Could not load file or assembly 'Interop.ADODB, Version=6.0.0.0, Culture=neutral解决办法

Could not load file or assembly 'Interop.ADODB, Version=6.0.0.0, Culture=neutral
错误：Could not load file or assembly 'Interop.ADODB, Version=6.0.0.0, Culture=neutral, PublicKeyToken=null' or one of its dependencies. The system cannot find the file specified.



  CDO.Message msg = new CDO.MessageClass();
  CDO.Configuration c = new CDO.ConfigurationClass();
  msg.Configuration = c;
  msg.CreateMHTMLBody("http://baidu/erererere.htm", CdoMHTMLFlags.cdoSuppressAll, "123", "123");
  msg.GetStream().SaveToFile(@"C:\file\file.htn" , ADODB.SaveOptionsEnum.adSaveCreateOverWrite);
  b = true;

以上是我代码的使用，我之前是这么用的没有问题。现在不能用了。是跟我framework的版本有关吗？是不是我要下载新一点儿的Dll。从哪儿下载？

------解决方案--------------------
缺少引用