Update

Author: JamesNK

src/Grpc/JsonTranscoding/src/Microsoft.AspNetCore.Grpc.JsonTranscoding/Internal/Json/EnumNameHelpers.cs

@@ -30,8 +30,7 @@ internal static class JsonNamingHelpers
             resolvedName = value;
         }
 
-        var valueDescriptor = enumDescriptor.FindValueByName(resolvedName);
-        return valueDescriptor;
+        return enumDescriptor.FindValueByName(resolvedName);
     }
 
     internal static string? GetEnumFieldWriteName(EnumDescriptor enumDescriptor, object value, GrpcJsonSettings settings)
@@ -91,9 +90,10 @@ private static EnumMapping GetEnumMapping(string enumName, Type enumType)
         return new EnumMapping { WriteMapping = writeMapping, StripEnumPrefixMapping = stripEnumPrefixMapping };
     }
 
+    // Remove the prefix from the specified value. Ignore case and underscores in the comparison.
     private static string TryRemovePrefix(string prefix, string value)
     {
-        var normalizedPrefix = new string(prefix.Where(c => c != '_').Select(char.ToLowerInvariant).ToArray());
+        var normalizedPrefix = prefix.Replace("_", string.Empty, StringComparison.Ordinal).ToLowerInvariant();
 
         var prefixIndex = 0;
         var valueIndex = 0;
@@ -131,7 +131,11 @@ private static string TryRemovePrefix(string prefix, string value)
     private static string GetEnumValueName(string enumName, string valueName)
     {
         var result = TryRemovePrefix(enumName, valueName);
-        return char.IsDigit(result[0]) ? $"_{result}" : result;
+
+        // Prefix name starting with a digit with an underscore to ensure it is a valid identifier.
+        return result.Length > 0 && char.IsDigit(result[0])
+            ? $"_{result}"
+            : result;
     }
 
     private sealed class EnumMapping