c# - 创建自定义TreeView/TreeNode

我需要扩展treenode类，以便可以向每个节点添加自定义属性（正如webforms treenode不包括tag属性一样）。所以这是我的客户地址：

public class CustomTreeNode : TreeNode
{

    public CustomTreeNode()
    {
    }

    public CustomTreeNode(int nodeId, string nodeType)
    {
        NodeId = nodeId;
        NodeType = nodeType;
    }

    public string NodeType { get; set; }
    public int NodeId { get; set; }
}

如果我创建一个customtreenode并将其添加到treeview：

CustomTreeNode node = new CustomTreeNode(1, "CustomType");
treeView.Nodes.Add(node);

然后我会得到一个铸造异常，执行以下操作：

CustomTreeNode selectedNode = (CustomTreeNode)TreeView.SelectedNode;

因为treeview返回的是treenode，而不是customtreenode。
我已经做了一些阅读，看起来我需要扩展treeview类，并重写createnode（）方法以返回customtreenode而不是treenode。所以我创造了这个：

public class CustomTreeView : TreeView
{
    protected override TreeNode CreateNode()
    {
        return new CustomTreeNode();
    }
}

但是，问题是createnode（）不接受任何参数，因此必须为customtreenode类调用空构造函数。因此，当我在上面创建customtreenode时，当我从customtreeview获取它时，nodeid和nodetype值已经丢失，因为空构造函数返回一个没有任何值的节点。
非常感谢您的帮助。

最佳答案

这就是我想到的（专家，欢迎任何建议）。在代码后面实例化CustomTreeNodes并通过setter设置属性。修改CustomTreeNode类以将值持久化在viewstate中。自定义树视图的CreateNode返回的节点将加载viewstate信息。
Treenode类：

[DefaultProperty("Text")]
[ToolboxData("<{0}:CustomTreeNode runat=server></{0}:CustomTreeNode>")]
public class CustomTreeNode : TreeNode
{
    private const int NODE_TYPE = 1;
    private const int NODE_ID = 2;

    public string NodeType { get; set; }
    public int NodeId { get; set; }

    protected override void LoadViewState(Object savedState)
    {
        if (savedState != null)
        {
            object[] myState = (object[])savedState;
            if (myState[0] != null)
                base.LoadViewState(myState[0]);
            if (myState[NODE_TYPE] != null)
                this.NodeType = (string)myState[NODE_TYPE];
            if (myState[NODE_ID] != null)
                this.NodeId = (int)myState[NODE_ID];

        }
    }

    protected override Object SaveViewState()
    {
        object baseState = base.SaveViewState();
        object[] allStates = new object[3];
        allStates[0] = baseState;
        allStates[NODE_TYPE] = this.NodeType;
        allStates[NODE_ID] = this.NodeId;

        return allStates;
    }
}

TreeView类：

[DefaultProperty("Text")]
[ToolboxData("<{0}:CustomTreeView runat=server></{0}:CustomTreeView>")]
public class CustomTreeView : TreeView
{
    protected override TreeNode CreateNode()
    {
        // Tree node will get its members populated with the data from VIEWSTATE
        return new CustomTreeNode();
    }
}

简单的.aspx文件（假设您的自定义控件是在程序集“foo”和命名空间“bar”中定义的）：

<%@ Register TagPrefix="customControl" Assembly="Foo" Namespace="Bar"  %>

<customControl:CustomTreeView ID="sampleTree"
    runat="server" onselectednodechanged="sampleTree_SelectedNodeChanged"></customControl:CustomTreeView>
<asp:Label ID="lblSelectedNode" runat="server" ></asp:Label>

代码隐藏：

    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            PopulateTree();
        }
    }

    private void PopulateTree()
    {
        sampleTree.Nodes.Clear();
        CustomTreeNode root = new CustomTreeNode();
        root.Value = "root node";

        sampleTree.Nodes.Add(root);

        // Creating some fake nodes (you would of course be using real data)
        for (int i = 0; i < 10; i++)
        {
            CustomTreeNode child = new CustomTreeNode();
            child.NodeId = i;               // Saved in ViewState
            child.NodeType = "Type " + i;   // Saved in ViewState
            child.Value = child.NodeType;
            root.ChildNodes.Add(child);
        }
    }

    protected void sampleTree_SelectedNodeChanged(object sender, EventArgs e)
    {
        CustomTreeView cTreeView = (CustomTreeView) sender;
        lblSelectedNode.Text = ((CustomTreeNode)cTreeView.SelectedNode).NodeType;
    }