Delete Data in ASP.Net C#

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;
using System.Data.SqlClient;
using System.IO;
using System.Configuration;

public partial class Delete_Users : System.Web.UI.Page {
    public SqlConnection koneksi;
    public SqlDataReader data_reader;
    public string koneksi_string;
    protected void Page_Load(object sender, EventArgs e) {
        if (!IsPostBack) {
            delete();
        }
    }
    void delete() {
        string users_id = Request.QueryString["id"].ToString();
        koneksi = new SqlConnection(ConfigurationManager.ConnectionStrings["koneksi_material"].ConnectionString);
        SqlCommand cmd = new SqlCommand("delete from t_users where id = '" + users_id + "'", koneksi);
        koneksi.Open();
        cmd.ExecuteNonQuery();
        koneksi.Close();
        Response.Redirect("View_Users.aspx");
    }
}