<add name="access1" connectionString="Provider=Microsoft.Jet.OleDb.4.0;Data Source="/>
        <add name="access2" connectionString="~/App_Data/#Address.mdb"/>

------解决方案--------------------

C# code

private static string _AccessConnStr = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + System.AppDomain.CurrentDomain.BaseDirectory.ToString() + @"\Data\Data.mdb;Jet OLEDB:Database Password=ybllz!@#402719";
  /// <summary>
        /// 执行SQl语句,如果执行成功则返回为真
        /// </summary>
        /// <param name="Sql">一条可执行的SQL语句</param>
        /// <returns>返回一个布尔值,执行成功返回 true,否则返回false</returns>
        /// 
        private Boolean ExecSql(string Sql)
        {
            OleDbConnection Myconn = new OleDbConnection();
            OleDbCommand Mycmd = Myconn.CreateCommand();
            Boolean RetVal = false;
            try
            {
                Myconn.ConnectionString = _AccessConnStr;
                Myconn.Open();
                Mycmd.CommandText = Sql;
                Mycmd.CommandType = System.Data.CommandType.Text;

                Mycmd.ExecuteNonQuery();
                Mycmd.Dispose();

                Myconn.Close();
                Myconn.Dispose();

                RetVal = true;
            }
            catch (Exception)
            {
                Mycmd.Dispose();
                if (Myconn.State == ConnectionState.Open) { Myconn.Close(); }
                Myconn.Dispose();
            }
            return RetVal;
        }

------解决方案--------------------
数据库是否存在问题
用字符串连接数据看看  
<add name="accessConnStr" connectionString="Provider=Microsoft.Jet.OLEDB.4.0; Data Source= |DataDirectory|a.mdb" providerName="System.Data.OleDb"/>  

<appSettings>  
<add key="ConnString" value="provider=microsoft.jet.oledb.4.0;data source="/>  
<add key="dbPath" value="~/App_Data/a.mdb"/>  
</appSettings>