APP.config配置如下：

主要是数据库操作：

方法一：         string _connectionString = System.Configuration.ConfigurationManager.ConnectionStrings["strCon"].ToString();

方法二：                string _connectionString = ConfigurationManager.AppSettings["ConnectionString"];

在后台读取：

SqlConnection conn = new

SqlConnection();

conn.ConnectionString =

ConfigurationManager.ConnectionStrings["strCon"].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();