scan.cs

public static class PropertyNameDataCollector
{
    public static async Task Scan(this Assembly assembly, string outputFilePath, bool includeHeader = true)
    {
        var properties = assembly
            .GetTypes()
            .SelectMany(x => x.GetProperties())
            // only want BCL types
            .Where(x => x.PropertyType.Namespace != null && x.PropertyType.Namespace.StartsWith("System"))
            .Select(x => new
            {
                x.Name,
                Type = x.PropertyType.IsGenericType 
                    ? x.PropertyType.GetGenericTypeDefinition().FullName
                    : x.PropertyType.FullName,
            });

        var csv = new StringBuilder();
        if (includeHeader)
        {
            csv.AppendLine("Name,Type");
        }

        foreach (var property in properties) {
            var row = $"{property.Name},{property.Type}";
            Console.WriteLine($"- {row}");
            csv.AppendLine(row);
        }
        
        await File.AppendAllTextAsync(outputFilePath, 
            csv.ToString(), 
            Encoding.UTF8
        );
    }
}