sql 参数化查询，添加，删除

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data;
using System.Data.SqlClient;


namespace ConsoleApplication10
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Test");
            string fname = "zhuobin";
            string lname = "bin";
            SqlParameter firstName;
            SqlParameter lastName;
            SqlConnection conn = new SqlConnection("Data source=zhuobin;uid=sa;pwd=zhuobin;database=northwind");
            string sqlqry = @"select count(*)  from employees";
            string sqlInsert = @"insert into employees(firstname,lastname)values(@fname,@lname)";
            string sqldel = @"delete from employees where firstname=@fname and lastname=@lname";
            SqlCommand cmdQry = new SqlCommand(sqlqry,conn);
            SqlCommand cmdNon = new SqlCommand(sqlInsert,conn);
            
            try
            {
                conn.Open();
                Console.WriteLine("Before insert the number of tthe employees is {0}",cmdQry.ExecuteScalar());
                firstName = new SqlParameter();
                firstName.ParameterName = "@fname";
                firstName.SqlDbType = SqlDbType.VarChar;
                firstName.Size = 10;
                firstName.Value = fname;
                lastName = new SqlParameter();
                lastName.ParameterName = "@lname";
                lastName.SqlDbType = SqlDbType.VarChar;
                lastName.Size = 10;
                lastName.Value = lname;
                cmdNon.Parameters.Add(firstName);
                cmdNon.Parameters.Add(lastName);
               // cmdNon.Parameters["fname"].Value = fname;
               // cmdNon.Parameters["lname"].Value = lname;
                Console.WriteLine("Execute statement:{0}",cmdNon.CommandText);
                cmdNon.ExecuteNonQuery();
                Console.WriteLine("After the insert the number of the employees is {0}",cmdQry.ExecuteScalar().ToString());
                cmdNon.CommandText=sqldel;
                Console.WriteLine("execute statement :{0}",cmdNon.CommandText);
                cmdNon.ExecuteNonQuery();
                Console.WriteLine("After the delete ,the number of the employees is {0}",cmdQry.ExecuteScalar().ToString());

            }
            catch (SqlException ex)
            {
                Console.WriteLine("Error:" + ex.Message);
            }
            finally
            {
                conn.Close();
            }
            Console.ReadLine();
        }
    }
}