new to C#

I have created a form , with a working coding , but i need an extra assistance.

Somewhat , i am stuck on trying to figure out how to let the 3rd combobox value , determined by the first and second.

Like this :

Main Form

For the Main Category and Sub-Category , i have it working with this code.
This code also includes the 3rd ComboBox which operates without the first and second combobox.

public partial class User : Form
    {

        Dictionary<string, List<string>> Category = new Dictionary<string, List<string>>();

        DataSet ds1;

        public User()
        {
            InitializeComponent();
        }
        private void User_Load(object sender, EventArgs e)
        {

            SqlConnection conn = new SqlConnection();
            conn.ConnectionString = "Data Source=\\SQLEXPRESS;Initial Catalog=master;Integrated Security=True";
            conn.Open();

            SqlDataAdapter daMain = new SqlDataAdapter("SELECT * FROM MAINCATE", conn);
            ds1 = new DataSet();

            daMain.Fill(ds1, "Maincate");

            DataTable dt = ds1.Tables["MAINCATE"];
            foreach (DataRow dr in dt.Rows)
            {
                List<string> SubCats = new List<string> 
                {
                 dr["Subcat1"].ToString(), 
                 dr["Subcat2"].ToString(),
                 dr["Subcat3"].ToString(),
                 dr["Subcat4"].ToString()
                };
                Category.Add(dr["mainCate"].ToString(), SubCats);
                mainCatU.Items.Add(dr["mainCate"].ToString());
            }

            mainCatU.DropDownStyle = ComboBoxStyle.DropDownList;
            mainCatU.Enabled = true;
            subCatU.DropDownStyle = ComboBoxStyle.DropDownList;

//**Code for third combobox**

            SqlDataAdapter daSearch = new SqlDataAdapter("SELECT cName FROM ComDet", conn);
            DataTable dt1 = new DataTable();
            ListU.DataSource = dt1;
            daSearch.Fill(dt1);
            ListU.ValueMember = "cName";
            ListU.DisplayMember = "cName";
            ListU.DropDownStyle = ComboBoxStyle.DropDownList;
            ListU.Enabled = true;

//**----------------------**

            conn.Close();   
        }

        private void mainCatU_SelectedIndexChanged(object sender, EventArgs e)
        {
            if(Category.ContainsKey(mainCatU.SelectedItem.ToString()))
            {
                subCatU.DataSource = Category[mainCatU.SelectedItem.ToString()];
            }
        }

and the databases are as shown :

dbo.MAINCATE
MAINCATE

dbo.ComDet
ComDet

and the code for the View Selected Company button is :

private void searchBtn_Click(object sender, EventArgs e)
        {
            SqlConnection conn = new SqlConnection();
            conn.ConnectionString = "Data Source=PEWPEWDIEPIE\\SQLEXPRESS;Initial Catalog=master;Integrated Security=True";
            conn.Open();

            SqlDataAdapter daS = new SqlDataAdapter("select cName, cDetails, cDetails2 from ComDet where cName = @cName", conn);
            daS.SelectCommand.Parameters.Add("@cName", SqlDbType.VarChar).Value = ListU.SelectedValue;

            DataTable dts3 = new DataTable();
            daS.Fill(dts3);
            dataGridView1.DataSource = dts3.DefaultView;
            dataGridView1.SelectionMode = DataGridViewSelectionMode.FullRowSelect;

            conn.Close();

        }

so i wanted to do something like , getting the value of Main Category and Sub category to effect the list of the third combo box.

  • again , right now the third combo box is coded to run without the maincategory and subcategory
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