C#无法更新数据库（SQlexpress）

#region Using directivesusing System;
using System.Data;            // Use ADO.NET namespace
using System.Data.SqlClient;  // Use SQL Server data provider namespace
using System.Collections.Generic;
using System.Text;#endregionnamespace UpdatingData
{
class Program
{
static void Main(string[] args)
{
// Specify SQL Server-specific connection string
SqlConnection thisConnection = new SqlConnection(
                @"Data Source=.\SQLEXPRESS;" +
                @"AttachDbFilename='C:\PROGRAM FILES\MICROSOFT SQL SERVER\MSSQL.1\MSSQL\DATA\NORTHWIND.MDF';" +
                @"Integrated Security=True;Connect Timeout=30;User Instance=true"); // Create DataAdapter object for update and other operations
SqlDataAdapter thisAdapter = new SqlDataAdapter(
 "SELECT CustomerID, CompanyName FROM Customers", thisConnection); // Create CommandBuilder object to build SQL commands
SqlCommandBuilder thisBuilder = new SqlCommandBuilder(thisAdapter);
// Create DataSet to contain related data tables, rows, and columns
DataSet thisDataSet = new DataSet(); // Fill DataSet using query defined previously for DataAdapter
thisAdapter.Fill(thisDataSet, "Customers"); // Show data before change
Console.WriteLine("name before change: {0}",
 thisDataSet.Tables["Customers"].Rows[9]["CompanyName"]); // Change data in Customers table, row 9, CompanyName column
thisDataSet.Tables["Customers"].Rows[9]["CompanyName"] = "Acme, Inc."; // Call Update command to  change in table
thisAdapter.Update(thisDataSet, "Customers");
                            //这里说数据库为只读            thisDataSet.Tables["Customers"].AcceptChanges(); Console.WriteLine("name after change: {0}",
 thisDataSet.Tables["Customers"].Rows[9]["CompanyName"]); thisConnection.Close();
Console.Write("Program finished, press Enter/Return to continue:");
Console.ReadLine();
}
}
}