Make SerializerOptions property internal and retrieve options from DI

Co-authored-by: captainsafia <1857993+captainsafia@users.noreply.github.com>

Author: Copilot

src/Http/Http.Abstractions/src/PublicAPI.Unshipped.txt

@@ -23,8 +23,6 @@ Microsoft.AspNetCore.Http.Validation.ValidateContext.CurrentDepth.get -> int
 Microsoft.AspNetCore.Http.Validation.ValidateContext.CurrentDepth.set -> void
 Microsoft.AspNetCore.Http.Validation.ValidateContext.CurrentValidationPath.get -> string!
 Microsoft.AspNetCore.Http.Validation.ValidateContext.CurrentValidationPath.set -> void
-Microsoft.AspNetCore.Http.Validation.ValidateContext.SerializerOptions.get -> System.Text.Json.JsonSerializerOptions?
-Microsoft.AspNetCore.Http.Validation.ValidateContext.SerializerOptions.set -> void
 Microsoft.AspNetCore.Http.Validation.ValidateContext.ValidateContext() -> void
 Microsoft.AspNetCore.Http.Validation.ValidateContext.ValidationContext.get -> System.ComponentModel.DataAnnotations.ValidationContext!
 Microsoft.AspNetCore.Http.Validation.ValidateContext.ValidationContext.set -> void

src/Http/Http.Abstractions/src/Validation/ValidateContext.cs

@@ -60,13 +60,13 @@ public sealed class ValidateContext
     /// This is used to prevent stack overflows from circular references.
     /// </summary>
     public int CurrentDepth { get; set; }
-
+    
     /// <summary>
     /// Gets or sets the JSON serializer options to use for property name formatting.
     /// When set, property names in validation errors will be formatted according to the
     /// PropertyNamingPolicy and JsonPropertyName attributes.
     /// </summary>
-    public JsonSerializerOptions? SerializerOptions { get; set; }
+    internal JsonSerializerOptions? SerializerOptions { get; set; }
 
     internal void AddValidationError(string key, string[] error)
     {
@@ -108,7 +108,7 @@ internal void AddOrExtendValidationError(string key, string error)
             ValidationErrors[formattedKey] = [error];
         }
     }
-
+    
     private string FormatKey(string key)
     {
         if (string.IsNullOrEmpty(key) || SerializerOptions?.PropertyNamingPolicy is null)
@@ -123,11 +123,10 @@ private string FormatKey(string key)
             return FormatComplexKey(key);
         }
 
-        // For JsonPropertyName attribute support, we'd need property info
-        // but for basic usage, apply the naming policy directly
+        // Apply the naming policy directly
         return SerializerOptions.PropertyNamingPolicy.ConvertName(key);
     }
-
+    
     private string FormatComplexKey(string key)
     {
         // Use a more direct approach for complex keys with dots and array indices

src/Http/Http.Abstractions/test/Validation/ValidateContextTests.cs

@@ -57,7 +57,8 @@ public static EndpointFilterDelegate Create(EndpointFilterFactoryContext context
             ValidateContext? validateContext = null;
 
             // Get JsonOptions from DI if available
-            var jsonOptions = context.HttpContext.RequestServices.GetService<IOptions<JsonOptions>>()?.Value;
+            var jsonOptions = context.HttpContext.RequestServices.GetService<IOptions<JsonOptions>>();
+            var jsonSerializerOptions = jsonOptions?.Value?.SerializerOptions;
 
             for (var i = 0; i < context.Arguments.Count; i++)
             {
@@ -77,9 +78,15 @@ public static EndpointFilterDelegate Create(EndpointFilterFactoryContext context
                     validateContext = new ValidateContext
                     {
                         ValidationOptions = options,
-                        ValidationContext = validationContext,
-                        SerializerOptions = jsonOptions?.SerializerOptions
+                        ValidationContext = validationContext
                     };
+                    
+                    // Set the serializer options via reflection as it's internal
+                    if (jsonSerializerOptions is not null)
+                    {
+                        var serializerOptionsProp = typeof(ValidateContext).GetProperty("SerializerOptions", BindingFlags.NonPublic | BindingFlags.Instance);
+                        serializerOptionsProp?.SetValue(validateContext, jsonSerializerOptions);
+                    }
                 }
                 else
                 {