Fix #278 (#279)

src/Unosquare.Labs.EmbedIO/Core/VirtualPath.cs

@@ -24,7 +24,14 @@ public VirtualPath(string baseUrlPath, string baseLocalPath)
 
         public string BaseLocalPath { get; }
 
-        internal bool CanMapUrlPath(string urlPath) => urlPath.StartsWith(BaseUrlPath, StringComparison.Ordinal);
+        // Base paths are forced to end with a slash,
+        // while requested paths are forced to NOT end with a slash.
+        // Virtual path "/media/" can map "/media/file.jpg"
+        // but it can also map "/media" (without the slash).
+
+        internal bool CanMapUrlPath(string urlPath)
+            => urlPath.StartsWith(BaseUrlPath, StringComparison.Ordinal)
+            || (urlPath.Length == BaseUrlPath.Length - 1 && BaseUrlPath.StartsWith(urlPath, StringComparison.Ordinal));
 
         internal bool TryMapUrlPathLoLocalPath(string urlPath, out string localPath)
         {
@@ -34,7 +41,11 @@ internal bool TryMapUrlPathLoLocalPath(string urlPath, out string localPath)
                 return false;
             }
 
-            var relativeUrlPath = urlPath.Substring(BaseUrlPath.Length);
+            // The only case where CanMapUrlPath returns true for a path shorter than BaseUrlPath
+            // is urlPath == (BaseUrlPath minus the final slash).
+            var relativeUrlPath = urlPath.Length < BaseUrlPath.Length
+                ? string.Empty
+                : urlPath.Substring(BaseUrlPath.Length);
             localPath = Path.Combine(BaseLocalPath, relativeUrlPath.Replace('/', Path.DirectorySeparatorChar));
             return true;
         }