Windows Forms VB.NET-用分层数据填充TreeView [英] Windows Forms VB.NET - Populate TreeView with Hierarchical data
问题描述
喂，我正在尝试使用来自SQL数据库的分层数据填充Windows窗体应用程序上的树状视图.
Aloha, I'm trying to populate a treeview on a windows form app with Hierarchical data from a SQL db.
数据库的结构为:
id_def id_parent description
1 NULL Multidificiência
2 NULL Síndrome
3 NULL Outros
4 1 Surdez de Transmissão
5 2 Surdez Neurossensorial Ligeira
6 3 Surdez Neurossensorial Média
在id_parent中具有NULL值的记录是主要类别，而在其id_parent中具有NULL值的记录是子类别.
the records with NULL value at id_parent, are the main categories, and the ones with their id_parent, are sub categories.
任何人都可以使用代码来填充TreeView吗?我设法用ASP.NET应用程序做到了，如果有帮助，则代码如下:
Can anyone help with the code to populate the TreeView ? I managed to do it with an ASP.NET app, if it helps, here's the code:
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
PopulateRootLevel();
}
private void PopulateRootLevel()
{
SqlConnection objConn = new SqlConnection("Data Source=1.1.1.1;Initial Catalog=DREER_EDUCANDOS2006;User ID=sre_web;Password=xxx");
SqlCommand objCommand = new SqlCommand("select id_deficiencia,descricao,(select count(*) FROM NecessidadesEspeciais WHERE id_deficiencia_pai=sc.id_deficiencia) childnodecount FROM NecessidadesEspeciais sc where id_deficiencia_pai IS NULL", objConn);
SqlDataAdapter da = new SqlDataAdapter(objCommand);
DataTable dt = new DataTable();
da.Fill(dt);
PopulateNodes(dt, TreeView1.Nodes);
}
private void PopulateSubLevel(int parentid, TreeNode parentNode)
{
SqlConnection objConn = new SqlConnection("Data Source=1.1.1.1;Initial Catalog=DREER_EDUCANDOS2006;User ID=sre_web;Password=xxx");
SqlCommand objCommand = new SqlCommand("select id_deficiencia,descricao,(select count(*) FROM NecessidadesEspeciais WHERE id_deficiencia_pai=sc.id_deficiencia) childnodecount FROM NecessidadesEspeciais sc where id_deficiencia_pai=@id_deficiencia_pai", objConn);
objCommand.Parameters.Add("@id_deficiencia_pai", SqlDbType.Int).Value = parentid;
SqlDataAdapter da = new SqlDataAdapter(objCommand);
DataTable dt = new DataTable();
da.Fill(dt);
PopulateNodes(dt, parentNode.ChildNodes);
}
protected void TreeView1_TreeNodePopulate(object sender, TreeNodeEventArgs e)
{
PopulateSubLevel(Int32.Parse(e.Node.Value), e.Node);
}
private void PopulateNodes(DataTable dt, TreeNodeCollection nodes)
{
foreach (DataRow dr in dt.Rows)
{
TreeNode tn = new TreeNode();
tn.Text = dr["descricao"].ToString();
tn.Value = dr["id_deficiencia"].ToString();
nodes.Add(tn);
//If node has child nodes, then enable on-demand populating
tn.PopulateOnDemand = ((int)(dr["childnodecount"]) > 0);
}
}
推荐答案
获取一个包含一些分层数据的表:
Take a table with some hierarchical data in it:
Id Name ParentNodeId
1 Top-level node 1 -1
2 A first-level child 1
3 Another top-level node -1
4 Another first-level child 1
5 First-level child in another branch 3
6 A second-level child 2
我已经重新整理了另一个SO答案中的示例代码，使用上面的表动态填充树状视图(假设该表位于SQL Server数据库中).代码示例有些冗长...
I have reworked the sample code from another SO answer, to use the above table to dynamically populate a tree view (assuming the table lives in an SQL server database). The code sample is somewhat lenghty...
using System.Windows.Forms;
using System.Threading;
using System.Collections.Generic;
using System.Data.SqlClient;
public class TreeViewSample : Form
{
private TreeView _treeView;
public TreeViewSample()
{
this._treeView = new System.Windows.Forms.TreeView();
this._treeView.Location = new System.Drawing.Point(12, 12);
this._treeView.Size = new System.Drawing.Size(200, 400);
this._treeView.AfterExpand +=
new TreeViewEventHandler(TreeView_AfterExpand);
this.ClientSize = new System.Drawing.Size(224, 424);
this.Controls.Add(this._treeView);
this.Text = "TreeView Lazy Load Sample";
PopulateChildren(null);
}
void TreeView_AfterExpand(object sender, TreeViewEventArgs e)
{
if (e.Node.Nodes.Count == 1 && e.Node.Nodes[0].Tag == "dummy")
{
PopulateChildren(e.Node);
}
}
private void PopulateChildren(TreeNode parent)
{
// this node has not yet been populated, launch a thread
// to get the data
int? parentId = parent != null ? (parent.Tag as DataNode).Id : (int?)null;
ThreadPool.QueueUserWorkItem(state =>
{
IEnumerable<DataNode> childItems = GetNodes(parentId);
// load the data into the tree view (on the UI thread)
_treeView.BeginInvoke((MethodInvoker)delegate
{
PopulateChildren(parent, childItems);
});
});
}
private void PopulateChildren(TreeNode parent, IEnumerable<DataNode> childItems)
{
TreeNodeCollection nodes = parent != null ? parent.Nodes : _treeView.Nodes;
TreeNode child;
TreeNode dummy;
TreeNode originalDummyItem = parent != null ? parent.Nodes[0] : null;
foreach (var item in childItems)
{
child = new TreeNode(item.Text);
child.Tag = item;
dummy = new TreeNode("Loading. Please wait...");
dummy.Tag = "dummy";
child.Nodes.Add(dummy);
nodes.Add(child);
}
if (originalDummyItem != null)
{
originalDummyItem.Remove();
}
}
private IEnumerable<DataNode> GetNodes(int? parentId)
{
List<DataNode> result = new List<DataNode>();
using (SqlConnection conn = new SqlConnection(@"[your connection string]"))
using (SqlCommand cmd = new SqlCommand("select * from Nodes where ParentNodeId = @parentNodeId", conn))
{
cmd.Parameters.Add(new SqlParameter("@parentNodeId", System.Data.SqlDbType.Int));
cmd.Parameters["@parentNodeId"].Value = parentId != null ? parentId : -1;
conn.Open();
using (SqlDataReader reader = cmd.ExecuteReader())
{
int nodeIdCol = reader.GetOrdinal("NodeId");
int nameCol = reader.GetOrdinal("Name");
int parentIdCl = reader.GetOrdinal("ParentNodeId");
while (reader.Read())
{
result.Add(new DataNode
{
Id = reader.GetInt32(nodeIdCol),
Text = reader.GetString(nameCol),
ParentId = reader.IsDBNull(parentIdCl) ? (int?)null : reader.GetInt32(parentIdCl)
});
}
}
}
return result;
}
}
public class DataNode
{
public int Id { get; set; }
public string Text { get; set; }
public int? ParentId { get; set; }
}
使用Linq-to-SQL可以使数据获取代码更漂亮，但是我希望数据获取代码尽可能完整，因此我决定省略该代码，以减少代码量.(这将需要包含一些生成的Linq-to-SQL类).
The data fetching code can probably be made a bit prettier by using Linq-to-SQL, but I wanted the same to be as complete as possible, so I decided to leave that out to keep the amount of code down... (that would require the inclusion of some generated Linq-to-SQL classes).
这篇关于Windows Forms VB.NET-用分层数据填充TreeView的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
