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TreeViewThe control is used to display hierarchical data. It displays information in a tree structure. Each node can have one or more child nodes. TreeView Control allows users to view complex hierarchical information in expandable and collapsible forms.
TreeViewbasic knowledge
Attributes
- Nodes: A TreeNodeCollection that contains the root node of the control.
- SelectedNode: Get or set the currently selected TreeNode.
- CheckBoxes: Determines whether to display a checkbox next to each tree node.
- ShowPlusMinus: Determines whether to display plus and minus signs for expanding and collapsing tree nodes.
- ShowLines: Determines whether to display connecting lines between tree nodes.
method
- BeginUpdate(): Pauses the drawing control, which can be used to avoid redrawing and improve performance when adding a large number of nodes.
- EndUpdate(): Resumes the normal drawing control, used in conjunction with
BeginUpdate(). - CollapseAll(): Collapse all tree nodes.
- ExpandAll(): Expand all tree nodes.
- GetNodeAt(): Returns the TreeNode located at the specified point.
event
- AfterCheck / BeforeCheck: After the node’s checkbox is selected or unchecked by the user/ happened before.
- AfterSelect / BeforeSelect: Occurs after/before selecting a node.
- AfterCollapse / BeforeCollapse: Occurs after/before the node is collapsed.
- AfterExpand / BeforeExpand: Occurs after/before the node is expanded.
- NodeMouseClick: Occurs when the mouse clicks on a TreeNode.
Node introduction - TreeNode
- Name: The unique identifier of the node.
- Text: The text displayed by the node.
- Nodes: A collection of child nodes.
Dynamically load menu table
- The relationship between nodes and sub-nodes is stored in the database, but the hierarchical relationship is not obvious.
- The process of dynamically loading data into the TreeView control:
- Get table data from database.
- Nodes are created using a recursive method and added to the TreeView.
- Call methods to create and display hierarchical data in a TreeView.
Check processing of TreeView nodes
- When the parent node is checked or unchecked, the status of all child nodes changes accordingly.
- If any child node is checked, the parent node should also be checked.
- All child nodes are unchecked, and neither are the parent nodes.
TreeViewCase presentation
Case number one:
namespace WinFormsTest
{
public partial class frmTreeView : Form
{
public frmTreeView()
{
InitializeComponent();
}
private void frmTreeView_Load(object sender, EventArgs e)
{
TreeView fileTree = new TreeView();
// 单独设置 Width 和 Height
fileTree.Width = 200; // 设置宽度为200像素
fileTree.Height = 600; // 设置高度为400像素
// 或者使用 Size 属性同时设置宽度和高度
fileTree.Size = new Size(200, 300); // 宽度200像素，高度400像素
// 开始更新节点，防止在添加节点时进行重绘
fileTree.BeginUpdate();
TreeNode rootNode = new TreeNode("我的电脑");
fileTree.Nodes.Add(rootNode);
// 添加几个文件夹作为子节点
TreeNode documentsNode = new TreeNode("文档");
TreeNode picturesNode = new TreeNode("图片");
TreeNode musicNode = new TreeNode("音乐");
TreeNode videoNode = new TreeNode("视频");
rootNode.Nodes.Add(documentsNode);
rootNode.Nodes.Add(picturesNode);
rootNode.Nodes.Add(musicNode);
rootNode.Nodes.Add(videoNode);
// 完成节点添加后，恢复控件的绘制
fileTree.EndUpdate();
fileTree.AfterSelect += new TreeViewEventHandler(fileTree_AfterSelect);
this.Controls.Add(fileTree);
}
private void fileTree_AfterSelect(object sender, TreeViewEventArgs e)
{
if (e.Node.Text != "我的电脑")
{
// 当用户选择一个节点时，显示选中节点的信息
MessageBox.Show("选中的文件夹: " + e.Node.Text);
}
}
}
}
Effect:
Case 2:
using System.Data;
using WinFormsTest.Helper;
namespace WinFormsTest
{
public partial class frmTreeView2 : Form
{
public frmTreeView2()
{
InitializeComponent();
}
private void frmTreeView2_Load(object sender, EventArgs e)
{
treeView1.Nodes.Clear();//清除所有节点
//1. 获取数据
DataTable dtMenus = DBHelper.GetDataTable("select Id,MName,ParentId from MenuInfos", 1);
//3.调用方法,添加节点
CreateNode(dtMenus, null, 0);
}
//2.添加节点（递归）
private void CreateNode(DataTable dt, TreeNode pNode, int parentId)
{
//1.获取要创建的节点数据
DataRow[] rows = dt.Select("ParentId=" + parentId);
if (rows.Length > 0)
{
foreach (DataRow r in rows)
{
//2.新建子节点
TreeNode node = new TreeNode();
node.Name = r["Id"].ToString();
node.Text = r["MName"].ToString();
//3.直接添加到TreeView Nodes 还是添加指定节点的Nodes里？
if (pNode != null)
pNode.Nodes.Add(node);
else
treeView1.Nodes.Add(node);
//4.判断当前节点下有没有子节点
//这个是递归，直到rows为0即当前节点没有子节点时结束递归
CreateNode(dt, node, int.Parse(node.Name));
}
}
}
/添加父子勾选关联功能
//1.父节点勾选或取消，它的所有子节点与它一致
//2.只要有一个子节点勾选，父节点就勾选
// 子节点全部不勾选，父节点就不勾选
bool isMouseClick = true;
private void treeView1_NodeMouseClick_1(object sender, TreeNodeMouseClickEventArgs e)
{
isMouseClick = false;
//子节点勾选
SetChildNodesState(e.Node);
//父节点勾选
SetParentNodeState(e.Node);
isMouseClick = true;
}
private void treeView1_AfterCheck_1(object sender, TreeViewEventArgs e)
{
if (isMouseClick)
{
treeView1.SelectedNode = e.Node; //当前操作节点选中
}
}
//递归处理子节点的勾选
private void SetChildNodesState(TreeNode node)
{
if (node.Nodes.Count > 0)
{
foreach (TreeNode n in node.Nodes)
{
n.Checked = node.Checked;
SetChildNodesState(n);
}
}
}
private void SetParentNodeState(TreeNode node)
{
TreeNode pNode = node.Parent;//获取父节点
if (pNode != null)
{
bool bl = false;
foreach (TreeNode n in pNode.Nodes)
{
if (n.Checked)
{
bl = true;
break;
}
}
pNode.Checked = bl;
SetParentNodeState(pNode);
}
}
}
}
Effect:
Create a new SQL database
exhibit
After adding the parent-child check association function
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