private void LoadOldSymbols(ICompositeSymbol symbol)
 {
     if (symbol == null || symbol.Symbols == null || symbol.Symbols.Count == 0)
     {
         return;
     }
     foreach (ISymbol sym in symbol.Symbols)
     {
         listBox1.Items.Add(new SymbolNamePair(sym, "符号(" + _idx.ToString() + ")"));
         _idx++;
     }
 }
        protected override IFeatureRenderer Apply()
        {
            ICompositeSymbol sym = (_layer.Renderer as SimpleFeatureRenderer).Symbol as ICompositeSymbol;

            if (listBox1.Items.Count > 0)
            {
                if (sym == null)
                {
                    sym = new CompositeSymbol();
                }
                else
                {
                    sym.Symbols.Clear();
                }
                foreach (SymbolNamePair p in listBox1.Items)
                {
                    sym.Symbols.Add(p.Symbol);
                }
            }
            return(_layer.Renderer);
        }