Allow to select only one item in a group at a time

To select only one item in a group at a time, use the ItemSelectionChangingEventArgs event. If more than one item in the same group gets selected, already selected item will be removed from ListView’s SelectedItems.

private void ListView_SelectionChanging(object sender, ItemSelectionChangingEventArgs e) 
{ 
  GroupResult actualGroup = null; 
  object key = null; 
  var selectedItems = listView.SelectedItems; 
  
  //To Cancel the Deselection 
  if (e.RemovedItems.Count > 0 && selectedItems.Contains(e.RemovedItems[0])) 
  { 
    e.Cancel = true; 
    return; 
  } 
  
 //To return when SelectedItems is zero 
  if (e.AddedItems.Count <= 0) 
     return; 
  
  var itemData = (e.AddedItems[0] as Contacts); 
  
  var descriptor = listView.DataSource.GroupDescriptors[0]; 
  if (descriptor.KeySelector == null) 
  { 
    var Collection = new PropertyInfoCollection(itemData.GetType()); 
    key = Collection.GetValue(itemData, descriptor.PropertyName); 
  } 
  else 
    key = descriptor.KeySelector(itemData); 
  
  for (int i = 0; i < listView.DataSource.Groups.Count; i++) 
  { 
   var group = listView.DataSource.Groups[i]; 
  
   if ((group.Key != null && group.Key.Equals(key)) || group.Key == key) 
   { 
     actualGroup = group; 
     break; 
   } 
} 
  
if (selectedItems.Count > 0) 
{ 
   foreach (var item in actualGroup.Items) 
    { 
      var groupItem = item; 
  
      if (selectedItems.Contains(groupItem)) 
      { 
        listView.SelectedItems.Remove(groupItem); 
        break; 
      } 
    } 
  } 
}

To know more about Selection, please refer our documentation here