Fix remaining violations: IDE1006/IDE0060/IDE0090/CA1859/IDE0130

- IDE1006 naming: renamed 89 private/internal static fields to s_ prefix
  and instance fields to _ prefix; suppressed public API constants that
  can't be renamed without breaking changes (iOSBroker*, Prompt.*, XmlNamespace.*)
- IDE1006: renamed private Base64* constants, IosBroker* internal members
- IDE0060: added #pragma suppress for 4 unused params reserved for future use
- IDE0090: fixed new() in 8 more files (HashSet, StringBuilder, Dictionary)
- CA1859: changed IDictionary/ISet/IRegionManager to concrete types in 5 files
- IDE0130: suppressed globally - intentional flat namespace Microsoft.Identity.Client
- editorconfig: scoped static_fields naming rule to private+internal (not public)
  to avoid false positives on public static fields

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: Robbie-Microsoft

.editorconfig

@@ -75,6 +75,7 @@ dotnet_naming_rule.static_fields_should_have_prefix.style = static_prefix_style
 
 dotnet_naming_symbols.static_fields.applicable_kinds   = field
 dotnet_naming_symbols.static_fields.required_modifiers = static
+dotnet_naming_symbols.static_fields.applicable_accessibilities = private, internal, private_protected
 
 dotnet_naming_style.static_prefix_style.required_prefix = s_
 dotnet_naming_style.static_prefix_style.capitalization = camel_case 
@@ -884,6 +885,11 @@ dotnet_diagnostic.IDE0039.severity = none
 dotnet_diagnostic.IDE0051.severity = none
 dotnet_diagnostic.IDE0052.severity = none
 
+# Namespace does not match folder structure (IDE0130)
+# Disabled: intentional flat namespace design - all public types use Microsoft.Identity.Client
+# regardless of subfolder, to maintain a clean public API surface
+dotnet_diagnostic.IDE0130.severity = none
+
 # Use range subscript operator (x[^1]) - requires .NET 5+ (System.Index not available in net462/netstandard2.0)
 dotnet_diagnostic.IDE0056.severity = none
 

src/client/Microsoft.Identity.Client/ApiConfig/AcquireTokenInteractiveParameterBuilder.cs

@@ -251,14 +251,14 @@ private AcquireTokenInteractiveParameterBuilder WithParentObject(object parent)
         }
 
 #if NET_CORE
-        private static readonly Type WinUIWindowType = Type.GetType("Microsoft.UI.Xaml.Window, Microsoft.WinUI");
+        private static readonly Type s_winUIWindowType = Type.GetType("Microsoft.UI.Xaml.Window, Microsoft.WinUI");
 
         /// <summary>
         /// Checks if an object is a WinUI3 Window or derives from one
         /// </summary>
         private static bool IsWinUI3Window(object obj)
         {
-            return obj != null && WinUIWindowType?.IsAssignableFrom(obj.GetType()) == true;
+            return obj != null && s_winUIWindowType?.IsAssignableFrom(obj.GetType()) == true;
         }
 #endif
 

src/client/Microsoft.Identity.Client/ApiConfig/Parameters/AcquireTokenInteractiveParameters.cs

@@ -14,7 +14,7 @@ namespace Microsoft.Identity.Client.ApiConfig.Parameters
 
     internal class AcquireTokenInteractiveParameters : IAcquireTokenParameters
     {
-        public Prompt Prompt { get; set; } = Prompt.NotSpecified;
+        public Prompt Prompt { get; set; } = Prompt.s_notSpecified;
         public CoreUIParent UiParent { get; } = new CoreUIParent();
 
         /// <summary>

src/client/Microsoft.Identity.Client/AppConfig/AuthorityInfo.cs

@@ -304,7 +304,7 @@ internal bool IsDefaultAuthority
             }
         }
 
-        internal static readonly char[] separator =
+        internal static readonly char[] s_separator =
                 [
                     '/'
                 ];
@@ -437,7 +437,7 @@ private static bool IsCiamAuthority(Uri authorityUri)
         private static string[] GetPathSegments(string absolutePath)
         {
             string[] pathSegments = absolutePath.Split(
-                separator,
+                s_separator,
                 StringSplitOptions.RemoveEmptyEntries);
 
             return pathSegments;

src/client/Microsoft.Identity.Client/AuthenticationHeaderParser.cs

@@ -19,7 +19,7 @@ namespace Microsoft.Identity.Client
     /// </summary>
     public class AuthenticationHeaderParser
     {
-        private static readonly Lazy<IMsalHttpClientFactory> _httpClientFactory = new(
+        private static readonly Lazy<IMsalHttpClientFactory> s_httpClientFactory = new(
                                                                           () => PlatformProxyFactory.CreatePlatformProxy(null).CreateDefaultHttpClientFactory());
 
         /// <summary>
@@ -116,7 +116,7 @@ public static AuthenticationHeaderParser ParseAuthenticationHeaders(HttpResponse
         /// </summary>
         internal static HttpClient GetHttpClient()
         {
-            return _httpClientFactory.Value.GetHttpClient();
+            return s_httpClientFactory.Value.GetHttpClient();
         }
 
         /// <summary>

src/client/Microsoft.Identity.Client/AuthenticationInfoParameters.cs

@@ -61,7 +61,7 @@ public static AuthenticationInfoParameters CreateFromResponseHeaders(HttpRespons
                 {
                     var authInfoValue = authInfoValueList.FirstOrDefault();
                     var AuthValuesSplit = authInfoValue.Split([' '], 2);
-                    IDictionary<string, string> paramValues;
+                    Dictionary<string, string> paramValues;
 
                     if (AuthValuesSplit.Length != 2)
                     {

src/client/Microsoft.Identity.Client/Cache/Items/CacheSerializationContract.cs

@@ -19,7 +19,7 @@ namespace Microsoft.Identity.Client.Cache.Items
     internal class CacheSerializationContract(IDictionary<string, JToken> unknownNodes)
     {
 #if SUPPORTS_SYSTEM_TEXT_JSON
-        private static readonly JsonSerializerOptions NeverIgnoreJsonOptions = new()
+        private static readonly JsonSerializerOptions s_neverIgnoreJsonOptions = new()
         {
             DefaultIgnoreCondition = System.Text.Json.Serialization.JsonIgnoreCondition.Never
         };
@@ -150,7 +150,7 @@ static IEnumerable<JObject> GetElement(JObject root, string key)
 #endif
         }
 
-        private static IDictionary<string, JToken> ExtractUnknownNodes(JObject root)
+        private static Dictionary<string, JToken> ExtractUnknownNodes(JObject root)
         {
 #if SUPPORTS_SYSTEM_TEXT_JSON
             return root
@@ -220,7 +220,7 @@ internal string ToJsonString()
 #endif
             }
 #if SUPPORTS_SYSTEM_TEXT_JSON
-            return root.ToJsonString(NeverIgnoreJsonOptions);
+            return root.ToJsonString(s_neverIgnoreJsonOptions);
 #else
             return JsonConvert.SerializeObject(
                 root,

src/client/Microsoft.Identity.Client/Cache/Items/MsalAccessTokenCacheItem.cs

@@ -232,7 +232,7 @@ internal void InitCacheKey()
                 ScopeString,
                 _extraKeyParts);
 
-            iOSCacheKeyLazy = new Lazy<IiOSKey>(InitiOSKey);
+            _iOSCacheKeyLazy = new Lazy<IiOSKey>(InitiOSKey);
         }
 
         internal string ToLogString(bool piiEnabled = false)
@@ -307,8 +307,8 @@ internal string TenantId
         /// </summary>
         internal IDictionary<string, string> PersistedCacheParameters { get; private set; }
 
-        private Lazy<IiOSKey> iOSCacheKeyLazy;
-        public IiOSKey iOSCacheKey => iOSCacheKeyLazy.Value;
+        private Lazy<IiOSKey> _iOSCacheKeyLazy;
+        public IiOSKey iOSCacheKey => _iOSCacheKeyLazy.Value;
 
         internal static MsalAccessTokenCacheItem FromJsonString(string json)
         {

src/client/Microsoft.Identity.Client/Cache/Items/MsalAccountCacheItem.cs

@@ -132,8 +132,8 @@ internal MsalAccountCacheItem(
         internal IDictionary<string, string> WamAccountIds { get; set; }
         public string CacheKey { get; private set; }
 
-        private Lazy<IiOSKey> iOSCacheKeyLazy;
-        public IiOSKey iOSCacheKey => iOSCacheKeyLazy.Value;
+        private Lazy<IiOSKey> _iOSCacheKeyLazy;
+        public IiOSKey iOSCacheKey => _iOSCacheKeyLazy.Value;
 
         private void Init(
             string environment,
@@ -167,7 +167,7 @@ internal void InitCacheKey()
         {
             CacheKey = $"{HomeAccountId}{MsalCacheKeys.CacheKeyDelimiter}{Environment}{MsalCacheKeys.CacheKeyDelimiter}{TenantId}";
 
-            iOSCacheKeyLazy = new Lazy<IiOSKey>(InitiOSKey);
+            _iOSCacheKeyLazy = new Lazy<IiOSKey>(InitiOSKey);
         }
 
         #region iOS
@@ -183,7 +183,7 @@ private IiOSKey InitiOSKey()
             // This is a known issue.
             // Normally AuthorityType should be passed here but since while building the MsalAccountCacheItem it is defaulted to "MSSTS",
             // keeping the default value here.
-            int iOSType = MsalCacheKeys.iOSAuthorityTypeToAttrType[CacheAuthorityType.MSSTS.ToString()];
+            int iOSType = MsalCacheKeys.s_iOSAuthorityTypeToAttrType[CacheAuthorityType.MSSTS.ToString()];
 
             return new IosKey(iOSAccount, iOSService, iOSGeneric, iOSType);
         }

src/client/Microsoft.Identity.Client/Cache/Items/MsalAppMetadataCacheItem.cs

@@ -36,7 +36,7 @@ private void InitCacheKey()
             CacheKey = ($"{StorageJsonKeys.AppMetadata}{MsalCacheKeys.CacheKeyDelimiter}" +
                 $"{Environment}{MsalCacheKeys.CacheKeyDelimiter}{ClientId}").ToLowerInvariant();
 
-            iOSCacheKeyLazy = new Lazy<IiOSKey>(InitiOSKey);
+            _iOSCacheKeyLazy = new Lazy<IiOSKey>(InitiOSKey);
         }
 
         #region iOS
@@ -70,8 +70,8 @@ private IiOSKey InitiOSKey()
         public string FamilyId { get; }
         public string CacheKey { get; private set; }
 
-        private Lazy<IiOSKey> iOSCacheKeyLazy;
-        public IiOSKey iOSCacheKey => iOSCacheKeyLazy.Value;
+        private Lazy<IiOSKey> _iOSCacheKeyLazy;
+        public IiOSKey iOSCacheKey => _iOSCacheKeyLazy.Value;
 
         internal static MsalAppMetadataCacheItem FromJsonString(string json)
         {