[dotnet] Annotate nullability on interactions

dotnet/src/webdriver/ElementCoordinates.cs

@@ -21,47 +21,40 @@
 using OpenQA.Selenium.Internal;
 using System;
 
+#nullable enable
+
 namespace OpenQA.Selenium
 {
     /// <summary>
     /// Defines the interface through which the user can discover where an element is on the screen.
     /// </summary>
-    internal class ElementCoordinates : ICoordinates
+    internal sealed class ElementCoordinates : ICoordinates
     {
-        private WebElement element;
+        private readonly WebElement element;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="ElementCoordinates"/> class.
         /// </summary>
         /// <param name="element">The <see cref="WebElement"/> to be located.</param>
         public ElementCoordinates(WebElement element)
         {
-            this.element = element;
+            this.element = element ?? throw new ArgumentNullException(nameof(element));
         }
 
         /// <summary>
         /// Gets the location of an element in absolute screen coordinates.
         /// </summary>
-        public System.Drawing.Point LocationOnScreen
-        {
-            get { throw new NotImplementedException(); }
-        }
+        public System.Drawing.Point LocationOnScreen => throw new NotImplementedException();
 
         /// <summary>
         /// Gets the location of an element relative to the origin of the view port.
         /// </summary>
-        public System.Drawing.Point LocationInViewport
-        {
-            get { return this.element.LocationOnScreenOnceScrolledIntoView; }
-        }
+        public System.Drawing.Point LocationInViewport => this.element.LocationOnScreenOnceScrolledIntoView;
 
         /// <summary>
         /// Gets the location of an element's position within the HTML DOM.
         /// </summary>
-        public System.Drawing.Point LocationInDom
-        {
-            get { return this.element.Location; }
-        }
+        public System.Drawing.Point LocationInDom => this.element.Location;
 
         /// <summary>
         /// Gets a locator providing a user-defined location for this element.
@@ -70,17 +63,11 @@ public object AuxiliaryLocator
         {
             get
             {
-                IWebDriverObjectReference elementReference = this.element as IWebDriverObjectReference;
-                if (elementReference == null)
-                {
-                    return null;
-                }
-
                 // Note that the OSS dialect of the wire protocol for the Actions API
                 // uses the raw ID of the element, not an element reference. To use this,
                 // extract the ID using the well-known key to the dictionary for element
                 // references.
-                return elementReference.ObjectReferenceId;
+                return ((IWebDriverObjectReference)this.element).ObjectReferenceId;
             }
         }
     }

dotnet/src/webdriver/Interactions/ActionSequence.cs

@@ -22,14 +22,16 @@
 using System.Globalization;
 using System.Text;
 
+#nullable enable
+
 namespace OpenQA.Selenium.Interactions
 {
     /// <summary>
     /// Represents a sequence of actions to be performed in the target browser.
     /// </summary>
     public class ActionSequence
     {
-        private List<Interaction> interactions = new List<Interaction>();
+        private readonly List<Interaction> interactions = new List<Interaction>();
 
         /// <summary>
         /// Initializes a new instance of the <see cref="ActionSequence"/> class.
@@ -47,26 +49,18 @@ public ActionSequence(InputDevice device)
         /// <param name="initialSize">the initial size of the sequence.</param>
         public ActionSequence(InputDevice device, int initialSize)
         {
-            if (device == null)
-            {
-                throw new ArgumentNullException(nameof(device), "Input device cannot be null.");
-            }
-
-            this.InputDevice = device;
+            this.InputDevice = device ?? throw new ArgumentNullException(nameof(device), "Input device cannot be null.");
 
             for (int i = 0; i < initialSize; i++)
             {
-                this.AddAction(new PauseInteraction(device, TimeSpan.Zero));
+                this.AddAction(new PauseInteraction(this.InputDevice, TimeSpan.Zero));
             }
         }
 
         /// <summary>
         /// Gets the count of actions in the sequence.
         /// </summary>
-        public int Count
-        {
-            get { return this.interactions.Count; }
-        }
+        public int Count => this.interactions.Count;
 
         /// <summary>
         /// Gets the input device for this Action sequence.

dotnet/src/webdriver/Interactions/IAction.cs

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

dotnet/src/webdriver/Interactions/ICoordinates.cs

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

dotnet/src/webdriver/Interactions/InputDeviceKind.cs

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

dotnet/src/webdriver/Interactions/Interaction.cs

@@ -20,36 +20,28 @@
 using System;
 using System.Collections.Generic;
 
+#nullable enable
+
 namespace OpenQA.Selenium.Interactions
 {
     /// <summary>
     /// Represents a single interaction for a given input device.
     /// </summary>
     public abstract class Interaction
     {
-        private InputDevice sourceDevice;
-
         /// <summary>
         /// Initializes a new instance of the <see cref="Interaction"/> class.
         /// </summary>
         /// <param name="sourceDevice">The input device which performs this action.</param>
         protected Interaction(InputDevice sourceDevice)
         {
-            if (sourceDevice == null)
-            {
-                throw new ArgumentNullException(nameof(sourceDevice), "Source device cannot be null");
-            }
-
-            this.sourceDevice = sourceDevice;
+            this.SourceDevice = sourceDevice ?? throw new ArgumentNullException(nameof(sourceDevice), "Source device cannot be null");
         }
 
         /// <summary>
         /// Gets the device for which this action is intended.
         /// </summary>
-        public InputDevice SourceDevice
-        {
-            get { return this.sourceDevice; }
-        }
+        public InputDevice SourceDevice { get; }
 
         /// <summary>
         /// Returns a value for this action that can be transmitted across the wire to a remote end.
@@ -65,7 +57,7 @@ public InputDevice SourceDevice
         /// otherwise, <see langword="false"/>.</returns>
         public virtual bool IsValidFor(InputDeviceKind sourceDeviceKind)
         {
-            return this.sourceDevice.DeviceKind == sourceDeviceKind;
+            return this.SourceDevice.DeviceKind == sourceDeviceKind;
         }
     }
 }

dotnet/src/webdriver/Interactions/PauseInteraction.cs

@@ -21,14 +21,16 @@
 using System.Collections.Generic;
 using System.Globalization;
 
+#nullable enable
+
 namespace OpenQA.Selenium.Interactions
 {
     /// <summary>
     /// Represents a pause action.
     /// </summary>
     internal class PauseInteraction : Interaction
     {
-        private TimeSpan duration = TimeSpan.Zero;
+        private readonly TimeSpan duration = TimeSpan.Zero;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="PauseInteraction"/> class.

dotnet/src/webdriver/WebElement.cs

@@ -48,10 +48,11 @@ public class WebElement : IWebElement, IFindsElement, IWrapsDriver, ILocatable,
         /// </summary>
         /// <param name="parentDriver">The <see cref="WebDriver"/> instance that is driving this element.</param>
         /// <param name="id">The ID value provided to identify the element.</param>
+        /// <exception cref="ArgumentNullException">If <paramref name="id"/> is <see langword="null"/>.</exception>
         public WebElement(WebDriver parentDriver, string id)
         {
             this.driver = parentDriver;
-            this.elementId = id;
+            this.elementId = id ?? throw new ArgumentNullException(nameof(id));
         }
 
         /// <summary>