Cannot to prompt message and close pop-up after saving data

Hello,

Program description:
When user input data and click Add button, the current add button is disabled and it trigger another hidden add button event to save data to database
After data was saved, it will prompt "save successfully" message and close the current pop-up window
Problem: After data was saved, it can't prompt message and close the pop-up
------------------------------------------------
Here is my code:
1. Function to hide hidden add button and add onclick script to add button in Page_Load event public void SetForm() {   btnHiddenSave.Attributes.Add("style", "display:none");   btnSave.Attributes.Add("onclick", "document.getElementById('" + btnSave.ClientID +   "').disabled=true;document.getElementById('" + btnHiddenSave.ClientID + "').c ...