revert a bunch of changes

dotnet/src/webdriver/INetwork.cs

@@ -20,8 +20,6 @@
 using System;
 using System.Threading.Tasks;
 
-#nullable enable
-
 namespace OpenQA.Selenium
 {
     /// <summary>
@@ -32,19 +30,18 @@ public interface INetwork
         /// <summary>
         /// Occurs when a browser sends a network request.
         /// </summary>
-        event EventHandler<NetworkRequestSentEventArgs>? NetworkRequestSent;
+        event EventHandler<NetworkRequestSentEventArgs> NetworkRequestSent;
 
         /// <summary>
         /// Occurs when a browser receives a network response.
         /// </summary>
-        event EventHandler<NetworkResponseReceivedEventArgs>? NetworkResponseReceived;
+        event EventHandler<NetworkResponseReceivedEventArgs> NetworkResponseReceived;
 
         /// <summary>
         /// Adds a <see cref="NetworkRequestHandler"/> to examine incoming network requests,
         /// and optionally modify the request or provide a response.
         /// </summary>
         /// <param name="handler">The <see cref="NetworkRequestHandler"/> to add.</param>
-        /// <exception cref="ArgumentNullException">If <paramref name="handler"/> is <see langword="null"/>.</exception>
         void AddRequestHandler(NetworkRequestHandler handler);
 
         /// <summary>

dotnet/src/webdriver/IOptions.cs

@@ -17,8 +17,6 @@
 // under the License.
 // </copyright>
 
-#nullable enable
-
 namespace OpenQA.Selenium
 {
     /// <summary>

dotnet/src/webdriver/ITimeouts.cs

@@ -19,8 +19,6 @@
 
 using System;
 
-#nullable enable
-
 namespace OpenQA.Selenium
 {
     /// <summary>

dotnet/src/webdriver/IWindow.cs

@@ -19,8 +19,6 @@
 
 using System.Drawing;
 
-#nullable enable
-
 namespace OpenQA.Selenium
 {
     /// <summary>

dotnet/src/webdriver/NetworkManager.cs

@@ -22,8 +22,6 @@
 using System.Collections.Generic;
 using System.Threading.Tasks;
 
-#nullable enable
-
 namespace OpenQA.Selenium
 {
     /// <summary>
@@ -47,7 +45,7 @@ public NetworkManager(IWebDriver driver)
             // StartMonitoring().
             this.session = new Lazy<DevToolsSession>(() =>
             {
-                IDevTools? devToolsDriver = driver as IDevTools;
+                IDevTools devToolsDriver = driver as IDevTools;
                 if (devToolsDriver == null)
                 {
                     throw new WebDriverException("Driver must implement IDevTools to use these features");
@@ -60,12 +58,12 @@ public NetworkManager(IWebDriver driver)
         /// <summary>
         /// Occurs when a browser sends a network request.
         /// </summary>
-        public event EventHandler<NetworkRequestSentEventArgs>? NetworkRequestSent;
+        public event EventHandler<NetworkRequestSentEventArgs> NetworkRequestSent;
 
         /// <summary>
         /// Occurs when a browser receives a network response.
         /// </summary>
-        public event EventHandler<NetworkResponseReceivedEventArgs>? NetworkResponseReceived;
+        public event EventHandler<NetworkResponseReceivedEventArgs> NetworkResponseReceived;
 
         /// <summary>
         /// Asynchronously starts monitoring for network traffic.
@@ -98,7 +96,6 @@ public async Task StopMonitoring()
         /// and optionally modify the request or provide a response.
         /// </summary>
         /// <param name="handler">The <see cref="NetworkRequestHandler"/> to add.</param>
-        /// <exception cref="ArgumentNullException">If <paramref name="handler"/> is null.</exception>
         public void AddRequestHandler(NetworkRequestHandler handler)
         {
             if (handler == null)
@@ -203,7 +200,7 @@ private async Task OnAuthRequired(object sender, AuthRequiredEventArgs e)
             {
                 if (authenticationHandler.UriMatcher.Invoke(uri))
                 {
-                    PasswordCredentials credentials = (PasswordCredentials)authenticationHandler.Credentials;
+                    PasswordCredentials credentials = authenticationHandler.Credentials as PasswordCredentials;
                     await this.session.Value.Domains.Network.ContinueWithAuth(e.RequestId, credentials.UserName, credentials.Password).ConfigureAwait(false);
                     successfullyAuthenticated = true;
                     break;

dotnet/src/webdriver/OptionsManager.cs

@@ -17,8 +17,6 @@
 // under the License.
 // </copyright>
 
-#nullable enable
-
 namespace OpenQA.Selenium
 {
     /// <summary>

dotnet/src/webdriver/Timeouts.cs

@@ -21,8 +21,6 @@
 using System.Collections.Generic;
 using System.Globalization;
 
-#nullable enable
-
 namespace OpenQA.Selenium
 {
     /// <summary>

dotnet/src/webdriver/Window.cs

@@ -22,8 +22,6 @@
 using System.Drawing;
 using System.Globalization;
 
-#nullable enable
-
 namespace OpenQA.Selenium
 {
     /// <summary>
@@ -98,7 +96,7 @@ public Size Size
         /// </summary>
         public void Maximize()
         {
-            Dictionary<string, object>? parameters = null;
+            Dictionary<string, object> parameters = null;
             this.driver.InternalExecute(DriverCommand.MaximizeWindow, parameters);
         }
 
@@ -107,7 +105,7 @@ public void Maximize()
         /// </summary>
         public void Minimize()
         {
-            Dictionary<string, object>? parameters = null;
+            Dictionary<string, object> parameters = null;
             this.driver.InternalExecute(DriverCommand.MinimizeWindow, parameters);
         }
 
@@ -116,7 +114,7 @@ public void Minimize()
         /// </summary>
         public void FullScreen()
         {
-            Dictionary<string, object>? parameters = null;
+            Dictionary<string, object> parameters = null;
             this.driver.InternalExecute(DriverCommand.FullScreenWindow, parameters);
         }
     }