创建自定义TreeView / TreeNode

我需要扩展TreeNode类，以便我可以为每个节点添加自定义属性（看作WebForms TreeNode不包含Tag属性）。 所以这是我的CustomTreeNode：

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); 

然后我会得到一个执行以下的转换exception：

 CustomTreeNode selectedNode = (CustomTreeNode)TreeView.SelectedNode; 

因为TreeView返回TreeNode，而不是CustomTreeNode。

我做了一些阅读，看起来我需要扩展TreeView类，并覆盖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(); } } 

但问题是，CreateNode（）不接受任何参数，因此您必须调用CustomTreeNode类的空构造函数。 因此，当我在上面创建CustomTreeNode时，当我从CustomTreeView返回时，nodeId和nodeType值已经丢失，因为空构造函数返回没有任何值的节点。

任何帮助非常感谢。

Answer 1

这就是我提出的（专家，欢迎任何建议）。 在后面的代码中实例化CustomTreeNode并通过setter设置属性。 修改CustomTreeNode类以在ViewState中保留值。 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>")] 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>")] 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在程序集“Foo”和名称空间“Bar”中定义：

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

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; }