BornToBeRoot/NETworkManager · error · Exception

message (joined PowerShell error streams)

Error message

message (joined PowerShell error streams)

What it means

ThrowOnError inspects ps.Streams.Error after running NetNeighbor PowerShell commands (New-/Remove-NetNeighbor, or clearing the table). If any error records exist, they are joined with Environment.NewLine, logged as a warning, and thrown as a generic Exception carrying the full PowerShell error text.

Solutions

  1. Run the application elevated; NetNeighbor cmdlets require administrator rights.
  2. Validate the IP address and physical (MAC) address format before calling AddEntryAsync.
  3. For deletes, check the entry exists first or tolerate 'not found' errors by parsing the message.
  4. Catch the exception and show the multi-line PowerShell error to the user; it names the failing cmdlet and parameter.

Example fix

// before
await NeighborTable.AddEntryAsync(new NeighborTableEntryInfo { IPAddress = ip, PhysicalAddress = mac, ... }); // throws on bad input
// after
if (!System.Net.IPAddress.TryParse(ip, out _) || !System.Net.NetworkInformation.PhysicalAddress.Parse(mac.Replace('-', ':'))...)
    throw new ArgumentException("Invalid IP or MAC address");
await NeighborTable.AddEntryAsync(entry);
Defensive patterns

Strategy: validation

Validate before calling

null

Type guard

static bool IsValidNeighborEntry(NeighborTableEntryInfo e) => e != null && e.IPAddress != null && e.PhysicalAddress != null && !e.PhysicalAddress.Equals(System.Net.NetworkInformation.PhysicalAddress.None) && e.InterfaceIndex > 0;

Try / catch

try
{
    await NeighborTable.AddEntryAsync(entry);
}
catch (Exception ex) when (ex.Message.Contains("already exists") || ex.Message.Contains("Failed"))
{
    Log.Warn($"NetNeighbor error: {ex.Message}");
    // show the multi-line PowerShell error to the user
}

Prevention

When it happens

Trigger: AddEntryAsync with an invalid IP/MAC or an entry already present; DeleteEntryAsync for a neighbor that does not exist; DeleteTableAsync when entries cannot be removed (in-use or permission issues); running without elevation so NetNeighbor cmdlets are denied.

Common situations: Non-admin execution (NetNeighbor requires elevation); duplicate static ARP entries; malformed MAC address strings; interface index/IPAddress not matching an existing interface.

Related errors

AI-assisted analysis of BornToBeRoot/NETworkManager@2780d65469 (2026-09-12). Data as JSON: /api/errors/21e2c5e11f61939c. Report an issue: GitHub.

Appendix: source

Thrown at Source/NETworkManager.Models/Network/NeighborTable.cs:407

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    /// <summary>
    /// Throws an <see cref="Exception"/> whose message is the joined PowerShell error
    /// stream when <paramref name="ps"/> reported one or more errors.
    /// </summary>
    private static void ThrowOnError(SMA.PowerShell ps)
    {
        if (ps.Streams.Error.Count == 0)
            return;

        var message = string.Join(Environment.NewLine, ps.Streams.Error);

        Log.Warn($"PowerShell error: {message}");

        throw new Exception(message);
    }

    #endregion
}

View on GitHub (pinned to 2780d65469)