Convert this code from C# to VB

public string GetGroups()
{
  DirectorySearcher search = new DirectorySearcher(_path);
  search.Filter = "(cn=" + _filterAttribute + ")";
  search.PropertiesToLoad.Add("memberOf");
  StringBuilder groupNames = new StringBuilder();
  try
  {
    SearchResult result = search.FindOne();
    int propertyCount = result.Properties["memberOf"].Count;
    String dn;
    int equalsIndex, commaIndex;

    for( int propertyCounter = 0; propertyCounter < propertyCount;
         propertyCounter++)
    {
      dn = (String)result.Properties["memberOf"][propertyCounter];

      equalsIndex = dn.IndexOf("=", 1);
      commaIndex = dn.IndexOf(",", 1);
      if (-1 == equalsIndex)
      {
        return null;
      }
      groupNames.Append(dn.Substring((equalsIndex + 1),
                        (commaIndex - equalsIndex) - 1));
      groupNames.Append("|");
    }
  }
  catch(Exception ex)
  {
    throw new Exception("Error obtaining group names. " +
      ex.Message);
  }
  return groupNames.ToString();
}