SqlConnection.BeginTransaction Method

Exception
Condition
SqlException
Parallel transactions are not allowed when using Multiple Active Result Sets (MARS).
InvalidOperationException
Parallel transactions are not supported.

private static void ExecuteSqlTransaction(string connectionString)
{
    using (SqlConnection connection = new SqlConnection(connectionString))
    {
        connection.Open();

        SqlCommand command = connection.CreateCommand();
        SqlTransaction transaction;

        // Start a local transaction.
        transaction = connection.BeginTransaction("SampleTransaction");

        // Must assign both transaction object and connection
        // to Command object for a pending local transaction
        command.Connection = connection;
        command.Transaction = transaction;

        try
        {
            command.CommandText =
                "Insert into Region (RegionID, RegionDescription) VALUES (100, 'Description')";
            command.ExecuteNonQuery();
            command.CommandText =
                "Insert into Region (RegionID, RegionDescription) VALUES (101, 'Description')";
            command.ExecuteNonQuery();

            // Attempt to commit the transaction.
            transaction.Commit();
            Console.WriteLine("Both records are written to database.");
        }
        catch (Exception ex)
        {
            Console.WriteLine("Commit Exception Type: {0}", ex.GetType());
            Console.WriteLine("  Message: {0}", ex.Message);

            // Attempt to roll back the transaction.
            try
            {
                transaction.Rollback();
            }
            catch (Exception ex2)
            {
                // This catch block will handle any errors that may have occurred
                // on the server that would cause the rollback to fail, such as
                // a closed connection.
                Console.WriteLine("Rollback Exception Type: {0}", ex2.GetType());
                Console.WriteLine("  Message: {0}", ex2.Message);
            }
        }
    }
}

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string save4 = "update CLIENT set RADD1='" + txtadd1.Text + "',RADD2='" + txtadd2.Text + "',RADD3='" + txtadd3.Text + "',RCITY='" + txtcity.Text + "',RPIN='" + txtpin.Text + "',RSTATE='" + txtstate.Text + "' where Applicant='" + txtName.Text + "' ";
            SqlCommand com4 = new SqlCommand(save4, con);

            string save5 = "update CLIENT set Possession='" + ddlpossession.SelectedValue + "',Occupy='" + ddlOqqupy.SelectedValue + "' where Applicant='" + txtName.Text + "'";
            SqlCommand com5 = new SqlCommand(save5, con);

            tr = con.BeginTransaction();
            com1.Transaction = tr;
            com2.Transaction = tr;

            com3.Transaction = tr;

            com4.Transaction = tr;
            com5.Transaction = tr;        
          
            com1.ExecuteNonQuery();
            com2.ExecuteNonQuery();
            com3.ExecuteNonQuery();
            com4.ExecuteNonQuery();
            com5.ExecuteNonQuery();