public HistoricalVersion GetCurrentHistoricalVersion()

public 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);

  }
}