Fix ToEnumString performance

src/Framework/Framework/Controls/HtmlGenericControl.cs

@@ -370,19 +370,22 @@ private void AddHtmlAttribute(IHtmlWriter writer, string name, object? value)
             {
                 writer.AddAttribute(name, ReflectionUtils.ToEnumString(enumValue.GetType(), enumValue.ToString()));
             }
-            else if (value is Guid)
-            {
-                writer.AddAttribute(name, value.ToString());
-            }
-            else if (ReflectionUtils.IsNumericType(value.GetType()))
-            {
-                writer.AddAttribute(name, Convert.ToString(value, CultureInfo.InvariantCulture));
-            }
-            else
-            {
-                // DateTime and related are not supported here intentionally.
-                // It is not clear in which format it should be rendered - on some places, the HTML specs requires just yyyy-MM-dd,
-                // but in case of Web Components, the users may want to pass the whole date, or use a specific format
+        }
+
+        private static string AttributeValueToString(object? value) =>
+            value switch {
+                null => "",
+                string str => str,
+                Enum enumValue => ReflectionUtils.ToEnumString(enumValue.GetType(), enumValue.ToString()),
+                Guid guid => guid.ToString(),
+                _ when ReflectionUtils.IsNumericType(value.GetType()) => Convert.ToString(value, CultureInfo.InvariantCulture) ?? "",
+                System.Collections.IEnumerable =>
+                    throw new NotSupportedException($"Attribute value of type '{value.GetType().ToCode(stripNamespace: true)}' is not supported. Consider concatenating the values into a string or use the HtmlGenericControl.AttributeList if you need to pass multiple values."),
+                _ =>
+
+                    // DateTime and related are not supported here intentionally.
+                    // It is not clear in which format it should be rendered - on some places, the HTML specs requires just yyyy-MM-dd,
+                    // but in case of Web Components, the users may want to pass the whole date, or use a specific format
 
                 throw new NotSupportedException($"Attribute value of type '{value.GetType().FullName}' is not supported. Please convert the value to string, e. g. by using ToString()");
             }

src/Framework/Framework/Utils/ReflectionUtils.cs

@@ -472,20 +472,12 @@ public static string GetTypeHash(this Type type)
             member is TypeInfo type ? type.AsType() :
             throw new NotImplementedException($"Could not get return type of member {member.GetType().FullName}");
 
-        private static readonly ConcurrentDictionary<Type, bool> hasEnumMemberFieldCache = new();
-
-        public static string ToEnumString<T>(this T instance) where T : Enum
+        public static string ToEnumString<T>(this T instance) where T : struct, Enum
         {
-            var enumType = instance.GetType();
-
-            var hasEnumMemberField = hasEnumMemberFieldCache.GetOrAdd(enumType,
-                t => t.GetFields(BindingFlags.Public | BindingFlags.Static)
-                    .Any(field => field.IsDefined(typeof(EnumMemberAttribute), false)));
-
             var name = instance.ToString();
-			if (!hasEnumMemberField)
-				return name;
-			return ToEnumString(enumType, name);
+            if (!EnumInfo<T>.HasEnumMemberField)
+                return name;
+            return ToEnumString(typeof(T), name);
         }
 
         public static string ToEnumString(Type enumType, string name)
@@ -501,6 +493,23 @@ public static string ToEnumString(Type enumType, string name)
             }
             return name;
         }
+
+        internal static class EnumInfo<T> where T: struct, Enum
+        {
+            internal static readonly bool HasEnumMemberField;
+
+            static EnumInfo()
+            {
+                foreach (var field in typeof(T).GetFields(BindingFlags.Public | BindingFlags.Static))
+                {
+                    if (field.IsDefined(typeof(EnumMemberAttribute), false))
+                    {
+                        HasEnumMemberField = true;
+                        break;
+                    }
+                }
+            }
+        }
 
         public static Type GetDelegateType(MethodInfo methodInfo)
         {