The easiest would be using a foreach:
foreach(GridViewRow row in GridView2.Rows)
{
// here you'll get all rows with RowType=DataRow
// others like Header are omitted in a foreach
}
Edit: According to your edits, you are accessing the column incorrectly, you should start with 0:
foreach(GridViewRow row in GridView2.Rows)
{
for(int i = 0; i < GridView2.Columns.Count; i++)
{
String header = GridView2.Columns[i].HeaderText;
String cellText = row.Cells[i].Text;
}
}