在 C# windows 表格中的树视图中面临问题，详情如下：

Question

Whenever I tried to get the value from treeview in which I get the data from database on Get Data button and try to display it on datagridview by checking the checkbox of treeview node it will not display the details of that node in datagridview on Search button.

Treeview after getting the data from Database on Get Data Button:

So, I want now is that whenever I check the treeview node and then click on Search button it must show all details of that node in datagridview .

My Code of this Winform :

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Data.SqlClient;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace My_Work
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Get_Data_Click(object sender, EventArgs e)
        {
            string conStr = "Integrated Security=SSPI;Persist Security Info=False;Initial Catalog=Data;Data Source=MY-PC";
            SqlConnection con = new SqlConnection(conStr);
            con.Open();
            string query = "select ItemNo,UnitePrice from Product_Item";
            SqlCommand cmd = new SqlCommand(query, con);
            SqlDataReader sdr = cmd.ExecuteReader();
            while (sdr.Read())
            {
                TreeNode n = new TreeNode(sdr["ItemNo"].ToString());
                treeView1.Nodes.Add(n);
                n.Nodes.Add(sdr["UnitePrice"].ToString());
            }
            con.Close();
        }

        private void treeView1_NodeMouseClick(object sender, TreeNodeMouseClickEventArgs e)
        {
            string conStr = "Integrated Security=SSPI;Persist Security Info=False;Initial Catalog=Data;Data Source=MY-PC";
            SqlConnection con = new SqlConnection(conStr);
            con.Open();
            string nodeName = e.Node.ToString().Replace("TreeNode: ", string.Empty);
            if (e.Node.Parent != null)
            {
                string q = "select * from Product_Item where UnitePrice='" + nodeName + "'";
                SqlCommand cmd = new SqlCommand(q, con);
                SqlDataAdapter sda = new SqlDataAdapter(cmd);
                DataTable dt = new DataTable();
                sda.Fill(dt);
                con.Close();
                dataGridView1.DataSource = dt;
            }
        }

        private void Search_Click(object sender, EventArgs e)
        {
            string conStr = "Integrated Security=SSPI;Persist Security Info=False;Initial Catalog=Data;Data Source=MY-PC";
            SqlConnection con = new SqlConnection(conStr);
            con.Open();
            if(treeView1.CheckBoxes == true)
            {
                string nodeCheck = treeView1.CheckBoxes.ToString();
                string q = "select * from Product_Item where ItemNo='" + nodeCheck + "'";
                SqlCommand cmd = new SqlCommand(q, con);
                SqlDataAdapter sda = new SqlDataAdapter(cmd);
                DataTable dt = new DataTable();
                sda.Fill(dt);
                con.Close();
                dataGridView1.DataSource = dt;
            }
        }
    }
}

This is the code in which I want to get the details of check node but I cannot get the details of that node.

private void Search_Click(object sender, EventArgs e)
{
        string conStr = "Integrated Security=SSPI;Persist Security Info=False;Initial Catalog=Data;Data Source=MY-PC";
        SqlConnection con = new SqlConnection(conStr);
        con.Open();
        if(treeView1.CheckBoxes == true)
        {
            string nodeCheck = treeView1.CheckBoxes.ToString();
            string q = "select * from Product_Item where ItemNo='" + nodeCheck + "'";
            SqlCommand cmd = new SqlCommand(q, con);
            SqlDataAdapter sda = new SqlDataAdapter(cmd);
            DataTable dt = new DataTable();
            sda.Fill(dt);
            con.Close();
            dataGridView1.DataSource = dt;
        }
}

Database Table Product_Item :

Answer 1

The TreeView.CheckBoxes Property returns a Boolean telling you whether the treeview displays checkboxes. You cannot get the required SQL condition out of it, but you can get the item numbers of the checked items with

var itemNums = new List<string>();
foreach (TreeNode node in treeView1.Nodes)
{
    if (node.Checked) {
        itemNums.Add(node.Text);
    }
}

Now, you must create a SQL condition from this list. Assuming that these numbers are stored in a int column, we can create a list of numbers with

string numList = String.Join(", ", itemNums);

and then use this to build the SQL statement:

string sql = "SELECT * FROM Product_Item WHERE ItemNo IN (" + numList  + ")";

If, however, the item numbers are stored in a text column, then we must write

string numList = String.Join("', '", itemNums);
string sql = "SELECT * FROM Product_Item WHERE ItemNo IN ('" + numList  + "')";

This produces conditions looking like WHERE ItemNo IN (1, 7, 9) or
WHERE ItemNo IN ('1', '7', '9') .