chore: import upstream snapshot with attribution

dotnet/samples/Demos/AIModelRouter/CustomRouter.cs

@@ -0,0 +1,41 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+#pragma warning disable SKEXP0001
+#pragma warning disable SKEXP0010
+#pragma warning disable CA2249 // Consider using 'string.Contains' instead of 'string.IndexOf'
+
+namespace AIModelRouter;
+
+/// <summary>
+/// This class is for demonstration purposes only.
+/// In a real-world scenario, you would use a more sophisticated routing mechanism, such as another local model for
+/// deciding which service to use based on the user's input or any other criteria.
+/// </summary>
+internal sealed class CustomRouter()
+{
+    /// <summary>
+    /// Returns the best service id to use based on the user's input.
+    /// This demonstration uses a simple logic where your input is checked for specific keywords as a deciding factor,
+    /// if no keyword is found it defaults to the first service in the list.
+    /// </summary>
+    /// <param name="lookupPrompt">User's input prompt</param>
+    /// <param name="serviceIds">List of service ids to choose from in order of importance, defaulting to the first</param>
+    /// <returns>Service id.</returns>
+    internal string GetService(string lookupPrompt, List<string> serviceIds)
+    {
+        // The order matters, if the keyword is not found, the first one is used.
+        foreach (var serviceId in serviceIds)
+        {
+            if (Contains(lookupPrompt, serviceId))
+            {
+                return serviceId;
+            }
+        }
+
+        return serviceIds[0];
+    }
+
+    // Ensure compatibility with both netstandard2.0 and net8.0 by using IndexOf instead of Contains
+    private static bool Contains(string prompt, string pattern)
+        => prompt.IndexOf(pattern, StringComparison.CurrentCultureIgnoreCase) >= 0;
+}