JamesNK/Newtonsoft.Json · error · ArgumentException

Must specify valid information for parsing in the string.

Error message

Must specify valid information for parsing in the string.

What it means

ParseEnum (EnumUtils.cs:281-293) scans the input string for the first non-whitespace character to begin parsing. If the entire string is whitespace (firstNonWhitespaceIndex stays -1), it throws ArgumentException at EnumUtils.cs:292 — there is no content to parse into an enum value.

Source

Thrown at Src/Newtonsoft.Json/Utilities/EnumUtils.cs:292

            // first check if the entire text (including commas) matches a resolved name
            int? matchingIndex = FindIndexByName(resolvedNames, value, 0, value.Length, StringComparison.Ordinal);
            if (matchingIndex != null)
            {
                return Enum.ToObject(enumType, enumValues[matchingIndex.Value]);
            }

            int firstNonWhitespaceIndex = -1;
            for (int i = 0; i < value.Length; i++)
            {
                if (!char.IsWhiteSpace(value[i]))
                {
                    firstNonWhitespaceIndex = i;
                    break;
                }
            }
            if (firstNonWhitespaceIndex == -1)
            {
                throw new ArgumentException("Must specify valid information for parsing in the string.");
            }

            // check whether string is a number and parse as a number value
            char firstNonWhitespaceChar = value[firstNonWhitespaceIndex];
            if (char.IsDigit(firstNonWhitespaceChar) || firstNonWhitespaceChar == '-' || firstNonWhitespaceChar == '+')
            {
                Type underlyingType = Enum.GetUnderlyingType(enumType);

                value = value.Trim();
                object? temp = null;

                try
                {
                    temp = Convert.ChangeType(value, underlyingType, CultureInfo.InvariantCulture);
                }
                catch (FormatException)
                {
                    // We need to Parse this as a String instead. There are cases

View on GitHub (pinned to 4f73e74372)

Solutions

1. Validate the string with !string.IsNullOrWhiteSpace(value) before parsing.
2. Treat blank/empty as the enum's default value (or a designated 'Unknown' member) instead of calling ParseEnum.
3. Sanitize incoming JSON/string values at the boundary.
4. Use StringEnumConverter with a fallback for null/empty.

Example fix

// before
var e = (MyEnum)Enum.Parse(typeof(MyEnum), s); // s = "   " -> throws
// after
if (string.IsNullOrWhiteSpace(s)) return default(MyEnum);
var e = (MyEnum)Enum.Parse(typeof(MyEnum), s.Trim());

// Reject blank strings before parsing an enum.
if (string.IsNullOrWhiteSpace(value)) throw new ArgumentException("Enum value must not be blank.");
value = value.Trim();

static bool IsParsableEnumString(string? s) => !string.IsNullOrWhiteSpace(s);

try { return EnumUtils.ParseEnum(enumType, null, value, false); } catch (ArgumentException ex) when (ex.Message.Contains("valid information for parsing")) { return default; }

When it happens

Trigger: An empty or all-whitespace string is supplied as an enum value — e.g. JSON `"status": " "` for an enum field, or a value that was trimmed to empty.

Common situations: Whitespace-only enum strings in JSON payloads; upstream trimming producing empty values; default/missing fields represented as blank strings; integration with APIs that emit empty for unset.

Related errors

• Unexpected merge array handling when merging JSON.
• value
• value
• Enum name '{0}' already exists on enum '{1}'.
• Enum type {0} is not a set of flags.

AI-assisted analysis of JamesNK/Newtonsoft.Json@4f73e74372 (2026-08-07). Data as JSON: /api/errors/7f8fd2056fb4b1d9. Report an issue: GitHub.