C# 将扁平状数据链接成树状结构的通用方法
在项目中经常会遇到从数据库查询数据绑定到TreeVIew上,这时我们需要将查询出来的数据转换成树形结构数据,每次写觉得工作会很重复,所以写了一个通用的转换类。
第一步,我们需要建一个基类,这个基类的意义主要是扩展数据库实体类做连接用,用于确定树形结构中节点与子项的关系,
其中Parent为当前节点的父节点,Children为当前节点的子节点,IsLinked是判断当前节点是否已连接,用于防止数据中有循环依赖导致创建树的时候形成死循环。
TreeModel基类
public class TreeBase<T> { private bool isLinked = false; /// <summary> /// 是否已创建连接 /// </summary> public bool IsLinked { get { return isLinked; } set { isLinked = value; } } /// <summary> /// 父节点 /// </summary> public T Parent { get; set; } /// <summary> /// 子节点 /// </summary> public ObservableCollection<T> Children { get; set; } }
第二步,我们需要创建一个连接方法,将输入的扁平状数据转换为树状结构,我希望在使用的时候可以自己指定实体的哪个属性为ID,哪个为父ID
,这里我们使用了Expression,这样就可以使用linq表达式去指定属性了,剩下的就是利用反射获取实体的值与递归连接了,这样一个简单的通用创建树的方法就有了。
public class TreeHelper { /// <summary> /// 创建树 /// </summary> /// <typeparam name="T">实体类型</typeparam> /// <param name="root">根节点</param> /// <param name="list">所有数据</param> /// <param name="idProperty">节点唯一标识属性表达式</param> /// <param name="parentIdProperty">父节点属性表达式</param> public static void CreateTree<T>(T root, IList<T> list, string idPropertyName, string parentIdPropertyName) where T : TreeBase<T> { root.Children = new ObservableCollection<T>(); list.Where(e => (string)GetPropertyValue(e, parentIdPropertyName) == (string)GetPropertyValue(root, idPropertyName) && !e.IsLinked).ToList().ForEach(e => { root.Children.Add(e); e.IsLinked = true; }); foreach (var leaf in root.Children) { leaf.Parent = root; CreateTree<T>(leaf, list, idPropertyName, parentIdPropertyName); } } /// <summary> /// 创建多个根节点的树 /// </summary> /// <typeparam name="T">实体类型</typeparam> /// <param name="root">根节点</param> /// <param name="list">所有数据</param> /// <param name="idProperty">节点唯一标识属性表达式</param> /// <param name="parentIdProperty">父节点属性表达式</param> public static ObservableCollection<T> CreateTree<T>(IList<T> list, Expression<Func<T, object>> idProperty, Expression<Func<T, object>> parentIdProperty) where T : TreeBase<T> { //查找父节点不存在的leaf,作伪根节点 var roots = new ObservableCollection<T>(); var idPropertyName = GetMemberName(idProperty); var parentIdPropertyName = GetMemberName(parentIdProperty); list.Where(e => list.Count(item => (string)GetPropertyValue(item, idPropertyName) == (string)GetPropertyValue(e, parentIdPropertyName)) == 0).ToList().ForEach(e => roots.Add(e)); foreach (var root in roots) { CreateTree<T>(root, list, idPropertyName, parentIdPropertyName); } return roots; } private static object GetPropertyValue<T>(T t, string propertyName) { return t.GetType().GetProperty(propertyName).GetValue(t, null); } private static string GetMemberName<T, TMember>(Expression<Func<T, TMember>> propertySelector) { var propertyExp = propertySelector.Body as MemberExpression; if (propertyExp == null) { throw new ArgumentException("不合理的表达式!"); } return propertyExp.Member.Name; } }
使用示例:
先声明一个绑定实体,继承自TreeBase
public class Item : TreeBase<Item>
{
public string Id{get;set;}
public string ParentID{get;set;}
public string DisplayText{get;set;}
}
创建测试数据
IList<Item> data = new List<Item>(); var group1= new Item(){ Id = Guid.NewGuid().ToString(), DisplayText="Root"}; var item1 = new Item { Id = Guid.NewGuid().ToString(), ParentId = group1.Id, DisplayText = "Leaf1" }; var item2 = new Item { Id = Guid.NewGuid().ToString(), ParentId = group1.Id, DisplayText = "Leaf2" }; var item3 = new Item { Id = Guid.NewGuid().ToString(), ParentId = group1.Id, DisplayText = "Leaf3" }; var item4 = new Item() { Id = Guid.NewGuid().ToString(), ParentId = item3.Id, DisplayText = "Leaf3:Leaf1" }; var item5 = new Item() { Id = Guid.NewGuid().ToString(), ParentId = item3.Id, DisplayText = "Leaf3:Leaf2" }; var item6 = new Item() { Id = Guid.NewGuid().ToString(), ParentId = item3.Id, DisplayText = "Leaf3:Leaf3" }; data.Add(group1); data.Add(item1); data.Add(item2); data.Add(item3); data.Add(item4); data.Add(item5); data.Add(item6);
界面模板绑定
<TreeView Height="245" HorizontalAlignment="Left" Margin="46,35,0,0" Name="treeView1" VerticalAlignment="Top" Width="156" > <TreeView.ItemTemplate> <HierarchicalDataTemplate ItemsSource="{Binding Children}"> <TextBlock Text="{Binding DisplayText}"></TextBlock> </HierarchicalDataTemplate> </TreeView.ItemTemplate> </TreeView>
后台数据绑定
treeView1.ItemsSource = TreeHelper.CreateTree<Item>(data, item => item.Id, item => item.ParentId);
以后绑定树形数据是不是很简单呢?
这种方法不适应主键为Guid的数据类型
因为以下代码无法获取Guid类型的名称,欢迎各位大叔,大婶,大神们指点
private static string GetMemberName<T, TMember>(Expression<Func<T, TMember>> propertySelector) { var propertyExp = propertySelector.Body as MemberExpression; if (propertyExp == null) { throw new ArgumentException("不合理的表达式!"); } return propertyExp.Member.Name; }
本文来自博客园,作者:广林,转载请注明原文链接:https://www.cnblogs.com/guanglin/archive/2013/03/13/2948410.html