Implement Change password in ASP.Net using C#

how to make password change using asp c#

namespace Mob_del_dtls
{
    public partial class pswr : System.Web.UI.Page
    {
        string strConnString = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
        string str = null;
        SqlCommand com;
        byte up;  
        protected void Page_Load(object sender, EventArgs e)
        {           
            if (Session["FirstName"] == null)
                Response.Redirect("Index.aspx");
            else
            {
                String EmplooyeId = Session["emp_id"].ToString();
                Label2.Text = " " + EmplooyeId + "";
                String FirstName = Session["FirstName"].ToString();
                String LastName = Session["LastName"].ToString();
                String Department = Session["Department"].ToString();
                lbluserInfo.Text = "Department: " + Department + ".";
                Label1.Text = "Welcome " + FirstName + " " + LastName + ".";
            }
        }
        protected void btn_update_Click(object sender, EventArgs e)
        {
            SqlConnection con = new SqlConnection(strConnString);
            con.Open();
            str = "select * from emp_mast1 ";
            com = new SqlCommand(str, con);
            SqlDataReader reader = com.ExecuteReader();
            while (reader.Read())
            {
                if (txt_cpassword.Text == reader["Password"].ToString())
                {
                    up = 1;
                }
            }
            reader.Close();
            con.Close();
            if (up == 1)
            {
                con.Open();
                str = "update emp_mast1 set Password=@Password where emp_id='" + Label2 .Text+ "'";
                com = new SqlCommand(str, con);
                com.Parameters.Add(new SqlParameter("@Password", SqlDbType.VarChar, 50));
                com.Parameters["@Password"].Value = txt_cpassword.Text;
                com.ExecuteNonQuery();
                con.Close();
                lbl_msg.Text = "Password changed Successfully";
            }
            else
            {
                lbl_msg.Text = "Please enter correct Current password";
            }  
        }
    }
}