C#

foreach (Person person in personList)
{
  ListViewItem lvi = new ListViewItem(person.Name); // sets the text of the main (leftmost) column
  lvi.Tag = person.Id; // no need for conversion, .Tag is of type object
  lvi.SubItems.Add(person.Age.ToString());
  listView1.Items.Add(lvi);
}

public ListViewItem ToListViewItem()
{
    ListViewItem result = new ListViewItem(Name); // using name here saves you creating the item for the first column!
    result.Tag = this;
    result.SubItems.Add(Age.ToString());
    return result;
}

foreach (Person person in personList)
{
    listView1.Items.Add(person.ToListViewItem());
}

Person selectedPerson = (Person)listView.Items[itemIndex].Tag;
// ID is available in selectedPerson.ID

Quake2Player wrote:

Is it ok to return a ListView

// DO NOT do this!
public void AddToListView(ListView listView)
{
    ListViewItem listViewItem = new ListViewItem(Name);
    // ...
    listView.Items.Add(listViewItem);
}

public override string ToString()
{
    return string.Format("Name: {0}, Age: {1}", Name, Age);
}

J4amieC wrote:

Your database should not be responsible for formatting anything, least of all Dates.

DateTime visitDate = (DateTime)row["VisitDate"];

txtVisDay.Text = visitDate.Day.ToString();