Fix IP scanner export NullReferenceException and CSV format bug

[Copilot]

Changes proposed in this pull request

• Fixed missing comma separator in CSV export after Bytes field causing malformed output (header: BytesPortStatus → Bytes,PortStatus)
• Added null checks for PingInfo, Ports, and NetBIOSInfo properties to prevent NullReferenceException across all export formats (CSV, XML, JSON)
• Optimized JSON and XML exports: use Array.Empty<object>() and Enumerable.Empty<XElement>() instead of allocating empty arrays or returning null

Related issue(s)

• Fixes ip scanner can't export to file #2951

Copilot generated summary

Copilot summary

The export methods in ExportManager.IPScannerHostInfo.cs were failing with NullReferenceException when encountering scan results with null collections or properties. The CSV export also had a formatting bug where the Bytes field lacked a comma separator, causing column misalignment.

CSV Export (CreateCsv):

// Before: Missing comma after Bytes
$"{info.PingInfo.Bytes}" + $"{(info.IsAnyPortOpen ? ...)}"

// After: Comma added, null checks applied
if (info?.PingInfo == null) continue;
if (info.Ports != null) { /* iterate ports */ }
$"{info.PingInfo.Bytes}," + $"{(info.IsAnyPortOpen ? ...)}"
$"{info.NetBIOSInfo?.IsReachable},"  // Null-conditional operators

XML Export (CreateXml):

// Before: No null filtering or handling
from info in collection select new XElement(...)
from port in info.Ports select ...  // NullReferenceException if Ports is null

// After: Filter nulls, return empty enumerable
from info in collection
where info?.PingInfo != null
select new XElement(...,
    info.Ports != null 
        ? from port in info.Ports select ...
        : Enumerable.Empty<XElement>()
)

JSON Export (CreateJson):

// Before: No filtering, inefficient array allocation
var jsonData = new object[collection.Count];
var jsonDataPorts = new object[collection[i].Ports.Count];  // Throws if Ports is null

// After: Pre-filter, conditional allocation
var validCollection = collection.Where(info => info?.PingInfo != null).ToList();
object[] jsonDataPorts = info.Ports != null && info.Ports.Count > 0
    ? new object[info.Ports.Count]
    : Array.Empty<object>();

All export methods now handle null properties defensively while maintaining data integrity.

To-Do

• Update documentation to reflect this changes
• Update changelog to reflect this changes

Contributing

By submitting this pull request, I confirm the following:

• I have read and understood the contributing guidelines and the code of conduct.
• I have have added my name, username or email to the contributors list or don't want to.
• The code or resource is compatible with the GNU General Public License v3.0.

Original prompt

Can you check this issue #2951 and find possible issues in the logic.

I assume it's in the following files:

https://github.com/BornToBeRoot/NETworkManager/blob/main/Source/NETworkManager.Models/Export/ExportManager.IPScannerHostInfo.cs

https://github.com/BornToBeRoot/NETworkManager/blob/main/Source/NETworkManager/ViewModels/IPScannerViewModel.cs

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