From 26c7bb62477de7059f0687ff75c0d172d8e7c4aa Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Raffael=20Sch=C3=A4rer?= <rs@devigus.com>
Date: Tue, 20 Feb 2024 16:28:25 +0100
Subject: [PATCH] Addresses an issue with collection expressions in C# 12
 regarding IReadOnlyList

---
 .../EditContextFluentValidationExtensions.cs           | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/src/Blazored.FluentValidation/EditContextFluentValidationExtensions.cs b/src/Blazored.FluentValidation/EditContextFluentValidationExtensions.cs
index 24fba59..7ab8ab8 100644
--- a/src/Blazored.FluentValidation/EditContextFluentValidationExtensions.cs
+++ b/src/Blazored.FluentValidation/EditContextFluentValidationExtensions.cs
@@ -199,6 +199,16 @@ private static FieldIdentifier ToFieldIdentifier(in EditContext editContext, in
                         var indexerValue = int.Parse(nextToken);
                         newObj = array[indexerValue];
                     }
+                    else if (obj is IReadOnlyList<object> readOnlyList)
+                    {
+                        // Addresses an issue with collection expressions in C# 12 regarding IReadOnlyList:
+                        // Generates a <>z__ReadOnlyArray which:
+                        // - lacks an Item property, and
+                        // - cannot be cast to object[] successfully.
+                        // This workaround accesses elements directly using an indexer.
+                        var indexerValue = int.Parse(nextToken);
+                        newObj = readOnlyList[indexerValue];
+                    }
                     else
                     {
                         throw new InvalidOperationException($"Could not find indexer on object of type {obj.GetType().FullName}.");