但未在用户代码中进行处理 具有固定名称“Oracle.ManagedDataAccess.Client”的 ADO.NET 提供程序未在计算机或应用程序配置文件中注册或无法加载。

这是使用ODP.NET链接Orcl数据库常见错误，需要配置系统环境变量。

解决方法如下：

找到以下路径文件：C:\Windows\Microsoft.NET\Framework\v4.0.30319\Config\machine.config

注意：修改前最好先备份以免....

将下面这段配置文件加入<configSections>节点下。

<configSections>
    <section name="oracle.unmanageddataaccess.client" type="OracleInternal.Common.CustomSectionHandler, Oracle.DataAccess, Version=4.121.2.0, Culture=neutral, PublicKeyToken=89b483f429c47342" />
    <section name="oracle.dataaccess.client" type="System.Data.Common.DbProviderConfigurationHandler, System.Data, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" />
    <section name="oracle.manageddataaccess.client" type="OracleInternal.Common.ODPMSectionHandler, Oracle.ManagedDataAccess, Version=4.121.2.0, Culture=neutral, PublicKeyToken=89b483f429c47342" />
    ................
    ................
</configSections>

　将以下配置加入<system.data>节点下

<system.data>
    <DbProviderFactories>
      <add name="ODP.NET, Unmanaged Driver" invariant="Oracle.DataAccess.Client" description="Oracle Data Provider for .NET, Unmanaged Driver" type="Oracle.DataAccess.Client.OracleClientFactory, Oracle.DataAccess, Version=4.121.2.0, Culture=neutral, PublicKeyToken=89b483f429c47342" />
      <add name="ODP.NET, Managed Driver" invariant="Oracle.ManagedDataAccess.Client" description="Oracle Data Provider for .NET, Managed Driver" type="Oracle.ManagedDataAccess.Client.OracleClientFactory, Oracle.ManagedDataAccess, Version=4.121.2.0, Culture=neutral, PublicKeyToken=89b483f429c47342" />
    </DbProviderFactories>
 </system.data>