I fixed it:
string[] apString = new string[lstvResults.Items.Count];
if (dlgExportFile.ShowDialog() == DialogResult.OK)
{
for (int i = 0; i < lstvResults.Items.Count-1; i++)
{
ListViewItem Col_Get = lstvResults.Items[i];
apString[i] = Col_Get.SubItems[2].Text;
}
}
string join = string.Join(",\n", apString);
join = join.TrimEnd('\r');
System.IO.File.WriteAllText(dlgExportFile.FileName, join);