TechnitiumSoftware/DnsServer · warning · ArgumentException

Group description length cannot exceed 255 characters.

Error message

Group description length cannot exceed 255 characters.

What it means

Thrown by the Group.Description setter when a non-whitespace value longer than 255 characters is supplied. Whitespace-only values are normalized to empty string, so only a genuinely long description triggers it. It is an ArgumentException enforcing the configured storage width.

Source

Thrown at DnsServerCore/Auth/Group.cs:134

                    case "dhcp administrators":
                        throw new InvalidOperationException("Access was denied.");

                    default:
                        _name = value;
                        break;
                }
            }
        }

        public string Description
        {
            get { return _description; }
            set
            {
                if (string.IsNullOrWhiteSpace(value))
                    _description = "";
                else if (value.Length > 255)
                    throw new ArgumentException("Group description length cannot exceed 255 characters.", nameof(Description));
                else
                    _description = value;
            }
        }

        #endregion
    }
}

View on GitHub (pinned to d0484b6c1e)

Solutions

1. Shorten the description to <= 255 characters.
2. Enforce a client-side maxlength and server-side validation on the description field.
3. Store longer prose in a separate notes/documentation attribute if available.

Example fix

// before
group.Description = description;

// after
if (!string.IsNullOrWhiteSpace(description) && description.Length > 255)
    description = description.Substring(0, 255);
group.Description = description;

if (!string.IsNullOrWhiteSpace(description) && description.Length > 255)
    description = description.Substring(0, 255);
group.Description = description;

try { group.Description = description; }
catch (ArgumentException ex) when (ex.ParamName == "Description")
{ return BadRequest(ex.Message); }

When it happens

Trigger: Assigning Group.Description = text where text is longer than 255 chars (and not whitespace-only).

Common situations: Pasting a long help/policy document into the description field; a UI without a maxlength; a migration that maps a verbose legacy field into Description.

Related errors

• Group name length cannot exceed 255 characters.
• The SSO Authority URL length cannot be more than 255 chars.
• The SSO Client ID length cannot be more than 255 chars.
• The SSO Client Secret length cannot be more than 255 chars.
• The SSO Metadata Address URL length cannot be more than 255

AI-assisted analysis of TechnitiumSoftware/DnsServer@d0484b6c1e (2026-08-13). Data as JSON: /api/errors/4a36f9230f73b4e6. Report an issue: GitHub.