***将连接字符串放在App.Config文件中

It will be better to put connection string in App.Config file

<appsettings>
    <connectionstrings>
        <add name="AccountingWindowApplication.Properties.Settings.WinPhoneAppConnectionString">
            connectionString="Data Source=COMPAQ-PC\SQLEXPRESS;Initial Catalog=WinPhoneApp;Integrated Security=True"
            providerName="System.Data.SqlClient" />
    </add></connectionstrings>  </appsettings>

并用作

and use as

SqlConnection cn = new SqlConnection();
       cn.ConnectionString = ConfigurationSettings.AppSettings["ConnectionString"].ToString();

         cn.Open();

希望能解决您的问题.
注意:将代码更改为Oledb

Hope it will solve your problem.
note:change code to Oledb

请参阅您的旧帖子......并查看评论...
祝你好运；

refer to you older post.......and see comments...
Best of luck;