Suddenly, the screen flashed green. A line of blue text appeared, overriding the error: > convert02:00:02_min_FIXED
# 4. Re‑assemble as a fixed‑width (6‑char) string # In many legacy systems the field must be left‑padded with zeros. fixed = category + subcategory + version # already 6 chars sone385engsub convert020002 min fixed
foreach (var ch in trimmed) if (!char.IsDigit(ch)) throw new ArgumentException("Input must consist of digits only.", nameof(input)); Suddenly, the screen flashed green