[dotnet] Annotate nullability on elements and WebDriver (SeleniumHQ#15352)

* [dotnet] Annotate nullability on elements and `WebDriver`

* Fix null warnings

Author: RenderMichael

dotnet/src/support/Events/EventFiringWebDriver.cs

@@ -442,14 +442,14 @@ public void Dispose()
         /// variable, as if the function were called via "Function.apply"
         /// </para>
         /// </remarks>
-        public object ExecuteScript(string script, params object?[] args)
+        public object? ExecuteScript(string script, params object?[] args)
         {
             if (this.WrappedDriver is not IJavaScriptExecutor javascriptDriver)
             {
                 throw new NotSupportedException("Underlying driver instance does not support executing JavaScript");
             }
 
-            object scriptResult;
+            object? scriptResult;
             try
             {
                 object?[] unwrappedArgs = UnwrapElementArguments(args);
@@ -505,7 +505,7 @@ public object ExecuteScript(string script, params object?[] args)
         /// variable, as if the function were called via "Function.apply"
         /// </para>
         /// </remarks>
-        public object ExecuteScript(PinnedScript script, params object?[] args)
+        public object? ExecuteScript(PinnedScript script, params object?[] args)
         {
             if (script == null)
             {
@@ -517,7 +517,7 @@ public object ExecuteScript(PinnedScript script, params object?[] args)
                 throw new NotSupportedException("Underlying driver instance does not support executing JavaScript");
             }
 
-            object scriptResult;
+            object? scriptResult;
             try
             {
                 object?[] unwrappedArgs = UnwrapElementArguments(args);
@@ -542,14 +542,14 @@ public object ExecuteScript(PinnedScript script, params object?[] args)
         /// <param name="script">The JavaScript code to execute.</param>
         /// <param name="args">The arguments to the script.</param>
         /// <returns>The value returned by the script.</returns>
-        public object ExecuteAsyncScript(string script, params object?[] args)
+        public object? ExecuteAsyncScript(string script, params object?[] args)
         {
             if (this.WrappedDriver is not IJavaScriptExecutor javascriptDriver)
             {
                 throw new NotSupportedException("Underlying driver instance does not support executing JavaScript");
             }
 
-            object scriptResult;
+            object? scriptResult;
             try
             {
                 object?[] unwrappedArgs = UnwrapElementArguments(args);
@@ -1589,20 +1589,17 @@ public void Click()
             /// </summary>
             /// <param name="attributeName">Attribute you wish to get details of</param>
             /// <returns>The attribute's current value or null if the value is not set.</returns>
-            public string GetAttribute(string attributeName)
+            public string? GetAttribute(string attributeName)
             {
-                string attribute;
                 try
                 {
-                    attribute = this.WrappedElement.GetAttribute(attributeName);
+                    return this.WrappedElement.GetAttribute(attributeName);
                 }
                 catch (Exception ex)
                 {
                     this.parentDriver.OnException(new WebDriverExceptionEventArgs(this.parentDriver, ex));
                     throw;
                 }
-
-                return attribute;
             }
 
             /// <summary>
@@ -1617,20 +1614,17 @@ public string GetAttribute(string attributeName)
             /// of an IDL property of the element, either use the <see cref="GetAttribute(string)"/>
             /// method or the <see cref="GetDomProperty(string)"/> method.
             /// </remarks>
-            public string GetDomAttribute(string attributeName)
+            public string? GetDomAttribute(string attributeName)
             {
-                string attribute;
                 try
                 {
-                    attribute = this.WrappedElement.GetDomAttribute(attributeName);
+                    return this.WrappedElement.GetDomAttribute(attributeName);
                 }
                 catch (Exception ex)
                 {
                     this.parentDriver.OnException(new WebDriverExceptionEventArgs(this.parentDriver, ex));
                     throw;
                 }
-
-                return attribute;
             }
 
             /// <summary>
@@ -1639,20 +1633,17 @@ public string GetDomAttribute(string attributeName)
             /// <param name="propertyName">The name of the JavaScript property to get the value of.</param>
             /// <returns>The JavaScript property's current value. Returns a <see langword="null"/> if the
             /// value is not set or the property does not exist.</returns>
-            public string GetDomProperty(string propertyName)
+            public string? GetDomProperty(string propertyName)
             {
-                string elementProperty;
                 try
                 {
-                    elementProperty = this.WrappedElement.GetDomProperty(propertyName);
+                    return this.WrappedElement.GetDomProperty(propertyName);
                 }
                 catch (Exception ex)
                 {
                     this.parentDriver.OnException(new WebDriverExceptionEventArgs(this.parentDriver, ex));
                     throw;
                 }
-
-                return elementProperty;
             }
 
             /// <summary>
@@ -1683,22 +1674,19 @@ public string GetCssValue(string propertyName)
             /// <returns>A shadow root representation.</returns>
             public ISearchContext GetShadowRoot()
             {
-                ISearchContext shadowRoot;
                 try
                 {
                     GetShadowRootEventArgs e = new GetShadowRootEventArgs(this.parentDriver.WrappedDriver, this.WrappedElement);
                     this.parentDriver.OnGettingShadowRoot(e);
-                    shadowRoot = this.WrappedElement.GetShadowRoot();
+                    ISearchContext shadowRoot = this.WrappedElement.GetShadowRoot();
                     this.parentDriver.OnGetShadowRootCompleted(e);
-                    shadowRoot = new EventFiringShadowRoot(this.parentDriver, shadowRoot);
+                    return new EventFiringShadowRoot(this.parentDriver, shadowRoot);
                 }
                 catch (Exception ex)
                 {
                     this.parentDriver.OnException(new WebDriverExceptionEventArgs(this.parentDriver, ex));
                     throw;
                 }
-
-                return shadowRoot;
             }
 
             /// <summary>

dotnet/src/webdriver/By.cs

@@ -99,7 +99,7 @@ protected By(Func<ISearchContext, IWebElement> findElementMethod, Func<ISearchCo
         protected string Description { get; set; } = "OpenQA.Selenium.By";
 
         /// <summary>
-        /// Gets or sets the method used to find a single element matching specified criteria.
+        /// Gets or sets the method used to find a single element matching specified criteria, or throws <see cref="NoSuchElementException"/> if no element is found.
         /// </summary>
         protected Func<ISearchContext, IWebElement>? FindElementMethod { get; set; }
 
@@ -324,6 +324,7 @@ public static By CssSelector(string cssSelectorToFind)
         /// </summary>
         /// <param name="context">An <see cref="ISearchContext"/> object to use to search for the elements.</param>
         /// <returns>The first matching <see cref="IWebElement"/> on the current context.</returns>
+        /// <exception cref="NoSuchElementException">If no element matches the criteria.</exception>
         public virtual IWebElement FindElement(ISearchContext context)
         {
             if (this.FindElementMethod is not { } findElementMethod)

dotnet/src/webdriver/Chromium/ChromiumDriver.cs

@@ -168,7 +168,7 @@ private static ICommandExecutor GenerateDriverServiceCommandExecutor(DriverServi
                 string fullServicePath = finder.GetDriverPath();
                 service.DriverServicePath = Path.GetDirectoryName(fullServicePath);
                 service.DriverServiceExecutableName = Path.GetFileName(fullServicePath);
-                if (finder.TryGetBrowserPath(out string browserPath))
+                if (finder.TryGetBrowserPath(out string? browserPath))
                 {
                     options.BinaryLocation = browserPath;
                     options.BrowserVersion = null;

dotnet/src/webdriver/Command.cs

@@ -56,10 +56,10 @@ public Command(string name, string jsonParameters)
         /// <param name="name">Name of the command</param>
         /// <param name="parameters">Parameters for that command</param>
         /// <exception cref="ArgumentNullException">If <paramref name="name"/> is <see langword="null"/>.</exception>
-        public Command(SessionId? sessionId, string name, Dictionary<string, object>? parameters)
+        public Command(SessionId? sessionId, string name, Dictionary<string, object?>? parameters)
         {
             this.SessionId = sessionId;
-            this.Parameters = parameters ?? new Dictionary<string, object>();
+            this.Parameters = parameters ?? new Dictionary<string, object?>();
             this.Name = name ?? throw new ArgumentNullException(nameof(name));
         }
 
@@ -79,7 +79,7 @@ public Command(SessionId? sessionId, string name, Dictionary<string, object>? pa
         /// Gets the parameters of the command
         /// </summary>
         [JsonPropertyName("parameters")]
-        public Dictionary<string, object> Parameters { get; }
+        public Dictionary<string, object?> Parameters { get; }
 
         /// <summary>
         /// Gets the parameters of the command as a JSON-encoded string.
@@ -118,9 +118,9 @@ public override string ToString()
         /// <returns>A <see cref="Dictionary{K, V}"/> with a string keys, and an object value. </returns>
         /// <exception cref="JsonException">If <paramref name="value"/> is not a JSON object.</exception>
         /// <exception cref="ArgumentNullException">If <paramref name="value"/> is <see langword="null"/>.</exception>
-        private static Dictionary<string, object>? ConvertParametersFromJson(string value)
+        private static Dictionary<string, object?>? ConvertParametersFromJson(string value)
         {
-            Dictionary<string, object>? parameters = JsonSerializer.Deserialize<Dictionary<string, object>>(value, s_jsonSerializerOptions);
+            Dictionary<string, object?>? parameters = JsonSerializer.Deserialize<Dictionary<string, object?>>(value, s_jsonSerializerOptions);
             return parameters;
         }
     }

dotnet/src/webdriver/CookieJar.cs

@@ -127,7 +127,7 @@ public void DeleteAllCookies()
             {
                 var rawCookie = driver.InternalExecute(DriverCommand.GetCookie, new() { { "name", name } }).Value;
 
-                return Cookie.FromDictionary((Dictionary<string, object>)rawCookie!);
+                return Cookie.FromDictionary((Dictionary<string, object?>)rawCookie!);
             }
             catch (NoSuchCookieException)
             {

dotnet/src/webdriver/Firefox/FirefoxDriver.cs

@@ -221,7 +221,7 @@ private static ICommandExecutor GenerateDriverServiceCommandExecutor(DriverServi
                 string fullServicePath = finder.GetDriverPath();
                 service.DriverServicePath = Path.GetDirectoryName(fullServicePath);
                 service.DriverServiceExecutableName = Path.GetFileName(fullServicePath);
-                if (finder.TryGetBrowserPath(out string browserPath))
+                if (finder.TryGetBrowserPath(out string? browserPath))
                 {
                     options.BinaryLocation = browserPath;
                     options.BrowserVersion = null;

dotnet/src/webdriver/Firefox/FirefoxProfile.cs

@@ -160,7 +160,7 @@ public void WriteToDisk()
             this.ProfileDirectory = GenerateProfileDirectoryName();
             if (!string.IsNullOrEmpty(this.sourceProfileDir))
             {
-                FileUtilities.CopyDirectory(this.sourceProfileDir, this.ProfileDirectory);
+                FileUtilities.CopyDirectory(this.sourceProfileDir!, this.ProfileDirectory);
             }
             else
             {

dotnet/src/webdriver/IJavascriptExecutor.cs

@@ -20,6 +20,8 @@
 using System;
 using System.Collections.Generic;
 
+#nullable enable
+
 namespace OpenQA.Selenium
 {
     /// <summary>
@@ -62,7 +64,7 @@ public interface IJavaScriptExecutor
         /// variable, as if the function were called via "Function.apply"
         /// </para>
         /// </remarks>
-        object ExecuteScript(string script, params object[] args);
+        object? ExecuteScript(string script, params object?[] args);
 
         /// <summary>
         /// Executes JavaScript in the context of the currently selected frame or window.
@@ -100,14 +102,14 @@ public interface IJavaScriptExecutor
         /// </para>
         /// </remarks>
         /// <exception cref="ArgumentNullException">If <paramref name="script" /> is <see langword="null"/>.</exception>
-        object ExecuteScript(PinnedScript script, params object[] args);
+        object? ExecuteScript(PinnedScript script, params object?[] args);
 
         /// <summary>
         /// Executes JavaScript asynchronously in the context of the currently selected frame or window.
         /// </summary>
         /// <param name="script">The JavaScript code to execute.</param>
         /// <param name="args">The arguments to the script.</param>
         /// <returns>The value returned by the script.</returns>
-        object ExecuteAsyncScript(string script, params object[] args);
+        object? ExecuteAsyncScript(string script, params object?[] args);
     }
 }

dotnet/src/webdriver/IWebDriver.cs

@@ -20,6 +20,8 @@
 using System;
 using System.Collections.ObjectModel;
 
+#nullable enable
+
 namespace OpenQA.Selenium
 {
     /// <summary>

dotnet/src/webdriver/IWebElement.cs

@@ -20,6 +20,8 @@
 using System;
 using System.Drawing;
 
+#nullable enable
+
 namespace OpenQA.Selenium
 {
     /// <summary>
@@ -170,7 +172,7 @@ public interface IWebElement : ISearchContext
         /// </list>
         /// </remarks>
         /// <exception cref="StaleElementReferenceException">Thrown when the target element is no longer valid in the document DOM.</exception>
-        string GetAttribute(string attributeName);
+        string? GetAttribute(string attributeName);
 
         /// <summary>
         /// Gets the value of a declared HTML attribute of this element.
@@ -185,7 +187,7 @@ public interface IWebElement : ISearchContext
         /// of an IDL property of the element, either use the <see cref="GetAttribute(string)"/>
         /// method or the <see cref="GetDomProperty(string)"/> method.
         /// </remarks>
-        string GetDomAttribute(string attributeName);
+        string? GetDomAttribute(string attributeName);
 
         /// <summary>
         /// Gets the value of a JavaScript property of this element.
@@ -194,7 +196,7 @@ public interface IWebElement : ISearchContext
         /// <returns>The JavaScript property's current value. Returns a <see langword="null"/> if the
         /// value is not set or the property does not exist.</returns>
         /// <exception cref="StaleElementReferenceException">Thrown when the target element is no longer valid in the document DOM.</exception>
-        string GetDomProperty(string propertyName);
+        string? GetDomProperty(string propertyName);
 
         /// <summary>
         /// Gets the value of a CSS property of this element.

dotnet/src/webdriver/RelativeBy.cs

@@ -108,7 +108,7 @@ public override ReadOnlyCollection<IWebElement> FindElements(ISearchContext cont
             filterParameters["root"] = GetSerializableObject(this.root);
             filterParameters["filters"] = this.filters;
             parameters["relative"] = filterParameters;
-            object rawElements = js.ExecuteScript(wrappedAtom, parameters);
+            object? rawElements = js.ExecuteScript(wrappedAtom, parameters);
 
             if (rawElements is ReadOnlyCollection<IWebElement> elements)
             {

dotnet/src/webdriver/ShadowRoot.cs

@@ -99,7 +99,7 @@ public IWebElement FindElement(By by)
             parameters.Add("value", by.Criteria);
 
             Response commandResponse = this.driver.InternalExecute(DriverCommand.FindShadowChildElement, parameters);
-            return this.driver.GetElementFromResponse(commandResponse);
+            return this.driver.GetElementFromResponse(commandResponse)!;
         }
 
         /// <summary>

dotnet/src/webdriver/TargetLocator.cs

@@ -166,7 +166,7 @@ public IWebDriver Window(string windowHandleOrName)
                 foreach (string handle in this.driver.WindowHandles)
                 {
                     this.Window(handle);
-                    if (windowHandleOrName == this.driver.ExecuteScript("return window.name").ToString())
+                    if (windowHandleOrName == this.driver.ExecuteScript("return window.name")!.ToString())
                     {
                         return this.driver; // found by name
                     }
@@ -223,7 +223,7 @@ public IWebDriver DefaultContent()
         public IWebElement ActiveElement()
         {
             Response response = this.driver.InternalExecute(DriverCommand.GetActiveElement, null);
-            return this.driver.GetElementFromResponse(response);
+            return this.driver.GetElementFromResponse(response)!;
         }
 
         /// <summary>

dotnet/src/webdriver/WebDriver.cs

@@ -28,6 +28,8 @@
 using System.Globalization;
 using System.Threading.Tasks;
 
+#nullable enable
+
 namespace OpenQA.Selenium
 {
     /// <summary>
@@ -40,10 +42,10 @@ public class WebDriver : IWebDriver, ISearchContext, IJavaScriptExecutor, IFinds
         /// </summary>
         protected static readonly TimeSpan DefaultCommandTimeout = TimeSpan.FromSeconds(60);
         private IFileDetector fileDetector = new DefaultFileDetector();
-        private NetworkManager network;
+        private readonly NetworkManager network;
         private WebElementFactory elementFactory;
 
-        private List<string> registeredCommands = new List<string>();
+        private readonly List<string> registeredCommands = new List<string>();
 
         /// <summary>
         /// Initializes a new instance of the <see cref="WebDriver"/> class.
@@ -108,7 +110,7 @@ public string Url
                 Response commandResponse = this.Execute(DriverCommand.GetCurrentUrl, null);
 
                 commandResponse.EnsureValueIsNotNull();
-                return commandResponse.Value.ToString();
+                return commandResponse.Value.ToString()!;
             }
 
             set => new Navigator(this).GoToUrl(value);
@@ -122,13 +124,11 @@ public string Title
             get
             {
                 Response commandResponse = this.Execute(DriverCommand.GetTitle, null);
-                object returnedTitle = commandResponse.Value ?? string.Empty;
 
-                return returnedTitle.ToString();
+                return commandResponse.Value?.ToString() ?? string.Empty;
             }
         }
 
-
         /// <summary>
         /// Gets the source of the page last loaded by the browser.
         /// </summary>
@@ -139,7 +139,7 @@ public string PageSource
                 Response commandResponse = this.Execute(DriverCommand.GetPageSource, null);
 
                 commandResponse.EnsureValueIsNotNull();
-                return commandResponse.Value.ToString();
+                return commandResponse.Value.ToString()!;
             }
         }
 
@@ -154,7 +154,7 @@ public string CurrentWindowHandle
                 Response commandResponse = this.Execute(DriverCommand.GetCurrentWindowHandle, null);
 
                 commandResponse.EnsureValueIsNotNull();
-                return commandResponse.Value.ToString();
+                return commandResponse.Value.ToString()!;
             }
         }
 
@@ -168,11 +168,11 @@ public ReadOnlyCollection<string> WindowHandles
                 Response commandResponse = this.Execute(DriverCommand.GetWindowHandles, null);
 
                 commandResponse.EnsureValueIsNotNull();
-                object[] handles = (object[])commandResponse.Value;
+                object?[] handles = (object?[])commandResponse.Value;
                 List<string> handleList = new List<string>(handles.Length);
-                foreach (object handle in handles)
+                foreach (object? handle in handles)
                 {
-                    handleList.Add(handle.ToString());
+                    handleList.Add(handle!.ToString()!);
                 }
 
                 return handleList.AsReadOnly();
@@ -184,8 +184,6 @@ public ReadOnlyCollection<string> WindowHandles
         /// </summary>
         public bool IsActionExecutor => true;
 
-#nullable enable
-
         /// <summary>
         /// Gets the <see cref="Selenium.SessionId"/> for the current session of this driver.
         /// </summary>
@@ -272,8 +270,6 @@ public void Dispose()
             return this.ExecuteScript(script.MakeExecutionScript(), args);
         }
 
-#nullable restore
-
         /// <summary>
         /// Finds the first element in the page that matches the <see cref="By"/> object
         /// </summary>
@@ -310,7 +306,7 @@ public virtual IWebElement FindElement(string mechanism, string value)
 
             Response commandResponse = this.Execute(DriverCommand.FindElement, parameters);
 
-            return this.GetElementFromResponse(commandResponse);
+            return this.GetElementFromResponse(commandResponse)!;
         }
 
         /// <summary>
@@ -351,8 +347,6 @@ public virtual ReadOnlyCollection<IWebElement> FindElements(string mechanism, st
             return this.GetElementsFromResponse(commandResponse);
         }
 
-#nullable enable
-
         /// <summary>
         /// Gets a <see cref="Screenshot"/> object representing the image of the page on the screen.
         /// </summary>
@@ -527,14 +521,8 @@ internal bool RegisterDriverCommand(string commandName, [NotNullWhen(true)] Comm
         /// </summary>
         /// <param name="response">Response from the browser</param>
         /// <returns>Element from the page, or <see langword="null"/> if the response does not contain a dictionary.</returns>
-        /// <exception cref="ArgumentNullException">If <paramref name="response"/> is <see langword="null"/>.</exception>
         internal IWebElement? GetElementFromResponse(Response response)
         {
-            if (response == null)
-            {
-                throw new NoSuchElementException();
-            }
-
             if (response.Value is Dictionary<string, object?> elementDictionary)
             {
                 return this.elementFactory.CreateElement(elementDictionary);
@@ -566,16 +554,18 @@ internal ReadOnlyCollection<IWebElement> GetElementsFromResponse(Response respon
             return toReturn.AsReadOnly();
         }
 
-#nullable restore
-
         /// <summary>
         /// Executes commands with the driver
         /// </summary>
         /// <param name="driverCommandToExecute">Command that needs executing</param>
         /// <param name="parameters">Parameters needed for the command</param>
         /// <returns>WebDriver Response</returns>
         /// <exception cref="ArgumentNullException">If <paramref name="driverCommandToExecute"/> is <see langword="null"/>.</exception>
-        internal Response InternalExecute(string driverCommandToExecute, Dictionary<string, object> parameters)
+        internal Response InternalExecute(string driverCommandToExecute, Dictionary<string,
+#nullable disable
+            object
+#nullable enable
+            >? parameters)
         {
             return Task.Run(() => this.InternalExecuteAsync(driverCommandToExecute, parameters)).GetAwaiter().GetResult();
         }
@@ -587,8 +577,11 @@ internal Response InternalExecute(string driverCommandToExecute, Dictionary<stri
         /// <param name="parameters">Parameters needed for the command</param>
         /// <returns>A task object representing the asynchronous operation</returns>
         /// <exception cref="ArgumentNullException">If <paramref name="driverCommandToExecute"/> is <see langword="null"/>.</exception>
-        internal Task<Response> InternalExecuteAsync(string driverCommandToExecute,
-            Dictionary<string, object> parameters)
+        internal Task<Response> InternalExecuteAsync(string driverCommandToExecute, Dictionary<string,
+#nullable disable
+                object
+#nullable enable
+                >? parameters)
         {
             return this.ExecuteAsync(driverCommandToExecute, parameters);
         }
@@ -600,8 +593,11 @@ internal Task<Response> InternalExecuteAsync(string driverCommandToExecute,
         /// <param name="parameters">A <see cref="Dictionary{K, V}"/> containing the names and values of the parameters of the command.</param>
         /// <returns>A <see cref="Response"/> containing information about the success or failure of the command and any data returned by the command.</returns>
         /// <exception cref="ArgumentNullException">If <paramref name="driverCommandToExecute"/> is <see langword="null"/>.</exception>
-        protected virtual Response Execute(string driverCommandToExecute,
-            Dictionary<string, object> parameters)
+        protected virtual Response Execute(string driverCommandToExecute, Dictionary<string,
+#nullable disable
+            object
+#nullable enable
+            >? parameters)
         {
             return Task.Run(() => this.ExecuteAsync(driverCommandToExecute, parameters)).GetAwaiter().GetResult();
         }
@@ -613,7 +609,11 @@ protected virtual Response Execute(string driverCommandToExecute,
         /// <param name="parameters">A <see cref="Dictionary{K, V}"/> containing the names and values of the parameters of the command.</param>
         /// <returns>A <see cref="Response"/> containing information about the success or failure of the command and any data returned by the command.</returns>
         /// <exception cref="ArgumentNullException">If <paramref name="driverCommandToExecute"/> is <see langword="null"/>.</exception>
-        protected virtual async Task<Response> ExecuteAsync(string driverCommandToExecute, Dictionary<string, object> parameters)
+        protected virtual async Task<Response> ExecuteAsync(string driverCommandToExecute, Dictionary<string,
+#nullable disable
+            object
+#nullable enable
+            >? parameters)
         {
             Command commandToExecute = new Command(SessionId, driverCommandToExecute, parameters);
 
@@ -702,8 +702,6 @@ protected virtual Dictionary<string, object> GetCapabilitiesDictionary(ICapabili
             return capabilitiesDictionary;
         }
 
-#nullable enable
-
         /// <summary>
         /// Registers a command to be executed with this driver instance as an internally known driver command.
         /// </summary>

dotnet/src/webdriver/WebElement.cs

@@ -28,6 +28,8 @@
 using System.IO.Compression;
 using System.Linq;
 
+#nullable enable
+
 namespace OpenQA.Selenium
 {
     /// <summary>
@@ -40,8 +42,6 @@ public class WebElement : IWebElement, IFindsElement, IWrapsDriver, ILocatable,
         /// </summary>
         public const string ElementReferencePropertyName = "element-6066-11e4-a52e-4f735466cecf";
 
-#nullable enable
-
         private readonly WebDriver driver;
 
         /// <summary>
@@ -327,8 +327,6 @@ public virtual void Click()
             this.Execute(DriverCommand.ClickElement, parameters);
         }
 
-#nullable restore
-
         /// <summary>
         /// Finds the first <see cref="IWebElement"/> using the given method.
         /// </summary>
@@ -346,8 +344,6 @@ public virtual IWebElement FindElement(By by)
             return by.FindElement(this);
         }
 
-#nullable enable
-
         /// <summary>
         /// Finds a child element matching the given mechanism and value.
         /// </summary>
@@ -363,11 +359,9 @@ public virtual IWebElement FindElement(string mechanism, string value)
 
             Response commandResponse = this.Execute(DriverCommand.FindChildElement, parameters);
 
-            return this.driver.GetElementFromResponse(commandResponse);
+            return this.driver.GetElementFromResponse(commandResponse)!;
         }
 
-#nullable restore
-
         /// <summary>
         /// Finds all <see cref="IWebElement">IWebElements</see> within the current context
         /// using the given mechanism.
@@ -385,8 +379,6 @@ public virtual ReadOnlyCollection<IWebElement> FindElements(By by)
             return by.FindElements(this);
         }
 
-#nullable enable
-
         /// <summary>
         /// Finds all child elements matching the given mechanism and value.
         /// </summary>
@@ -701,24 +693,24 @@ Dictionary<string, object> IWebDriverObjectReference.ToDictionary()
             return elementDictionary;
         }
 
-#nullable restore
-
         /// <summary>
         /// Executes a command on this element using the specified parameters.
         /// </summary>
         /// <param name="commandToExecute">The <see cref="DriverCommand"/> to execute against this element.</param>
         /// <param name="parameters">A <see cref="Dictionary{K, V}"/> containing names and values of the parameters for the command.</param>
         /// <returns>The <see cref="Response"/> object containing the result of the command execution.</returns>
-        protected virtual Response Execute(string commandToExecute, Dictionary<string, object> parameters)
+        protected virtual Response Execute(string commandToExecute, Dictionary<string,
+#nullable disable
+            object
+#nullable enable
+                >? parameters)
         {
             return this.driver.InternalExecute(commandToExecute, parameters);
         }
 
-#nullable enable
-
         private static string GetAtom(string atomResourceName)
         {
-            string atom = string.Empty;
+            string atom;
             using (Stream atomStream = ResourceUtilities.GetResourceStream(atomResourceName, atomResourceName))
             {
                 using (StreamReader atomReader = new StreamReader(atomStream))

dotnet/src/webdriver/WebElementFactory.cs

@@ -49,6 +49,9 @@ public WebElementFactory(WebDriver parentDriver)
         /// </summary>
         /// <param name="elementDictionary">The dictionary containing the element reference.</param>
         /// <returns>A <see cref="WebElement"/> containing the information from the specified dictionary.</returns>
+        /// <exception cref="ArgumentNullException">If <paramref name="elementDictionary"/> is <see langword="null"/>.</exception>
+        /// <exception cref="ArgumentException">If the dictionary does not contain the element reference property name.</exception>
+        /// <exception cref="InvalidOperationException">If the element property is <see langword="null"/> or <see cref="string.Empty"/>.</exception>
         public virtual WebElement CreateElement(Dictionary<string, object?> elementDictionary)
         {
             string elementId = this.GetElementId(elementDictionary);