我在web.config文件中如下配置
<add name="ConnectionString" connectionString="Provider=MSDAORA.1;Data Source=ora817;User ID=db_bbs;Password=bbs;Unicode=True" providerName="System.Data.OleDb" />
访问时
string conString=ConfigurationManager.ConnectionStrings["connectionString"].ConnectionString;
OleDbConnection conn = new OleDbConnection(conString);
conn.Open(); ///一个 Oracle 错误，但无法从 Oracle 中检索错误信息。

OleDbDataAdapter datap = new OleDbDataAdapter("select * from TB_ADMIN", conn);
  data.Fill(ds,"TB_ADMIN");

<appSettings>
     <add key="..." value="..." />
</appSettings>
这样配置试试 读的时候用ConfigurationSettings.AppSettings[key];