Check if SPLIst exist

static bool ListExists(SPWeb web, string listName)
{
return web.Lists.Cast().Any(list => string.Equals(list.Title, listName));
}


static bool WebExists(SPSite site, string webName)
{
return site.AllWebs.Cast().Any(web => string.Equals(web.Name, webName));
}

http://whatsthesharepoint.com/2010/01/easy-check-if-an-spwebsplist-exist/