            }
+
+            if (responseData is null)
+            {
+                throw new ArgumentNullException(nameof(responseData));
+            }
+
             var commandSettings = new FulfillRequestCommandSettings()
             {
                 RequestId = requestData.RequestId,
@@ -196,12 +222,18 @@ public override async Task ContinueRequestWithResponse(HttpRequestData requestDa
         }
 
         /// <summary>
-        /// Asynchronously contines an intercepted network call without modification.
+        /// Asynchronously continues an intercepted network call without modification.
         /// </summary>
         /// <param name="requestData">The <see cref="HttpRequestData"/> of the network call.</param>
         /// <returns>A task that represents the asynchronous operation.</returns>
+        /// <exception cref="ArgumentNullException">If <paramref name="requestData"/> is <see langword="null"/>.</exception>
         public override async Task ContinueRequestWithoutModification(HttpRequestData requestData)
         {
+            if (requestData is null)
+            {
+                throw new ArgumentNullException(nameof(requestData));
+            }
+
             await fetch.ContinueRequest(new ContinueRequestCommandSettings() { RequestId = requestData.RequestId }).ConfigureAwait(false);
         }
 
@@ -212,7 +244,7 @@ public override async Task ContinueRequestWithoutModification(HttpRequestData re
         /// <param name="userName">The user name with which to authenticate.</param>
         /// <param name="password">The password with which to authenticate.</param>
         /// <returns>A task that represents the asynchronous operation.</returns>
-        public override async Task ContinueWithAuth(string requestId, string userName, string password)
+        public override async Task ContinueWithAuth(string requestId, string? userName, string? password)
         {
             await fetch.ContinueWithAuth(new ContinueWithAuthCommandSettings()
             {
@@ -248,8 +280,14 @@ await fetch.ContinueWithAuth(new ContinueWithAuthCommandSettings()
         /// </summary>
         /// <param name="responseData">The <see cref="HttpResponseData"/> object to which to add the response body.</param>
         /// <returns>A task that represents the asynchronous operation.</returns>
+        /// <exception cref="ArgumentNullException">If <paramref name="responseData"/> is <see langword="null"/>.</exception>
         public override async Task AddResponseBody(HttpResponseData responseData)
         {
+            if (responseData is null)
+            {
+                throw new ArgumentNullException(nameof(responseData));
+            }
+
             // If the response is a redirect, retrieving the body will throw an error in CDP.
             if (responseData.StatusCode < 300 || responseData.StatusCode > 399)
             {
@@ -270,12 +308,18 @@ public override async Task AddResponseBody(HttpResponseData responseData)
         /// </summary>
         /// <param name="responseData">The <see cref="HttpResponseData"/> of the network response.</param>
         /// <returns>A task that represents the asynchronous operation.</returns>
+        /// <exception cref="ArgumentNullException">If <paramref name="responseData"/> is <see langword="null"/>.</exception>
         public override async Task ContinueResponseWithoutModification(HttpResponseData responseData)
         {
+            if (responseData is null)
+            {
+                throw new ArgumentNullException(nameof(responseData));
+            }
+
             await fetch.ContinueRequest(new ContinueRequestCommandSettings() { RequestId = responseData.RequestId }).ConfigureAwait(false);
         }
 
-        private void OnFetchAuthRequired(object sender, Fetch.AuthRequiredEventArgs e)
+        private void OnFetchAuthRequired(object? sender, Fetch.AuthRequiredEventArgs e)
         {
             AuthRequiredEventArgs wrapped = new AuthRequiredEventArgs
             (
@@ -286,7 +330,7 @@ private void OnFetchAuthRequired(object sender, Fetch.AuthRequiredEventArgs e)
             this.OnAuthRequired(wrapped);
         }
 
-        private void OnFetchRequestPaused(object sender, Fetch.RequestPausedEventArgs e)
+        private void OnFetchRequestPaused(object? sender, Fetch.RequestPausedEventArgs e)
         {
             if (e.ResponseErrorReason == null && e.ResponseStatusCode == null)
             {
diff --git a/dotnet/src/webdriver/ICredentials.cs b/dotnet/src/webdriver/ICredentials.cs
index 971c3dcb821e8..e56e6ea1b76de 100644
--- a/dotnet/src/webdriver/ICredentials.cs
+++ b/dotnet/src/webdriver/ICredentials.cs
@@ -17,6 +17,8 @@
 // under the License.
 // </copyright>
 
+#nullable enable
+
 namespace OpenQA.Selenium
 {
     /// <summary>
diff --git a/dotnet/src/webdriver/NetworkManager.cs b/dotnet/src/webdriver/NetworkManager.cs
index b508c32140ca0..eae9b433c7cbb 100644
--- a/dotnet/src/webdriver/NetworkManager.cs
+++ b/dotnet/src/webdriver/NetworkManager.cs
@@ -200,7 +200,7 @@ private async Task OnAuthRequired(object sender, AuthRequiredEventArgs e)
             {
                 if (authenticationHandler.UriMatcher.Invoke(uri))
                 {
-                    PasswordCredentials credentials = authenticationHandler.Credentials as PasswordCredentials;
+                    PasswordCredentials credentials = (PasswordCredentials)authenticationHandler.Credentials;
                     await this.session.Value.Domains.Network.ContinueWithAuth(e.RequestId, credentials.UserName, credentials.Password).ConfigureAwait(false);
                     successfullyAuthenticated = true;
                     break;
diff --git a/dotnet/src/webdriver/PasswordCredentials.cs b/dotnet/src/webdriver/PasswordCredentials.cs
index f22d40f0bb425..4709ead785517 100644
--- a/dotnet/src/webdriver/PasswordCredentials.cs
+++ b/dotnet/src/webdriver/PasswordCredentials.cs
@@ -17,6 +17,8 @@
 // under the License.
 // </copyright>
 
+#nullable enable
+
 namespace OpenQA.Selenium
 {
     /// <summary>
@@ -37,7 +39,7 @@ public PasswordCredentials()
         /// </summary>
         /// <param name="userName">The user name for the credentials.</param>
         /// <param name="password">The password for the credentials.</param>
-        public PasswordCredentials(string userName, string password)
+        public PasswordCredentials(string? userName, string? password)
         {
             UserName = userName;
             Password = password;
@@ -46,11 +48,11 @@ public PasswordCredentials(string userName, string password)
         /// <summary>
         /// Gets the user name.
         /// </summary>
-        public string UserName { get; private set; }
+        public string? UserName { get; }
 
         /// <summary>
         /// Gets the password.
         /// </summary>
-        public string Password { get; private set; }
+        public string? Password { get; }
     }
 }
diff --git a/dotnet/src/webdriver/UserAgent.cs b/dotnet/src/webdriver/UserAgent.cs
index 68b823b0a16a8..ba47a350b9291 100644
--- a/dotnet/src/webdriver/UserAgent.cs
+++ b/dotnet/src/webdriver/UserAgent.cs
@@ -17,6 +17,10 @@
 // under the License.
 // </copyright>
 
+#nullable enable
+
+using System;
+
 namespace OpenQA.Selenium.DevTools
 {
     /// <summary>
@@ -24,6 +28,24 @@ namespace OpenQA.Selenium.DevTools
     /// </summary>
     public class UserAgent
     {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="UserAgent"/> type.
+        /// </summary>
+        [Obsolete("Use the constructor which sets the userAgentString")]
+        public UserAgent()
+        {
+            UserAgentString = null!;
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="UserAgent"/> type.
+        /// </summary>
+        /// <param name="userAgentString">The user agent string.</param>
+        public UserAgent(string userAgentString)
+        {
+            UserAgentString = userAgentString;
+        }
+
         /// <summary>
         /// Gets or sets the user agent string.
         /// </summary>
@@ -32,11 +54,11 @@ public class UserAgent
         /// <summary>
         /// Gets or sets the language to accept in headers.
         /// </summary>
-        public string AcceptLanguage { get; set; }
+        public string? AcceptLanguage { get; set; }
 
         /// <summary>
         /// Gets or sets the value of the platform.
         /// </summary>
-        public string Platform { get; set; }
+        public string? Platform { get; set; }
     }
 }