WPF树形菜单--递归与非递归遍历生成树结构的集合

一、新建了WPF项目作为测试，使用TreeView控件进行界面展示。

第一步创建实体类TreeEntity：

public class TreeEntity
{
    private int _mid;
    private string _title;
    private int _pid;
    private List<TreeEntity> _childrens=new List<TreeEntity>();
    /// <summary>
    /// 项ID
    /// </summary>
    public int Mid
    {
        get { return _mid; }
        set
        {
            _mid = value;
        }
    }
    /// <summary>
    /// 项名称
    /// </summary>
    public string Title
    {
        get { return _title; }
        set
        {
            _title = value;
        }
    }
    /// <summary>
    /// 父亲ID
    /// </summary>
    public int Pid
    {
        get { return _pid; }
        set
        {
            _pid = value;
        }
    }

    /// <summary>
    /// 儿子们
    /// </summary>
    public List<TreeEntity> Childrens
    {
        get { return _childrens; }
        set
        {
            _childrens = value;
        }
    }
}

第二部构造无层级的数据源：

TreeEntity yeye = new TreeEntity()
{
    Mid = ,
    Title = "猪爷爷",
    Pid =
};
TreeEntity laolao = new TreeEntity()
{
    Mid = ,
    Title = "猪姥姥",
    Pid =
};
TreeEntity baba = new TreeEntity()
{
    Mid = ,
    Title = "猪爸爸",
    Pid =
};
TreeEntity mama = new TreeEntity()
{
    Mid = ,
    Title = "猪妈妈",
    Pid =
};
TreeEntity peiqi = new TreeEntity()
{
    Mid = ,
    Title = "佩奇",
    Pid =
};
TreeEntity peizierzi = new TreeEntity()
{
    Mid = ,
    Title = "小佩佩奇",
    Pid =
};
TreeEntity peiqisunzi = new TreeEntity()
{
    Mid = ,
    Title = "佩奇的孙子",
    Pid =
};
TreeEntity peiqinver = new TreeEntity()
{
    Mid = ,
    Title = "小佩佩妞",
    Pid =
};
TreeEntity qiaozhi = new TreeEntity()
{
    Mid = ,
    Title = "乔治",
    Pid =
};
List<TreeEntity> treeEntities = new List<TreeEntity>()
{
    yeye,
    laolao,
    mama,
    peiqi,
    peiqinver,
    peiqisunzi,
    qiaozhi,
    peizierzi
};

第三步实现树形集合的构造

方法一：使用递归方法构造

1)、先取出顶级数据项--即无父亲的项

List<TreeEntity> rootLists = treeEntities.Where(x => x.Pid == ).ToList();
for (int i = ; i < rootLists.Count; i++)
{
    rootLists[i].Childrens = CreateTree(rootLists[i].Mid, treeEntities);
}

2）、再遍历上一步取得的数据项，使用递归获取所有子项

private List<TreeEntity> CreateTree(int pid, List<TreeEntity> sources)
{
    List<TreeEntity> childrens = new List<TreeEntity>();
    if (sources != null && sources.Count > )
    {
        childrens = sources.Where(x => x.Pid == pid).ToList();
        if (childrens != null & childrens.Count > )
        {
            foreach (var item in childrens)
            {
                item.Childrens = CreateTree(item.Mid, sources);
            }
        }
    }
    return childrens;
}

3）、将集合绑定给TreeView的数据源

MyTreeList.ItemsSource = rootLists;

方法二：非递归遍历

1)、将所有数据项装进字典中 字典中的键为 当前实例的ID；字典中的项为当前实例

Dictionary<int, TreeEntity> valuePairs = new Dictionary<int, TreeEntity>();
foreach (var item in treeEntities)
{
    valuePairs[item.Mid] = item;
}
List<TreeEntity> rootLists =CreateTreeQuick(valuePairs);

2）、遍历字典中的所有Values，向当前项(item)的PID对应的实例中添加当前项(item)

private List<TreeEntity> CreateTreeQuick(Dictionary<int, TreeEntity> keyValues)
{
    List<TreeEntity> myTree = new List<TreeEntity>();
    foreach (var item in keyValues.Values)
    {
        if (item.Pid==)
        {
            myTree.Add(item);
        }
        else
        {
            if (keyValues.ContainsKey(item.Pid))
            {
                keyValues[item.Pid].Childrens.Add(item);
            }
        }
    }
    return myTree;
}

3)、将集合绑定到TreeView控件的数据源中

MyTreeList.ItemsSource = rootLists;

二、WPF前台布局

<TreeView x:Name="MyTreeList" Width="200">
    <TreeView.ItemTemplate>
        <HierarchicalDataTemplate DataType="{x:Type local:TreeEntity}" ItemsSource="{Binding Childrens}">
            <TextBlock Text="{Binding Title}"/>
        </HierarchicalDataTemplate>
    </TreeView.ItemTemplate>
</TreeView>