It sounds like you will want to store your results in a List<t> as well as your ListView and then write the contents of the list out to a file. i.e.
List<string> resultData = new List<string>();
resultData.Add("Some result data");
etc...
using (StreamWriter writer = new StreamWriter("pathOfFileToSaveDataTo"))
{
for (int i = 0; i < resultData.Count; i++)
{
writer.WriteLine(resultData[i]);
}
writer.Close();
}
hope this helps.
EDIT:
You could also just write the contents of the ListView out to the file without storing the results in a List<T> if you wanted to.