C# 方法返回未知长度数组

#region 获取根菜单ID
private string[] GetRootMenuID(string userName)
{
SPList userBlockList = web.Lists[SysConst.T_UserBlock];
var qList = (from SPListItem userblock in userBlockList.Items where userblock.GetStringValue("UserAD").Equals(userName) select new { MenuID = userblock.GetStringValue("RootMenuID") }).Distinct();

System.Collections.ArrayList list = new System.Collections.ArrayList();
if (qList != null)
{
foreach (var q in qList)
{
list.Add(q.MenuID);
}
}

return (string[])list.ToArray(typeof(string));
}
#endregion