Treeview Loaded Empty

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Hello,

I am trying to load treeview dynamically but when i run the project windows shows empty.Please review my code and tell me where i have mistaken.

public partial class Form1 : Form
{
	TreeNode parentNode = null;
	public Form1()
	{
		InitializeComponent();
	}

	private void Form1_Load(object sender, EventArgs e)
	{
		//TreeNode node = new TreeNode("Windows");
		using (SqlConnection con = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["ConnString"].ConnectionString))
		{
			using (SqlDataAdapter adapt = new SqlDataAdapter("Select * from TreeviewTable", con))
			{
				DataTable dt = new DataTable();
				adapt.Fill(dt);
				foreach (DataRow row in dt.Rows)
				{
					parentNode = treeView1.Nodes.Add(row["NodeName"].ToString());
					PopulateTreeview(Convert.ToInt32(row["TreeviewId"].ToString()), parentNode);
				}

				treeView1.ExpandAll();
			}
		}
	}

	private void PopulateTreeview(int _parentId, TreeNode _parentnode)
	{
		using (SqlConnection con = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["ConnString"].ConnectionString))
		{
			using (SqlDataAdapter adapt = new SqlDataAdapter("Select * from dbo.SubMenuTable Where ParentId=" + _parentnode, con))
			{
				DataTable dt = new DataTable();
				adapt.Fill(dt);
				TreeNode childnode;
				foreach (DataRow row in dt.Rows)
				{
					if (_parentnode == null)
						childnode = treeView1.Nodes.Add(row["SubMenuName"].ToString());
					else
						childnode = _parentnode.Nodes.Add(row["SubMenuName"].ToString());
					PopulateTreeview(Convert.ToInt32(row["SubMenuId"].ToString()), childnode);
				}
			}
		}
	}
}

Posted 18-Nov-14 20:14pm

ajays3356

Updated 18-Nov-14 23:42pm

BillWoodruff

v2

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Comments

BillWoodruff 19-Nov-14 5:48am

0. no errors: correct ?

1. Is it possible that the DataSet is empty ? Put a break-point here and examine the contents of 'dt

adapt.Fill(dt);
foreach (DataRow row in dt.Rows)

2. are any nodes actually being created: put a break-point on

parentNode = treeView1.Nodes.Add(row["NodeName"].ToString());
PopulateTreeview(Convert.ToInt32(row["TreeviewId"].ToString()), parentNode);

and examine the contents of each node created: does the NodeName show up as expected ?

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Richard Deeming · Answer 1 · 2014-11-19T04:44:00

ajays3356534 wrote:

C#

using (SqlDataAdapter adapt = new SqlDataAdapter("Select * from dbo.SubMenuTable Where ParentId=" + _parentnode, con))

First problem: You're trying to pass _parentnode to the query. I suspect you meant to pass _parentId instead.

Second problem: NEVER use string concatenation to build a SQL query. ALWAYS use a parameterized query.

Although in this particular case, since you're passing an int, your code won't be vulnerable to SQL Injection[^], you should still avoid using string concatenation. Otherwise, you'll forget and concatenate a user-supplied string; or someone else will copy your code without realising the caveat.

C#

using (SqlDataAdapter adapt = new SqlDataAdapter("Select * from dbo.SubMenuTable Where ParentId = @ParentId", con))
{
    adapt.SelectCommand.Parameters.AddWithValue("@ParentId", _parentId);
    ...
}