Got at least one data fetching method working; turns out, we can't use a patched LogicStack to get the data

Vendor/EmbedIO-3.5.2/Utilities/Validate-Paths.cs

@@ -0,0 +1,95 @@
+using System;
+using System.IO;
+using System.Security;
+
+namespace EmbedIO.Utilities
+{
+    partial class Validate
+    {
+        private static readonly char[] InvalidLocalPathChars = GetInvalidLocalPathChars();
+
+        /// <summary>
+        /// Ensures that the value of an argument is a valid URL path
+        /// and normalizes it.
+        /// </summary>
+        /// <param name="argumentName">The name of the argument to validate.</param>
+        /// <param name="value">The value to validate.</param>
+        /// <param name="isBasePath">If set to <see langword="true"/><c>true</c>, the returned path
+        /// is ensured to end in a slash (<c>/</c>) character; otherwise, the returned path is
+        /// ensured to not end in a slash character unless it is <c>"/"</c>.</param>
+        /// <returns>The normalized URL path.</returns>
+        /// <exception cref="ArgumentNullException"><paramref name="value"/> is <see langword="null"/>.</exception>
+        /// <exception cref="ArgumentException">
+        /// <para><paramref name="value"/> is empty.</para>
+        /// <para>- or -</para>
+        /// <para><paramref name="value"/> does not start with a slash (<c>/</c>) character.</para>
+        /// </exception>
+        /// <seealso cref="Utilities.UrlPath.Normalize"/>
+        public static string UrlPath(string argumentName, string value, bool isBasePath)
+        {
+            var exception = Utilities.UrlPath.ValidateInternal(argumentName, value);
+            if (exception != null)
+                throw exception;
+
+            return Utilities.UrlPath.Normalize(value, isBasePath);
+        }
+
+        /// <summary>
+        /// Ensures that the value of an argument is a valid local path
+        /// and, optionally, gets the corresponding full path.
+        /// </summary>
+        /// <param name="argumentName">The name of the argument to validate.</param>
+        /// <param name="value">The value to validate.</param>
+        /// <param name="getFullPath"><see langword="true"/> to get the full path, <see langword="false"/> to leave the path as is..</param>
+        /// <returns>The local path, or the full path if <paramref name="getFullPath"/> is <see langword="true"/>.</returns>
+        /// <exception cref="ArgumentNullException"><paramref name="value"/> is <see langword="null"/>.</exception>
+        /// <exception cref="ArgumentException">
+        /// <para><paramref name="value"/> is empty.</para>
+        /// <para>- or -</para>
+        /// <para><paramref name="value"/> contains only white space.</para>
+        /// <para>- or -</para>
+        /// <para><paramref name="value"/> contains one or more invalid characters.</para>
+        /// <para>- or -</para>
+        /// <para><paramref name="getFullPath"/> is <see langword="true"/> and the full path could not be obtained.</para>
+        /// </exception>
+        public static string LocalPath(string argumentName, string value, bool getFullPath)
+        {
+            if (value == null)
+                throw new ArgumentNullException(argumentName);
+
+            if (value.Length == 0)
+                throw new ArgumentException("Local path is empty.", argumentName);
+
+            if (string.IsNullOrWhiteSpace(value))
+                throw new ArgumentException("Local path contains only white space.", argumentName);
+
+            if (value.IndexOfAny(InvalidLocalPathChars) >= 0)
+                throw new ArgumentException("Local path contains one or more invalid characters.", argumentName);
+
+            if (getFullPath)
+            {
+                try
+                {
+                    value = Path.GetFullPath(value);
+                }
+                catch (Exception e) when (e is ArgumentException || e is SecurityException || e is NotSupportedException || e is PathTooLongException)
+                {
+                    throw new ArgumentException("Could not get the full local path.", argumentName, e);
+                }
+            }
+
+            return value;
+        }
+
+        private static char[] GetInvalidLocalPathChars()
+        {
+            var systemChars = Path.GetInvalidPathChars();
+            var p = systemChars.Length;
+            var result = new char[p + 2];
+            Array.Copy(systemChars, result, p);
+            result[p++] = '*';
+            result[p] = '?';
+            return result;
+        }
+    }
+}