Handles null key in FindPercentComplete method

Modifies the FindPercentComplete method to return null
when the key is null.

Updates the unit test to reflect the change in behavior.

Updates styling for elements related to current page display.

Author: BenjaminMichaelis

EssentialCSharp.Web.Tests/SiteMappingTests.cs

@@ -84,7 +84,7 @@ public void FindCSyntaxFundamentalsSanitizedWithAnchorReturnsCorrectSiteMap()
     }
 
     [Fact]
-    public void FindPercentComplete_KeyIsNull_ThrowsArgumentNullException()
+    public void FindPercentComplete_KeyIsNull_ReturnsNull()
     {
         // Arrange
 

EssentialCSharp.Web/Extensions/SiteMappingListExtensions.cs

@@ -29,7 +29,7 @@ public static class SiteMappingListExtensions
     /// Finds percent complete based on a key.
     /// </summary>
     /// <param name="siteMappings">IList of SiteMappings</param>
-    /// <param name="key">If null, uses the first key in the list</param>
+    /// <param name="key">The key to search for. If null, returns null.</param>
     /// <returns>Returns a formatted double for use as the percent complete.</returns>
     public static string? FindPercentComplete(this IList<SiteMapping> siteMappings, string? key)
     {
@@ -39,7 +39,7 @@ public static class SiteMappingListExtensions
         }
         if (key.Trim().Length is 0)
         {
-            throw new ArgumentException("Parameter key is whitespace or empty: ", nameof(key));
+            throw new ArgumentException("Parameter 'key' cannot be null or whitespace.", nameof(key));
         }
         int currentMappingCount = 0;
         int overallMappingCount = 0;

EssentialCSharp.Web/Views/Shared/_Layout.cshtml

@@ -121,10 +121,10 @@
                         </div>
                     </div>
 
-                    <a v-if="chapterParentPage" :href="chapterParentPage.href" class="menu menu-chapter-title text-light">
+                    <a v-if="chapterParentPage" :href="chapterParentPage.href" class="page-menu menu-chapter-title text-light">
                         <span v-cloak>{{chapterParentPage.title}}</span>
                     </a>
-                    <div class="menu menu-progress text-light" v-if="isContentPage">
+                    <div class="page-menu menu-progress text-light" v-if="isContentPage">
                         <span v-cloak>{{percentComplete}}%</span>
                     </div>
 

EssentialCSharp.Web/wwwroot/css/styles.css

@@ -224,7 +224,7 @@ a:hover {
   }
 }
 
-.menu {
+.page-menu {
   white-space: nowrap;
   overflow: hidden;
   text-decoration: none;