在项目中，时常会遇到存在上下级关系的数据。在呈现方面，按照传统方法，不得不组装TreeNode之后添加到TreeView 中，已实现树形数据的显示。如果项目中需要多处使用树，毫无疑问这将存在巨大的代码冗余，会有无数针对不同实体组件TreeNode的代码出现，整体风格糟糕至极。

　　在近期的项目中，很多地方拥有这样的上下级关系，如下图所示，可以清楚的看出它们直接的关系

　　在数据的查询上，一般对于Oracle不太熟悉的人，可能就会采用 in或者exist关键字来进行筛选， 实际上Oracle有已经有递归查询的语法存在，对于Oracle不太熟悉的看官，可以百度一下。

这里列出了示例：

select t.project_id,t.project_name,t.p_project_id,t.p_project_name,t.category from sys_project_info s start with s.category in (10,11,21) connect by prior s.project_id=s.p_project_id and s.project_name = s.p_project_name;

　　

　　到这里数据的提取部分就已经完成，剩下的就是树形数据的组建过程，也就是数据的呈现。归根结底还是递归，在这里只是对递归过程进行了封装，可以直接移植到WPF或者Silverlight项目中，代码如下：

1 using Microsoft.Practices.Prism.ViewModel;  2 using System;  3 using System.Collections;  4 using System.Collections.Generic;  5 using System.Collections.ObjectModel;  6 using System.Linq;  7 using System.Runtime.Serialization;  8 using System.Text;  9  10 namespace SysManager.Utility 11 { 12     public class TreeNode
      
        : NotificationObject where T : BaseEntity 13     { 14         private T _parentNode; 15         private T _currentNode; 16         private bool _isChecked; 17         private bool _canChecked; 18  19         /// 
       
 20         /// 父节点 21         /// 
 22         public dynamic Key { get; set; } 23  24         /// 
       
 25         /// 子节点 26         /// 
 27         public ObservableCollection
       
        
         > ChildrenNodes { get; set; } 28  29         /// 
         
 30         /// 是否允许被选中 31         /// 
 32         public bool CanChecked 33         { 34             get { return _canChecked; } 35             set 36             { 37                 if (_canChecked == value) 38                     return; 39                 _canChecked = value; 40                 RaisePropertyChanged("CanChecked"); 41             } 42         } 43  44         /// 
         
 45         /// 是否处于被选中状态 46         /// 
 47         public bool IsChecked 48         { 49             get { return _isChecked; } 50             set 51             { 52                 if (_isChecked == value) 53                     return; 54                 _isChecked = value; 55                 RaisePropertyChanged("IsChecked"); 56             } 57         } 58         /// 
         
 59         /// 当前选中节点 60         /// 
 61         public T CurrentNode 62         { 63             get { return _currentNode; } 64             set 65             { 66                 if (_currentNode == value) 67                     return; 68                 _currentNode = value; 69                 RaisePropertyChanged("CurrentNode"); 70             } 71         } 72         /// 
         
 73         /// 当前节点的父级节点 74         /// 
 75         public T ParentNode 76         { 77             get { return _parentNode; } 78             set 79             { 80                 if (_parentNode == value) 81                     return; 82                 _parentNode = value; 83                 RaisePropertyChanged("ParentNode"); 84             } 85         } 86  87         public TreeNode() 88         { 89             this.CanChecked = true; 90         } 91  92         static TreeNode
         
           staticNode; 93  94         /// 
          
 95         /// 将数据组织成一个拥有上下级管理的树形结构数据集合 96         /// 
 97         /// 
          
           主键的数据类型
           98         /// 
          执行过GroupBy语句的数据源 99         /// 
          结果数据100         /// 
          子节点标识字段名称101         /// 
          父节点标识字段名称102         /// 
          103         /// 
          
           已生成的树形结构实体
          104         public TreeNode
          
            GenerateTreeNodes
           
            (IEnumerable
            
             
              > nodeSource, TreeNode
              
                resultTreeNode, string keyName, string parentKeyName)105 {106 var orderedSource = nodeSource.OrderBy(groupList => groupList.Key);107 foreach (IGrouping
               
                 item in orderedSource)108 {109 var listChildrenNode = new ObservableCollection
                
                 
                  >();110 object propertyParentValue = null;111 112 foreach (var child in item)113 {114 //get children id 115 object propertyValue = GetCurrentItemPropertyValue(keyName, child);116 //get parent id 117 if (propertyParentValue == null)118 propertyParentValue = GetCurrentItemPropertyValue(parentKeyName, child);119 120 if (propertyValue != propertyParentValue)121 {122 T parentNodeInstance = null;123 if (propertyParentValue != null)124 {125 var nodeParent = nodeSource.Where(x => x.Key.ToString() == propertyParentValue.ToString()).FirstOrDefault();126 if (nodeParent != null)127 parentNodeInstance = nodeParent.FirstOrDefault();128 }129 var node = new TreeNode
                  
                   () { CurrentNode = child, Key = propertyValue, ChildrenNodes = new ObservableCollection
                   
                    
                     >(), ParentNode = parentNodeInstance };130 listChildrenNode.Add(node);131 }132 133 }134 135 TreeNode
                     
                       parentNode = null;136 foreach (var root in listChildrenNode)137 {138 staticNode = null;139 parentNode = FindParentNode(resultTreeNode, item.Key);140 if (parentNode != null)141 break;142 }143 if (parentNode != null)144 {145 parentNode.ChildrenNodes = listChildrenNode;146 }147 else148 listChildrenNode.ToList().ForEach(childNode => resultTreeNode.ChildrenNodes.Add(childNode));149 150 }151 return resultTreeNode;152 }153 154 /// 
                      
155 /// 将一个拥有上下级关系的Tree转换为列表156 /// 
157 public IEnumerable TreeNode2LinkedList { get; private set; }158 /// 
                      
159 /// 将treenode转换为列表160 /// 
161 /// 
                      162 /// 
                      163 public void TreeNodeToLinkedList(TreeNode
                      
                        originalSource)164 {165 if (originalSource != null && originalSource.ChildrenNodes != null)166 {167 if (originalSource.CurrentNode != null)168 {169 if (TreeNode2LinkedList == null)170 TreeNode2LinkedList = new List
                       
                        ();171 (TreeNode2LinkedList as List
                        
                         ).Add(originalSource.CurrentNode);172 }173 foreach (var item in originalSource.ChildrenNodes)174 {175 TreeNodeToLinkedList(item);176 }177 }178 }179 180 private static object GetCurrentItemPropertyValue(string keyName, T child)181 {182 var property = child.GetType().GetProperties().Where(prop => prop.Name == keyName).FirstOrDefault();183 object propertyValue = null;184 if (property != null)185 propertyValue = property.GetValue(child, null);186 return propertyValue;187 }188 189 /// 
                         
190 /// 寻找当前节点的父级节点191 /// 
192 /// 
                         当前节点193 /// 
                         节点的Key194 /// 
                         
                          父级节点
                         195 private TreeNode
                         
                           FindParentNode(TreeNode
                          
                            rootNode, dynamic key)196 {197 198 if (rootNode.ChildrenNodes == null)199 return rootNode;200 foreach (var children in rootNode.ChildrenNodes)201 {202 if (children.Key == key)203 {204 staticNode = children;205 break;206 }207 else208 if (staticNode == null)209 FindParentNode(children, key);210 }211 if (rootNode.Key != null && (int)rootNode.Key == key)212 return rootNode;213 214 return staticNode;215 216 }217 }218 }
                          
                         
                        
                       
                      
                     
                    
                   
                  
                 
                
               
              
             
            
           
          
         
        
       
      

　　

//调用方法var treeNode = new TreeNode
     
      ();                    treeNode.GenerateTreeNodes
      
       (result.OfType
       
        ().GroupBy(proj => proj.ParentProjectId), treeNode, "ProjectId", "ParentProjectId");