get family symbol revit api

                                    public Result Execute( 
  ExternalCommandData commandData,
  ref string message,
  ElementSet elements )
{
  UIApplication uiapp = commandData.Application;
  Document doc = uiapp.ActiveUIDocument.Document;
 
  Stopwatch sw = Stopwatch.StartNew();
 
  XElement xmlFamilyInstances = new XElement( 
    "Family_Inventory" );
 
  // retrieve all families. 
  // use the ElementClassFilter shortcut 
  // and filter all "Family" elements.
 
  FilteredElementCollector families 
    = new FilteredElementCollector( doc );
 
  families.OfClass( typeof( Family ) );
 
  int nFamily = 0;
  int nSymbol = 0;
  int nInstance= 0;
 
  foreach( Family family in families )
  {
    ++nFamily;
 
    // XML: Start by adding the Family element
 
    XElement temp = new XElement( 
      "FamilyName", family.Name );
 
    // use the FamilySymbolFilter for each Family
 
    FamilySymbolFilter filterFamSym 
      = new FamilySymbolFilter( family.Id );
 
    FilteredElementCollector famSymbols 
      = new FilteredElementCollector( doc );
 
    famSymbols.WherePasses( filterFamSym );
 
    foreach( FamilySymbol famSymbol in famSymbols )
    {
      ++nSymbol;
 
      FamilyInstanceFilter filterFamilyInst 
        = new FamilyInstanceFilter( 
          doc, famSymbol.Id );
 
      FilteredElementCollector collectorFamInstances 
        = new FilteredElementCollector( 
          doc, doc.ActiveView.Id );
 
      IEnumerable<FamilyInstance> famInstances 
        = collectorFamInstances
          .WherePasses( filterFamilyInst )
          .OfType<FamilyInstance>();
 
      int nInstanceCount 
        = famInstances.Count<FamilyInstance>();
 
      nInstance += nInstanceCount;
 
      temp.Add( new XElement( 
        "SymbolName", 
        famSymbol.Name,
        from fi in famInstances
          select new XElement( 
            "Instance", 
            fi.Id.ToString(),
            new XElement( "Type", 
              fi.GetType().ToString() ),
            new XElement( "Position", 
              LocationString( fi ) ) ) ) );
    }
    xmlFamilyInstances.Add( temp );
  }
 
  // Create the XML report document
 
  XDocument xmldoc =
    new XDocument(
        new XDeclaration( "1.0", "utf-8", "yes" ),
        new XComment( 
          "Current Family Inventory of Revit project: "
          + doc.PathName ),
        xmlFamilyInstances );
 
  string fileName = "C:/FamilyInventory.xml";
  xmldoc.Save( fileName );
 
  Util.ShowElapsedTime( sw,
    "Linq Example 3 XML Report",
    string.Format( "{0} families with {1} symbols and {2} instances",
      nFamily, nSymbol, nInstance ),
    string.Empty );
 
  // We can use Internet Explorer or whatever 
  // your favorite XML viewer is...
  Process.Start(
    "C:/Program Files/Internet Explorer/iexplore.exe", 
    fileName);
 
  // Here is one that is free and is a little more 
  // robust than Internet Explorer. If interested, 
  // download from here: 
  // http://download.cnet.com/XML-Marker/3000-7241_4-10202365.html
  //Process.Start( @"C:/Program Files (x86)/XML Marker/xmlmarker.exe", fileName );
 
  return Result.Succeeded;
}