Keeping only one group in expanded state

To keep any one specific group alone in the expanded state, use the SfListView.GroupExpanding event. The particular selected group can be get from GroupExpandCollapseChangingEventArgs, by which you can compare and collapse all other groups, and expand the particular selected group.

private void ListView_GroupExpanding(object sender, GroupExpandCollapseChangingEventArgs e) 
{ 
  if (e.Groups.Count > 0) 
  { 
    var group = e.Groups[0]; 
    if (expandedGroup == null || group.Key != expandedGroup.Key) 
    { 
      foreach (var otherGroup in listView.DataSource.Groups) 
      { 
        if (group.Key != otherGroup.Key) 
        { 
          listView.CollapseGroup(otherGroup); 
        } 
      } 
      expandedGroup = group; 
      listView.ExpandGroup(expandedGroup); 
    } 
 } 
}

To know more about grouping, please refer our documentation here