JamesNK/Newtonsoft.Json · error · ArgumentOutOfRangeException

Unexpected token type: {0}

Error message

Unexpected token type: {0}

What it means

Thrown by JsonValidatingReader's CurrentSchemas getter default case when the current scope token type is none of the handled cases (None, Object, Array/Property via PropertyName, Constructor). This indicates an unexpected/unhandled JTokenType during schema validation and is a bug or unsupported-token scenario in the validating reader, surfaced as ArgumentOutOfRangeException naming the offending token type.

Source

Thrown at Src/Newtonsoft.Json/JsonValidatingReader.cs:259

                                        if (schema.Items.Count > (_currentScope.ArrayItemCount - 1))
                                        {
                                            schemas.Add(schema.Items[_currentScope.ArrayItemCount - 1]);
                                        }
                                    }

                                    if (schema.AllowAdditionalItems && schema.AdditionalItems != null)
                                    {
                                        schemas.Add(schema.AdditionalItems);
                                    }
                                }
                            }

                            return schemas;
                        }
                    case JTokenType.Constructor:
                        return EmptySchemaList;
                    default:
                        throw new ArgumentOutOfRangeException("TokenType", "Unexpected token type: {0}".FormatWith(CultureInfo.InvariantCulture, _currentScope.TokenType));
                }
            }
        }

        private void RaiseError(string message, JsonSchemaModel schema)
        {
            IJsonLineInfo lineInfo = this;

            string exceptionMessage = (lineInfo.HasLineInfo())
                ? message + " Line {0}, position {1}.".FormatWith(CultureInfo.InvariantCulture, lineInfo.LineNumber, lineInfo.LinePosition)
                : message;

            OnValidationEvent(new JsonSchemaException(exceptionMessage, null, Path, lineInfo.LineNumber, lineInfo.LinePosition));
        }

        private void OnValidationEvent(JsonSchemaException exception)
        {
            ValidationEventHandler handler = ValidationEventHandler;

View on GitHub (pinned to 4f73e74372)

Solutions

1. Strip Comment/Raw/unexpected tokens (e.g. read from JsonTextReader with default settings, or filter) before validation.
2. Use JsonSchema (or migrate to System.Text.Schema / Newtonsoft.Json.Schema) with a schema whose constructs match the token types emitted.
3. If you control the reader, only emit Object/Array/PropertyName/Primitive tokens during validation.

Example fix

// before
// reader emits Comment tokens into validating reader

// after
var textReader = new JsonTextReader(input); // does not emit schema-breaking tokens
using var validating = new JsonValidatingReader(textReader);

if (tokenType is JsonToken.Comment or JsonToken.Raw)
{
    // skip/filter token before validation
}

static bool IsSchemaHandledToken(JTokenType t)
    => t is JTokenType.Object or JTokenType.Array or JTokenType.Constructor
        or JTokenType.Property or JTokenType.None;

try
{
    while (validating.Read()) { /* ... */ }
}
catch (ArgumentOutOfRangeException ex) when (ex.Message.Contains("Unexpected token type"))
{
    // strip non-handled tokens (Comment/Raw) from the source and retry
}

When it happens

Trigger: A JSON token stream containing a token type the validating reader's schema model does not handle (e.g. Comment, Raw, or an unexpected JTokenType) while a schema scope is active; custom readers injecting non-standard tokens.

Common situations: Feeding a reader that emits Comment/Raw tokens into JsonValidatingReader; library version mismatch where new token types are not yet handled; malformed or preprocessed JSON introducing unusual tokens.

Understand the failure class

• Parsing and encoding errors: unexpected token, malformed input — why parsers reject input and how to find the real culprit.

Related errors

• CurrentPropertyName has not been set on scope.
• Cannot change schema while validating JSON.

AI-assisted analysis of JamesNK/Newtonsoft.Json@4f73e74372 (2026-08-07). Data as JSON: /api/errors/0e9447e7e621b2f9. Report an issue: GitHub.