C#

void diaryListView_MouseUp(object sender, MouseEventArgs e)
        {
            int selectedSubItem =
            this.GetSubItem(this.diaryListView, new Point(e.X, e.Y));
            if (selectedSubItem != -1)
            {
                
                    ListViewItem lvItem = diaryListView.SelectedItems[0]; *** FAILS HERE ***
                    var file = lvItem.SubItems[14].Text.ToString();
                        if (selectedSubItem == 0 & lvItem.SubItems[14].Text.ToString().Length > 0)
                        {

                            viewFile(file);
                        }
                
            }
        }
        
        public struct RECT
	        {
	            public int Left;
	            public int Top;
	            public int Right;
	            public int Bottom;
	        }
	        [DllImport("user32.dll")]
	        private extern static int SendMessage(
	           IntPtr hWnd, int wMsg, int wParam, ref RECT lParam);
	
	        /// <summary>
	        /// Return -1 if invalid subitem clicked otherwise return index
	        /// of clicked subitem (zero based)
	        ///
	        ///
	        ///
	        /// <returns>int
	        /// <remarks>
	        public int GetSubItem(ListView lv, Point pt)
	      {
	         const int LVM_FIRST = 0X1000;
	         const int LVM_GETSUBITEMRECT = LVM_FIRST + 56;
	         const int LVIR_BOUNDS = 0;
	         ListViewItem.ListViewSubItem subItem = null;
	         int subItemIDX = -1;
	         RECT lviRect;
	         ListViewItem lvi = lv.GetItemAt(pt.X, pt.Y);
	
	         if (lvi == null && lv.SelectedItems.Count > 0)
	            lvi = lv.SelectedItems[0];
	
	         if (lvi != null)
	         {
	            int sendMessageVal = 0;
	
	            for (int i = 1; i < lvi.SubItems.Count; i++)             {
	               subItem = lvi.SubItems[i];
	               lviRect = new RECT();
	               lviRect.Top = i;
	               lviRect.Left = LVIR_BOUNDS;
	               sendMessageVal =
	                  SendMessage(lv.Handle,
	                  LVM_GETSUBITEMRECT,
	                  lvi.Index,
	                  ref lviRect);
	               if (pt.X < lviRect.Left)
	               {
	                  subItem = lvi.SubItems[0];
	                  subItemIDX = 0;
	                  break;
	               }
	               else if (pt.X >= lviRect.Left & pt.X <= lviRect.Right)                {
	                  subItemIDX = i;
	                  break;
	               }
	               else
	                  subItem = null;
	            }
	         }
	         if (subItem == null || lvi == null)
	            subItemIDX = -1;
	         return subItemIDX;
      }</remarks></returns></summary>

private void viewFiles_CellMouseClick(object sender, DataGridViewCellMouseEventArgs e)
{
  if (e.Button == MouseButtons.Right)
  {
    // Here we need to clear the selection!..
    viewSessions.Rows[e.RowIndex].Selected = true;
  }
}