[dotnet] Add nullability to IniFileReader (#14929)

Author: RenderMichael

dotnet/src/webdriver/Firefox/Internal/IniFileReader.cs

@@ -22,19 +22,23 @@
 using System.Collections.ObjectModel;
 using System.IO;
 
+#nullable enable
+
 namespace OpenQA.Selenium.Firefox.Internal
 {
     /// <summary>
     /// Parses and reads an INI file.
     /// </summary>
-    internal class IniFileReader
+    internal sealed class IniFileReader
     {
-        private Dictionary<string, Dictionary<string, string>> iniFileStore = new Dictionary<string, Dictionary<string, string>>();
+        private readonly Dictionary<string, Dictionary<string, string>> iniFileStore = new Dictionary<string, Dictionary<string, string>>();
 
         /// <summary>
         /// Initializes a new instance of the <see cref="IniFileReader"/> class.
         /// </summary>
         /// <param name="fileName">The full path to the .INI file to be read.</param>
+        /// <exception cref="ArgumentNullException">If <paramref name="fileName"/> is <see langword="null"/> or <see cref="string.Empty"/>.</exception>
+        /// <exception cref="FileNotFoundException">If no file exists at file path <paramref name="fileName"/>.</exception>
         public IniFileReader(string fileName)
         {
             if (string.IsNullOrEmpty(fileName))
@@ -53,7 +57,7 @@ public IniFileReader(string fileName)
             string[] iniFileContent = File.ReadAllLines(fileName);
             foreach (string iniFileLine in iniFileContent)
             {
-                if (!string.IsNullOrEmpty(iniFileLine.Trim()) && !iniFileLine.StartsWith(";", StringComparison.OrdinalIgnoreCase))
+                if (!string.IsNullOrWhiteSpace(iniFileLine) && !iniFileLine.StartsWith(";", StringComparison.OrdinalIgnoreCase))
                 {
                     if (iniFileLine.StartsWith("[", StringComparison.OrdinalIgnoreCase) && iniFileLine.EndsWith("]", StringComparison.OrdinalIgnoreCase))
                     {
@@ -86,21 +90,24 @@ public IniFileReader(string fileName)
         /// <summary>
         /// Gets a <see cref="ReadOnlyCollection{T}"/> containing the names of the sections in the .INI file.
         /// </summary>
-        public ReadOnlyCollection<string> SectionNames
-        {
-            get
-            {
-                List<string> keyList = new List<string>(this.iniFileStore.Keys);
-                return new ReadOnlyCollection<string>(keyList);
-            }
-        }
+        public ReadOnlyCollection<string> SectionNames => new ReadOnlyCollection<string>(new List<string>(this.iniFileStore.Keys));
 
         /// <summary>
         /// Gets a value from the .INI file.
         /// </summary>
         /// <param name="sectionName">The section in which to find the key-value pair.</param>
         /// <param name="valueName">The key of the key-value pair.</param>
         /// <returns>The value associated with the given section and key.</returns>
+        /// <exception cref="ArgumentNullException">
+        /// <para>If <paramref name="sectionName"/> is <see langword="null"/> or <see cref="string.Empty"/>.</para>
+        /// <para>-or-</para>
+        /// <para>If <paramref name="valueName"/> is <see langword="null"/> or <see cref="string.Empty"/>.</para>
+        /// </exception>
+        /// <exception cref="ArgumentException">
+        /// <para>If no section named <paramref name="sectionName"/> exists.</para>
+        /// <para>-or-</para>
+        ///<para>If the section does not contain a value named <paramref name="valueName"/>.</para>
+        /// </exception>
         public string GetValue(string sectionName, string valueName)
         {
             if (string.IsNullOrEmpty(sectionName))
@@ -117,19 +124,17 @@ public string GetValue(string sectionName, string valueName)
 
             string lowerCaseValueName = valueName.ToUpperInvariant();
 
-            if (!this.iniFileStore.ContainsKey(lowerCaseSectionName))
+            if (!this.iniFileStore.TryGetValue(lowerCaseSectionName, out Dictionary<string, string>? section))
             {
                 throw new ArgumentException("Section does not exist: " + sectionName, nameof(sectionName));
             }
 
-            Dictionary<string, string> section = this.iniFileStore[lowerCaseSectionName];
-
-            if (!section.ContainsKey(lowerCaseValueName))
+            if (!section.TryGetValue(lowerCaseValueName, out string? value))
             {
                 throw new ArgumentException("Value does not exist: " + valueName, nameof(valueName));
             }
 
-            return section[lowerCaseValueName];
+            return value;
         }
     }
 }