What causes "Failed to parse the input" in BCUninstaller/Bulk-Crap-Uninstaller?

Pre-validate with GuidTools.GuidTryParse(s, out var g) (mentioned right below in the same file) and avoid the exception path entirely.

BCUninstaller/Bulk-Crap-Uninstaller · error · ArgumentException

Failed to parse the input

Error message

Failed to parse the input

What it means

Thrown by the GuidTools parse method (the catch-all wrapping new Guid(source)). The method first extracts content inside braces/parens; if the trimmed string still cannot be parsed by the Guid constructor (which throws FormatException for bad GUID strings), it is rethrown wrapped as ArgumentException("Failed to parse the input", ex). The inner exception preserves the original parse error.

Source

Thrown at source/KlocTools/Tools/GuidTools.cs:43

            if (source == null)
                throw new ArgumentNullException(nameof(source));

            try
            {
                var braceIndex = source.IndexOfAny(new[] {'{', '('});
                if (braceIndex >= 0)
                {
                    var endingBraceIndex = source.IndexOfAny(new[] {'}', ')'});
                    if (endingBraceIndex < 0)
                        throw new ArgumentException("Invalid brace format");

                    source = source.Substring(braceIndex, endingBraceIndex - braceIndex + 1);
                }
                return new Guid(source);
            }
            catch (Exception ex)
            {
                throw new ArgumentException("Failed to parse the input", ex);
            }
            //throw new NotImplementedException();
        }

        /// <summary>
        /// Try to parse the supplied string into a guid. Faster than catching exceptions.
        /// </summary>
        public static bool GuidTryParse(string s, out Guid result)
        {
            result = Guid.Empty;
            if (string.IsNullOrEmpty(s) || !GuidMatchRegex.IsMatch(s))
            {
                return false;
            }
            result = new Guid(s);
            return true;
        }

View on GitHub (pinned to 608321de98)

Solutions

Pre-validate with GuidTools.GuidTryParse(s, out var g) (mentioned right below in the same file) and avoid the exception path entirely.
Sanitise the input: trim whitespace and confirm it matches the standard 8-4-4-4-12 hex pattern before parsing.
If you read from a data source, log the raw string on failure (from ex.InnerException) to locate the bad row.

Example fix

// before
var g = GuidTools.ParseGuid(input); // throws on bad input

// after
if (GuidTools.GuidTryParse(input, out var g))
    Use(g);
else
    logger.Warn($"Ignoring malformed GUID: {input}");

Defensive patterns

Strategy: validation

Validate before calling

if (!GuidTools.GuidTryParse(input, out var g))
    return; // or surface a user-facing error
// use g

Type guard

static bool IsValidGuid(string s)
    => !string.IsNullOrEmpty(s) && GuidTools.GuidTryParse(s, out _);

Try / catch

try { return GuidTools.ParseGuid(input); }
catch (ArgumentException ex) { logger.Warn($"Bad GUID '{input}': {ex.InnerException?.Message}"); return Guid.Empty; }

Prevention

Always prefer GuidTryParse over the throwing parse for external input.
Trim and brace-strip input consistently before validation.
Log the original string from the inner exception when parse fails in batch jobs.

When it happens

Trigger: Passing a string that is not a valid GUID in any accepted form (N/D/B/P formats), e.g. "xyz", "12345", or a GUID with non-hex characters / wrong segment lengths, even after brace stripping.

Common situations: Parsing user-entered IDs, reading GUIDs from config/CSV where columns are misaligned, clipboard text with stray whitespace/punctuation, or a value extracted from inside braces that is still malformed.

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

AI-assisted analysis of BCUninstaller/Bulk-Crap-Uninstaller@608321de98 (2026-08-13). Data as JSON: /api/errors/f2023034b6b01fdb. Report an issue: GitHub.