app.config连接数据库的配置

原文：http://blog.sina.com.cn/s/blog_5deb89a701014hlx.html

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <connectionStrings>
    <add name="connString" connectionString="Data Source=.;database=Northwind;User ID=sa;Password="/>
  </connectionStrings>
</configuration>


在后台读取：
     SqlConnection conn = new SqlConnection();
            conn.ConnectionString = ConfigurationManager.ConnectionStrings["connString"].ConnectionString;
            conn.Open();
            string sql = "select * from Orders";
            SqlCommand cmd = new SqlCommand(sql, conn);
            SqlDataAdapter da = new SqlDataAdapter();
            da.SelectCommand = cmd;
            DataSet ds = new DataSet();
            da.Fill(ds);
            this.dataGridView1.DataSource = ds.Tables[0];
            conn.Close();


配置节:
1、这样配置的话
<connectionStrings>
    <add name="connString" connectionString="Data Source=.;Initial Catalog=Test;User ID=sa;Password=sasa"/>
</connectionStrings>
这样：
conn.ConnectionString = ConfigurationManager.ConnectionStrings["connString"].ConnectionString;

2、这样配置的话
<appSettings>
    <add key="connString" value="Data Source=.;Initial Catalog=Test;User ID=sa;Password=sasa;" />
</appSettings>
这样：
conn.ConnectionString = ConfigurationManager.AppSettings["connString"];