TreeView 采購單樹狀展示：數據綁定與遞歸構建

數據模型

class PurchaseNode {
    int id;
    int parentId;  // 0 為根
    String name;
    List<PurchaseNode> children;
}

遞歸構建樹 (C# WinForm)

void BuildTree(TreeNode parentNode, List<PurchaseNode> allNodes) {
    var children = allNodes.Where(n => n.parentId == (int)parentNode.Tag).ToList();
    foreach (var child in children) {
        TreeNode node = new TreeNode(child.name) { Tag = child.id };
        parentNode.Nodes.Add(node);
        BuildTree(node, allNodes);  // 遞歸
    }
}

// 調用
var root = new TreeNode("采購單") { Tag = 0 };
BuildTree(root, allNodes);
treeView1.Nodes.Add(root);
treeView1.ExpandAll();

VB.NET 版本

Sub BuildTree(parentNode As TreeNode, allNodes As List(Of PurchaseNode))
    Dim children = allNodes.Where(Function(n) n.parentId = CInt(parentNode.Tag)).ToList()
    For Each child In children
        Dim node As New TreeNode(child.name) With {.Tag = child.id}
        parentNode.Nodes.Add(node)
        BuildTree(node, allNodes)
    Next
End Sub

數據庫查詢優化

-- 單次查詢所有節點
SELECT id, parent_id, name FROM purchase_order WHERE order_id = @id ORDER BY parent_id, id;

-- C# 端構建查找表
var lookup = allNodes.ToLookup(n => n.parentId);  // O(1) 查找子節點
// BuildTree 內部用 lookup[parentId] 替代 Where

大數據懶加載

• TreeNode Tag 存節點 ID，Nodes.Add(new TreeNode("Loading...")) 佔位。
• BeforeExpand 事件中動態查詢子節點並替換佔位節點。

常見問題