ConnectionString 属性尚未初始化。

Question

为什么，我的.NET 2.0连接ACCESS数据库，发生ConnectionString 属性尚未初始化。 
<add key="access_con" value="Provider=Microsoft.Jet.OleDb.4.0;Data Source=|DataDirectory|\\wygl.mdb" ></add>
这个是连库代码

Answer 1

 
    public class PubConstant
    {        
        /// <summary>
        /// 获取连接字符串
        /// </summary>
        public static string ConnectionString
        {  
            
            get 
            {
                string _connectionString = ConfigurationManager.AppSettings["ConnectionString"];       
                string ConStringEncrypt = ConfigurationManager.AppSettings["ConStringEncrypt"];
                if (ConStringEncrypt == "true")
                {
                    _connectionString = DESEncrypt.Decrypt(_connectionString);
                }
                return _connectionString; 
            }
        }
这样的，动软生成的三层

Answer 2

参考configurationManager.connectionString["accessConnStr"].ToString()<connectionStrings> 
....
</connectionStrings>

Answer 3

string _connectionString = ConfigurationManager.AppSettings["access_con"]; 

Answer 4

提示 不支持关键字: “provider”。 ，怎么弄

Answer 5

看看我的方法吧， OleDbConnection conn;
        OleDbCommand comm = new OleDbCommand();        int NodesCunt = 0;//数据库中记录的条数        public static readonly string DBName = ConfigurationManager.AppSettings.Get("DBName").ToString();
        //从配置文件中得到数据库驱动 
        public static readonly string DBDriver = ConfigurationManager.AppSettings.Get("DBDriver").ToString();
        //得到数据库连接字符串 
        private static string Connection = DBDriver + DBName; 在到需要用的地方：
conn = new OleDbConnection(Connection);
           conn.Open();
            comm.Connection = conn;
在配置文件中：
<add key="DBDriver" value="Provider=Microsoft.Jet.OLEDB.4.0; Data Source ="/>
    <add key="DBName" value="C:\dvo_mdb\Nvss_data.mdb"/>