How to retrieve data from database and display it on label

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C#

ASP.NET

I'm working on the Registration page for Lucky Draw system.So the process for registration is user need to scan their barcode using usb barcode scanner. I stuck on that part which i cannot check the employee id on database after user scan or type in the textbox. I also want to display the employee name after scan the barcode.Can anyone give me some ideas/solution.

What I have tried:

Below are my code:

using System;  
using System.Collections.Generic;  
using System.Data;  
using System.Data.SqlClient;  
using System.IO;  
using System.Linq;  
using System.Web;  
using System.Web.UI;  
using System.Web.UI.WebControls;
public partial class Attendance : System.Web.UI.Page  
{  
    SqlCommand cmd = new SqlCommand();  
    SqlConnection con = new SqlConnection();  
    string str;  
    private string connectionString;  
  
    protected void Page_Load(object sender, EventArgs e)  
    {  
        con.ConnectionString = @"Data Source= (LocalDB)\MSSQLLocalDB; AttachDbFilename =   
          C:\Users\Nor  Asyraf  Mohd No\source\repos\LuckyDraw\LuckyDraw\App_Data\ticket.mdf;   
            Integrated Security = True";
        txtText.Focus();  
    }  
  
    protected void btnSave_Click(object sender, EventArgs e)  
    {  
        idcheck();  
        using (SqlConnection connection = new SqlConnection(connectionString))  
        {  
            using (SqlCommand command = connection.CreateCommand())  
            {  
                command.CommandText = "UPDATE EMPLOYEES SET Attendance = 'Present' WHERE EMP_ID = @id";  
                command.Parameters.AddWithValue("@id", txtText.Text);  
                connection.Open();  
  
                command.ExecuteNonQuery();  
  
                connection.Close();  
            }  
        }
    }  
  
public void idcheck()  
        {
        string query = "select EMP_ID from EMPLOYEES where EMP_ID='" + txtText.Text + "'";  
        SqlDataAdapter ada = new SqlDataAdapter(query, con);  
        DataTable dt = new DataTable();  
        ada.Fill(dt);  
        if (dt.Rows.Count > 0)  
        {  
            lblError.Text = dt.Rows[0]["EMP_NAME"].ToString();  
        }  
    }
    protected void Button1_Click1(object sender, EventArgs e)  
    {  
        Response.Redirect("Default.aspx");  
    }  
}