对象引用未设置为我的代码中的对象实例请帮助我

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

namespace AllQueryRun
{
    class Program
    {
        static void Main(string[] args)
        {
            //1: Specify SQL Server connection string
            SqlConnection con =new SqlConnection("Data Source=(local);Initial Catalog=migrationtest; Trusted_Connection=True");

        //  SqlConnection con = new SqlConnection(@"Data  Source =.\SQLEXPRESS;"+@"AttachDbFilename=?C:\SQL Server 2000 Sample Databases\NORTHWIND.MDF?;" +@"Integrated Security=True;Connect Timeout=30;User Instance=true" );

          //2: Create DataAdapter object

            SqlDataAdapter da = new SqlDataAdapter("Select TEMPLATEID,TEMPLATENAME,DESCRIPTION from TemplateMaster", con);

          //3: Create DataSet object to contain  data tables, rows, and columns

          DataSet ds = new DataSet();

         //4: Fill DataSet using query defined for DataAdapter

          da.Fill(ds,"TemplateMaster details");

         //5:Access data row wise using foreach loop

          foreach (DataRow dr in ds.Tables["TemplateMaster"].Rows)

         {

             Console.WriteLine(dr["TEMPLATEID"] + "\t" + dr["TEMPLATENAME"]);
             

         }

         //Closing the connection

         con.Close();
         Console.Write("Program finished, press Enter/Return to continue:");

         Console.ReadLine();

        }
    }
}

i得到的对象引用未设置为对象的实例，其中错误是每个都是okey

i got object reference not set to an instance of an object where is error every thing is okey