ComboBox1.Perform(CB_SETDROPPEDWIDTH, 200, 0);
下拉高度
ComboBox1.DropDownCount:=20;
{$externalsym
cb_geteditsel}
cb_geteditsel = $0140;
{$externalsym
cb_limittext}
cb_limittext = $0141;
{$externalsym
cb_seteditsel}
cb_seteditsel = $0142;
{$externalsym
cb_addstring}
cb_addstring = $0143;
{$externalsym
cb_deletestring}
cb_deletestring = $0144;
{$externalsym
cb_dir}
cb_dir = $0145;
{$externalsym
cb_getcount}
cb_getcount = $0146;
{$externalsym
cb_getcursel}
cb_getcursel = $0147;
{$externalsym
cb_getlbtext}
cb_getlbtext = $0148;
{$externalsym
cb_getlbtextlen}
cb_getlbtextlen = $0149;
{$externalsym
cb_insertstring}
cb_insertstring = $014a;
{$externalsym
cb_resetcontent}
cb_resetcontent = $014b;
{$externalsym
cb_findstring}
cb_findstring = $014c;
{$externalsym
cb_selectstring}
cb_selectstring = $014d;
{$externalsym
cb_setcursel}
cb_setcursel = $014e;
{$externalsym
cb_showdropdown}
cb_showdropdown = $014f;
{$externalsym
cb_getitemdata}
cb_getitemdata = $0150;
{$externalsym
cb_setitemdata}
cb_setitemdata = $0151;
{$externalsym
cb_getdroppedcontrolrect}
cb_getdroppedcontrolrect = $0152;
{$externalsym
cb_setitemheight}
cb_setitemheight = $0153;
{$externalsym
cb_getitemheight}
cb_getitemheight = $0154;
{$externalsym
cb_setextendedui}
cb_setextendedui = $0155;
{$externalsym
cb_getextendedui}
cb_getextendedui = $0156;
{$externalsym
cb_getdroppedstate}
cb_getdroppedstate = $0157;
{$externalsym
cb_findstringexact}
cb_findstringexact = $0158;
{$externalsym
cb_setlocale}
cb_setlocale = 345;
{$externalsym
cb_getlocale}
cb_getlocale = 346;
{$externalsym
cb_gettopindex}
cb_gettopindex = 347;
{$externalsym
cb_settopindex}
cb_settopindex = 348;
{$externalsym
cb_gethorizontalextent}
cb_gethorizontalextent = 349;
{$externalsym
cb_sethorizontalextent}
cb_sethorizontalextent = 350;
{$externalsym
cb_getdroppedwidth}
cb_getdroppedwidth = 351;
{$externalsym
cb_setdroppedwidth}
cb_setdroppedwidth = 352;
{$externalsym
cb_initstorage}
cb_initstorage = 353;
{$externalsym
cb_msgmax}
cb_msgmax = 354;