public enum VersionBaseType : System.Enum, System.IComparable, System.IConvertible, System.IFormattable, System.ISpanFormattable  

{
  // Must be called within QueuedTask.Run
  void ChangeVersions(Geodatabase geodatabase, string toVersionName)
  {
    using (VersionManager versionManager = geodatabase.GetVersionManager())
    {
      VersionBaseType versionBaseType = versionManager.GetCurrentVersionBaseType();

      if (versionBaseType == VersionBaseType.Version)
      {
        Version fromVersion = versionManager.GetCurrentVersion();
        Version toVersion = versionManager.GetVersion(toVersionName);

        // Switch between versions
        MapView.Active.Map.ChangeVersion(fromVersion, toVersion);
      }

      if (versionBaseType == VersionBaseType.HistoricalVersion)
      {
        HistoricalVersion fromHistoricalVersion = versionManager.GetCurrentHistoricalVersion();
        HistoricalVersion toHistoricalVersion = versionManager.GetHistoricalVersion(toVersionName);

        // Switch between historical versions
        MapView.Active.Map.ChangeVersion(fromHistoricalVersion, toHistoricalVersion);
      }

      // Switch from HistoricalVersion to Version and vice-versa 
      // MapView.Active.Map.ChangeVersion(fromHistoricalVersion, toVersion);
      // MapView.Active.Map.ChangeVersion(fromVersion, toHistoricalVersion);
    }
  }
}