How send password to authenticate user

Question

How to make forget password where i want to recover password by email.

 

here is my code but its not working.

Connection c = new Connection();
   protected void btnPassword_Click(object sender, EventArgs e)
   {
       string userId = "";
       string email = "";
       string password ="";

       using (SqlConnection con = new SqlConnection(c.GetConnectionString()))
       {
           using (SqlCommand cmd = new SqlCommand("SELECT * FROM User_login WHERE userId = @user"))
           {
               cmd.Parameters.AddWithValue("@user", txtUser.Text.Trim());
               cmd.Connection = con;
               con.Open();
               using (SqlDataReader dr = cmd.ExecuteReader())
               {
                   if (dr.Read())
                   {
                       userId = dr["userId"].ToString();
                       email = dr["email"].ToString();
                       password = dr["Password"].ToString();
                   }
               }
               con.Close();
           }
       }
       if (!string.IsNullOrEmpty(password))
       {
           MailMessage mm = new MailMessage("[email protected]",email);
           mm.Subject = "Password Recovery";
           mm.Body = string.Format("Hi {0},<br /><br />Your password is {1}.<br /><br />Thank You.", userId, password);
           mm.IsBodyHtml = true;
           SmtpClient smtp = new SmtpClient();
           smtp.Host = "smtp.gmail.com";
           smtp.EnableSsl = true;
           NetworkCredential NetworkCred = new NetworkCredential();
           NetworkCred.UserName = "[email protected]";
           NetworkCred.Password = "*****";
           smtp.UseDefaultCredentials = true;
           smtp.Credentials = NetworkCred;
           smtp.Port = 587;
           smtp.Send(mm);
           er.Visible = true;
           ltrError.Text = "Password has been sent to your email address.";
       }
       else
       {
           er.Visible = true;
           ltrError.Text = "This email address does not match our records.";
       }
   }