This code will restore all the items deleted from the specified list:
string listUrl = "web/relative/list/url"; // without leading slash!
var toRestore = new List<SPRecycleBinItem>();
foreach (SPRecycleBinItem recycleBinItem in web.RecycleBin)
{
if (recycleBinItem.ItemType == SPRecycleBinItemType.ListItem
&& recycleBinItem.DirName.ToLowerInvariant() == listUrl.ToLowerInvariant())
{
toRestore.Add(recycleBinItem);
}
}
foreach (var itemToRestore in toRestore)
{
itemToRestore.Restore();
}
Note: this code will require elevated privilegies, if you want to allow ordinary portal users to use it.