記錄轉化爲有層次結構的樹狀列表的通用算法

轉載：http://www.cnblogs.com/ejiyuan/archive/2007/11/27/973765.html

 

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問題說明:	在獲取數據庫記錄數據的時候, 通常返回的ArrayList集合, 沒有了層次關係. 如果每次根據PID重新到數據庫獲取記錄, 可以做到, 但有以下幾個缺點: 1. 訪問數據庫記錄次數隨着記錄的增多而增多 2. 由於需要多次訪問數據庫, 因此訪問速度受影響 3. 需要數據庫訪問層的支持, 並對記錄進行轉化, 耦合性太強 4. 通用性不好, 每次需要一個新的類型列表, 就需要
解決方法:	我根據原有的樹狀結構算法代碼, 編寫一個通用的算法, 利用反射原理, 遞歸的對數據進行篩選. 這樣只需要訪問數據庫一次, 然後就在內存中遍歷, 而且適合於所有具有(PID, ID, Name)屬性的實體類集合的排序.   如我需要生成設備類型實體類集合的樹狀結構時候, 代碼如下:

 

ArrayList equipTypelist = equipmentType.GetAll(); equipTypelist = CollectionHelper.GetTreeItems(equipTypelist); this.ddlEquipmentTypes.DataSource = equipTypelist; this.ddlEquipmentTypes.DataTextField = "Name"; this.ddlEquipmentTypes.DataValueField = "ID"; this.ddlEquipmentTypes.DataBind(); this.ddlEquipmentType.Items.Insert(0, new ListItem("(全部)", "0"));

 

public class CollectionHelper { private static ArrayList Fill(int pID, int level, ArrayList list) { ArrayList returnList = new ArrayList(); foreach(object obj in list) { int typePID = (int)ReflectionUtil.GetProperty(obj, "PID"); int typeID = (int)ReflectionUtil.GetProperty(obj, "ID"); string typeName = ReflectionUtil.GetProperty(obj, "Name") as string; if(pID == typePID) { string newName = new string('-', level * 4) + typeName; ReflectionUtil.SetProperty(obj, "Name", newName); returnList.Add(obj); returnList.AddRange(Fill(typeID, level+1, list)); } } return returnList; } /**//// <summary> /// 生成有層次結構的列表 /// </summary> /// <param name="list">具有Name,ID,PID成員的任何集合</param> /// <returns></returns> public static ArrayList GetTreeItems(ArrayList list) { return Fill(-1, 0, list); } }

 

public sealed class ReflectionUtil { private ReflectionUtil() { } public static BindingFlags bf = BindingFlags.DeclaredOnly | BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance | BindingFlags.Static; public static void SetProperty(object obj, string name, object value) { PropertyInfo fi = obj.GetType().GetProperty(name, bf); fi.SetValue(obj, value,null); } public static object GetProperty(object obj, string name) { PropertyInfo fi = obj.GetType().GetProperty(name, bf); return fi.GetValue(obj,null); } }

 

 

效果圖如下