ho questo codice 
"      private void btnProsegui_Click(object sender, EventArgs e)
      {
          ArxCeClassTypeConfigurator form = new ArxCeClassTypeConfigurator(_database,AooArxCe,AooIXCe);
          form.ShowDialog();
      }"

"using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using static Azure.Core.HttpHeader;
using System.Windows.Forms;
using ImporterIxCe.Models;
using MongoDB.Driver;
using ImporterIxCe.Models.ArxCeModels;
using ImporterIxCe.Models.IXCeModels;
using Amazon.Runtime.Internal.Util;

namespace ImporterIxCe
{
    public partial class ArxCeClassTypeConfigurator : Form
    {
        List<ArxCeClassType> classTypeArxCe = new List<ArxCeClassType>();
        List<Label> classTypeArxCeLabels  = new List<Label>();
        List<ComboBox> comboBoxesClassTypeIXCe = new List<ComboBox>();

        public ArxCeClassTypeConfigurator(IMongoDatabase database, ArxCeAoo ArxCeAoo, IXCeAoo IXCeAoo)
        {
            try
            {
                InitializeComponent();
                if (ArxCeAoo != null)
                {
                    labelAooArxCe.Text = ArxCeAoo.Descrizione;
                }
                if (IXCeAoo != null)
                {
                labelAooIXCe.Text = IXCeAoo.Descrizione;

                }            

                LoadComboboxes();
            }
            catch (Exception ex)
            {
                Logging.Logger.Instance.Error(ex.Message);  
            }
        }

        private void LoadComboboxes()
        {
            const int combos = 6;
            for (int i = 0; i < combos; i++)
            {
                SplitContainer splitContainer = new SplitContainer
                {
                    Size = new System.Drawing.Size(400, 21), // Imposta la dimensione del SplitContainer
                    TabIndex = 0,
                    IsSplitterFixed = true // Rendi fisso il divisore per esempio
                };
                splitContainer.SplitterDistance = 100;

                SplitContainer splitComboButton = new SplitContainer
                {
                    Size = new System.Drawing.Size(300, 21), // Imposta la dimensione del SplitContainer
                    TabIndex = 0,
                    IsSplitterFixed = true // Rendi fisso il divisore per esempio
                };
                splitComboButton.SplitterDistance = 200;
                Label label = new Label();
                ArxCeClassType arxCeClassType = new ArxCeClassType();
                arxCeClassType.Id = i.ToString();
                arxCeClassType.Descrizione = "Descrizione" + i.ToString();
                label.Size = new System.Drawing.Size(90, 21); // Imposta la dimensione del ComboBox
                label.Text = arxCeClassType.Descrizione;
                classTypeArxCe.Add(arxCeClassType);
                classTypeArxCeLabels.Add(label);
                splitContainer.Panel1.Controls.Add(label);

                ComboBox comboBox2 = new ComboBox();
                comboBox2.Size = new System.Drawing.Size(190, 21);
                comboBox2.Items.Add(new IXCeClassType());
                //comboBoxesClassTypeIXCe.Add(comboBox2);
                //comboBoxesClassTypeIXCe[i].Size = new System.Drawing.Size(190, 21);
                //comboBoxesClassTypeIXCe[i].SelectedValueChanged += (object sender, EventArgs e) => { ComboBoxIxCe_Selection(sender, e, i); };

                //comboBoxesClassTypeIXCe[i].Items.Add(new IXCeClassType());









                //Button FieldConfiguration = new Button();
                //FieldConfiguration.Location = new Point(0, 0);
                //FieldConfiguration.Name = "FieldConfiguration";
                //FieldConfiguration.Size = new Size(90, 21);
                //FieldConfiguration.TabIndex = 0;
                //FieldConfiguration.Text = "Field Configuration";
                //FieldConfiguration.UseVisualStyleBackColor = true;
                //FieldConfiguration.Click += (object sender, EventArgs e) => { FieldConfiguration_Click(sender, e, i); };

                splitComboButton.Panel1.Controls.Add(comboBox2);
                //splitComboButton.Panel2.Controls.Add(FieldConfiguration);

                splitContainer.Panel2.Controls.Add(splitComboButton);

                flowLayoutCombos.Controls.Add(splitContainer);

            }

        }

        private void FieldConfiguration_Click(object sender, EventArgs e, int index)
        {


            ArxCeFieldConfigurator form = new ArxCeFieldConfigurator();
            form.ShowDialog();

        }

        private void ComboBoxIxCe_Selection(object sender, EventArgs e, int index)
        {
            if (comboBoxesClassTypeIXCe[index].SelectedItem is ArxCeAoo selectedAoo)
            {
               
            }


        }

    }
}
"

e mi sta staccando di questo errore al form.showDialog : 'Troppe voci nella casella combinata.'