visual studio 2012中的简单树视图控件 [英] simple treeview control in visual studio 2012

问题描述

你好，我正在尝试在visual studio 2012 asp.net4.5，c＃和MySql Database中使用treeview。我从工具箱中取出了treeview控件并填充它。

但它没有显示任何输出。它显示空白屏幕

我的数据库包含两个表格，即主题（subject_id，subject_name）&主题（topic_id，subject_id，主题）

它显示空白输出。没有错误.plz帮助我。

hello, I am using trying to use treeview in visual studio 2012 asp.net4.5,c#, and MySql Database. I took treeview control from toolbox and populated it.
But it does not show any output. it shows blank screen
my database contains two tables table i.e subject(subject_id,subject_name) & topic(topic_id,subject_id,topics)
It shows blank output.there is no error.plz help me with this.

public partial class Study : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
PopulateRootLevel();
}
private void PopulateRootLevel()
{
try
{
MySqlConnection con = new MySqlConnection(@"User Id=root;Host=localhost;Database=helix");
MySqlCommand cmd = new MySqlCommand(@"SELECT topic_id,topics,(SELECT count(*) FROM topic WHERE subject_id=sc.topic_id) childnodecount FROM topic sc WHERE subject_id IS NULL ", con);
con.Open();
MySqlDataAdapter da = new MySqlDataAdapter(cmd);
DataTable dt = new DataTable();
da.Fill(dt);
PopulateNodes(dt, TreeView1.Nodes);
con.Close();
}
catch (Exception ex)
{
throw ex;
}
}
private void PopulateSublevel(int subject_id, TreeNode parentNode)
{
try
{
MySqlConnection con = new MySqlConnection(@"User Id=root;Host=localhost;Database=helix");
MySqlCommand cmd = new MySqlCommand(@"SELECT topic_id,topics,(SELECT count(*) FROM topic WHERE subject_id=sc.topic_id) childnodecount FROM topic sc WHERE subject_id=@subject_id ", con);
con.Open();
cmd.Parameters.Add("@subject_id", MySqlDbType.Int32).Value = subject_id;
MySqlDataAdapter da = new MySqlDataAdapter(cmd);
DataTable dt = new DataTable();
da.Fill(dt);
PopulateNodes(dt, parentNode.ChildNodes);
con.Close();
}
catch(Exception ex)
{
throw ex;
}
}
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["topics"].ToString();
tn.Value = dr["topic_id"].ToString();
nodes.Add(tn);
tn.PopulateOnDemand = ((int)(dr["childnodecount"]) > 0);
}
}
}

<asp:TreeView

ID="TreeView1"

ExpandDepth="0"

PopulateNodesFromClient="true"

ShowLines="true"

ShowExpandCollapse="true"

runat="server"

OnTreeNodePopulate="TreeView1_TreeNodePopulate" />

推荐答案

这可能对你有帮助..



http://stackoverflow.com/questions/361661/populate-treeview-from-database [ ^ ]

this might help you..

http://stackoverflow.com/questions/361661/populate-treeview-from-database[^]

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