Single Tier 2-Tier and 3-Tier Architecture in C#

Question

Sir, I became tired of searching the .net architecture examples in web.

I need your help in giving the link to see the .net architecture with examples.

See the code below:-


 protected SqlConnection sqlCon;
        public frmRejectionIn()
        {
            InitializeComponent();
 sqlCon = new SqlConnection(constring);
        }

public void CashpartyComboFill()
        {
            try
            {
                if(sqlCon.State==ConnectionState.Closed)
                {
                    sqlCon.Open();
                }
                DataTable d = new DataTable();
                SqlDataAdapter da = new SqlDataAdapter("select * from tbl_AccountGroup", sqlCon);
                da.Fill(d);
                cmbcashorParty.DataSource = d;
                cmbcashorParty.DisplayMember = "ledgerName";
                cmbcashorParty.ValueMember = "ledgerId";

               
            }
            catch (FileIoException)
            {
                throw;
            }
            
        }


please tell me which architecture this code represent?

could you give me the link to learn the difference between all types of architecture in .net with examples?