Index was out of range. Must be non-negative and less than the size of the collection.

could please help me to find a solution?
I am trying to fill in the flowlayoutpanel1 with 9 items associated with an  event.  I'm using next and previous buttons to navigate through it, but when I click the previous button I face index was out of range problem with clicking one of the items as well flowlayoutpanel1 decreased to 6 items:

private void frmelection_Load(object sender, EventArgs e)
       {
           Cards = new List<Candidate>();
           btnprevious.Enabled = false;
           
           var cand = cancontroller.GetAllCandidates();
           if (cand.Count() <= 9)
           {
               btnnext.Enabled = false;
           }
           foreach (var i in cand)
           {
               Cards.Add(new Candidate{
                   ID=i.ID,
                   name=i.name,
                   candidatepic=i.candidatepic,
                   logoID=i.logoID
               });             
           }
   
           for (int i = 0; i < 9; i++)
           {
               //Check if Cards Has the Index
   
               if (Cards.Count - 1 < i)
                   break;
               indexer++;
               Candpanel c = new Candpanel();
               c.Controls.Add(addlblID(Cards[i].ID));
               c.Controls.Add(addlblName(Cards[i].name));
               c.Controls.Add(addpic(Cards[i]));
               flowLayoutPanel1.Controls.Add(c);
               c.DoubleClick += new EventHandler((s, ee) => this.CandpanelDoubleClick(s, e, Cards[i]));
           }
       }

       private void btnprevious_Click(object sender, EventArgs e)
       {
           FLPContainer.Controls.Clear();
           btnnext.Enabled = true;
           var index = indexer - 9;
   
           try
           {
               for (int i = index; i >= 0; i--)
               {
                   //Check if Cards Has the Index
                   if (Cards.Count - 1 < i)
                       break;
   
                   // Preventing User From Going Forward Case the List is Back Default
                   if (i == 9)
                       btnprevious.Enabled = false;
   
                   indexer++;
                   var c = new Candpanel();
                   c.Controls.Add(addlblID(Cards[i].ID));
                   c.Controls.Add(addlblName(Cards[i].name));
                   c.Controls.Add(addpic(Cards[i]));
                   c.DoubleClick += new EventHandler((s, ee) => this.CandpanelDoubleClick(s, e, Cards[i]));
                   flowLayoutPanel1.Controls.Add(c);
               }
           }
           catch
           {
               return;
           }
       }