如何动态填充树视图(C#)

Question

我有一个包含3列的表,ID,Name和ParentID.ID列包含运行编号,该编号也用作主键.ID也将是节点的Name属性.Name列包含将成为treenode的Text属性的字符串,而ParentID是包含节点的父ID的列.

这是我的表格的样子:

ID     Name   ParentID
======================
1      A      0
2      A1     1
3      B      0
4      C      0
5      A2     1
6      B1     3

此表显示节点A是节点A1和A2的父节点.ParentID等于"0"表示节点的父节点是根节点(硬编码).例如,节点A,B和C是根节点的子节点.

在填充树视图之前,我按ParentID对行进行排序.我使用这两种方法填充树视图(这里的TreeNode节点是填充到树中的子节点):

    private void SearchParent(TreeView tree, String parentID, TreeNode node)
    {
        // Post: call TraverseParent method to search parent

        TreeNodeCollection collection = tree.Nodes;

        // Search parent recursively
        foreach (TreeNode n in collection)
        {
            TraverseParent(n, parentID, node);
        }
    }

    private void TraverseParent(TreeNode potentialParent, String parentID, TreeNode node)
    {
        // Post: search for parent. When parent is found add child to parent

        // am i the parent that you're looking for?
        if (parentID.CompareTo(potentialParent.Name) == 0)
        {
            // found me! i'm your parent!

            // add child to parent
            potentialParent.Nodes.Add(node);

            // update that the parent for child has been found
            parentFound = true;
        }
        else
        {
            // i'm not your parent

            // continue to look for parent recursively
            foreach (TreeNode n in potentialParent.Nodes)
            {
                TraverseParent(n, parentID, node);
            }
        }
    }

一切顺利,直到我通过使节点A成为节点C的子节点并将更改提交到数据库来拖放节点.

现在我的数据库表看起来像这样:

ID     Name   ParentID
======================
1      A      4
2      A1     1
3      B      0
4      C      0
5      A2     1
6      B1     3

下次运行应用程序时,它无法将节点A1和A2填充到树中,因为它找不到它们的父节点.这是因为当我在填充树视图之前根据ParentID对行进行排序时,行的排序方式如下:

ID     Name   ParentID
======================
3      B      0
4      C      0
2      A1     1
5      A2     1
6      B1     3
1      A      4

这样,我的应用程序将尝试在创建节点A之前将A1和A2节点填充到树中.因此,应用程序找不到节点A1和A2的父节点.

因此,任何人都可以告诉我修复此错误的方法,还是有更好的方法来动态填充树视图？

谢谢.

Answer 1

您应该使用递归来填充它.

承诺的例子:

public partial class Form1 : Form
    {
        private class ItemInfo
        {
            public int ID;
            public int ParentID;
            public string Name;
        }

        public Form1()
        {
            InitializeComponent();
            FillTreeView();
        }

        private void FillTreeView()
        {
            var items = new List<ItemInfo>()
            {
                new ItemInfo(){ID = 1, ParentID = 4, Name = "A"},
                new ItemInfo(){ID = 2, ParentID = 1, Name = "A1"},
                new ItemInfo(){ID = 3, ParentID = 0, Name = "B"},
                new ItemInfo(){ID = 4, ParentID = 0, Name = "C"},
                new ItemInfo(){ID = 5, ParentID = 1, Name = "A2"},
                new ItemInfo(){ID = 6, ParentID = 3, Name = "B1"},
            };

            FillNode(items, null);
        }

        private void FillNode(List<ItemInfo> items, TreeNode node)
        {
            var parentID = node != null
                ? (int)node.Tag
                : 0;

            var nodesCollection = node != null
                ? node.Nodes
                : treeView1.Nodes;

            foreach (var item in items.Where(i => i.ParentID == parentID))
            {
                var newNode = nodesCollection.Add(item.Name, item.Name);
                newNode.Tag = item.ID;

                FillNode(items, newNode);
            }
        }
    }