How to add references by automation

It's easy but I always forget the steps. I have to look in my code in order to remember. So here the steps:

1. Add a reference to VSLangProj. If you are writing a macro you don't need this step.
2. Add the using clause (C#)
            using VSLangProj; 

 3.    And use this function

  public bool AddReference(EnvDTE.Project project, string reference)
  {
      VSProject proj = m_Project.Object as VSProject;
      System.Diagnostics.Debug.Assert(proj != null); // This project is not a VSProject
      if (proj == null)
          return false;
      try
      {
          proj.References.Add(reference);
      }
      catch (Exception ex)
      {
          string message = String.Format("Could not add {0}. \n Exception: {1}", reference, ex.Message);
          System.Diagnostics.Trace.WriteLine(message);
          return false;
      }

      return true;
  }

In order to add a reference to a project you have to use proj.References.AddProject insted proj.References.Add.

If you wanna add a reference to an assembly that is in the GAC then pass just the dll name insted of the full path.