A Beginner's Tutorial for Understanding Transactions and TransactionScope in ADO.NET

using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Data.SqlClient;

public partial class _DefaultSql : System.Web.UI.Page 
{
    readonly string CONNECTION_STRING = ConfigurationManager.ConnectionStrings["SampleDbConnectionString1"].ConnectionString;
    
    protected void Page_Load(object sender, EventArgs e)
    {
        if (IsPostBack == false)
        {
            UpdateAmount();
        }        
    }

    protected void btnAccount1_Click(object sender, EventArgs e)
    {
        // Lets just hard code some values for demo purpose
        double amount = 0.0;
        double.TryParse(txtAmount.Text, out amount);

        PerformTransaction("2", "1", amount);
    }

    protected void btnAccount2_Click(object sender, EventArgs e)
    {   
        // Lets just hard code some values for demo purpose
        double amount = 0.0;
        double.TryParse(txtAmount.Text, out amount);

        PerformTransaction("1", "2", amount);
    }

    private void PerformTransaction(string creditAccountID, string debitAccountID, double amount)
    {        
        SqlConnection con = null;

        // they will be used to decide whether to commit or rollback the transaction
        bool result = false;
       
        string updateCommand = @"BEGIN TRY
                                    BEGIN TRANSACTION
                                        update Account set Amount = Amount - {0} where ID = {1}
                                        update Account set Amount = Amount + {2} where ID = {3}
                                    COMMIT TRANSACTION
                                END TRY
                                BEGIN CATCH
                                    ROLLBACK TRANSACTION
                                END CATCH";

        try
        {
            con = new SqlConnection(CONNECTION_STRING);
            con.Open();            

            // Let us do a debit first
            using (SqlCommand cmd = con.CreateCommand())
            {
                cmd.CommandType = CommandType.Text;
                cmd.CommandText = string.Format(updateCommand,                    
                    amount, debitAccountID,
                    amount, creditAccountID);

                // check if 2 records are effected or not
                result = cmd.ExecuteNonQuery() == 2;
            }
        }
        catch
        {
            
        }
        finally
        {
            con.Close();
        }

        UpdateAmount();
    }

    private void UpdateAmount()
    {
        // Lets show the updated balance to the user
        DataTable table = null;

        using (SqlConnection con = new SqlConnection(CONNECTION_STRING))
        {
            using (SqlCommand cmd = con.CreateCommand())
            {
                cmd.CommandType = CommandType.Text;
                cmd.CommandText = "select * from Account";

                try
                {
                    con.Open();
                    using (SqlDataAdapter da = new SqlDataAdapter(cmd))
                    {
                        table = new DataTable();
                        da.Fill(table);
                    }
                }
                catch (Exception ex)
                {
                    throw ex;
                }
            }
        }

        if (table != null)
        {
            GridView1.DataSource = table;
            GridView1.DataBind();
        }
    }
}