[DotNetDevelopment] Deleting duplicates/Retaining data

[Nurul]

I need help with my programming,

   public void Add(DateTime dt, string Address, GpsPosition pos)
        {
            ListViewItem lvi = new ListViewItem(new string[]
{ dt.ToShortDateString(), Address, pos.Latitude.ToString("0.000000"),
pos.Longitude.ToString("0.000000") });
            this.lvPositionRequestLog.Items.Insert(0, lvi);

        }

I have this program that display my results in terms of date, address,
longtitude, latitude. But how do i delete my row/list if my result got
duplicate?

How do i retain my data in that row even when the program quits?