想要使用javascript显示消息框

Question

Hi everyone I have a web form in which I am having a button on clicking which data back up is being taken, I used the following javascript :

<script language="javascript" type="text/javascript">
   function showPleaseWait() {
       document.getElementById('PleaseWait').style.display = 'block';
   }
</script>

<asp:Button ID="btnTakebackup" runat="server" Text="Take Backup"  Enabled="true" 
   onMouseDown="showPleaseWait()" CausesValidation="false" />

<div id="PleaseWait" style="display: none;">"Please Wait Backup in Progress.."</div>

Hi I am using a button to take a back up.

Now I want to show a message in btnTakebackup_Click() event, whether Back up was successful or not. I used Response.Write("<script>alert('abcd');</script>"); in btnTakebackup_Click() event. But the problem is that I want to show the page also, which is not showing instead white background is showing.

Thanks in advance...

Answer 1

Do you really want it to be an alert? (You should know that they lock up the whole browser not just the tab your page is on), do your users really need to acknowledge the backup success by clicking ok or just be informed of it?...

I suggest you have a div on the page that says "Backup successful". The visibility of which can be set by a boolean property BackUpSuccess which you can set to true in the code behind you mention.

<div id="backUpSuccess" <%=BackUpSuccess ? "" : "style='display:none;'"%>>
    Backup was successfull
</div>

...you can style the div as you like in your .css file to get attention.

---

If you really do want an alert you could run some JavaScript on page load to check the content of a hidden input that you set server side in similar fashion...but running javascript on page load is tricky...unless your using jQuery and then you will know it's very easy.

Answer 2

To show a message box alert should be able to write out a new script to the response stream:

var script = 
    "<script type=\"javascript\">" +
    "alert(\"Backup in progress, don't go!\");" +
    "</script>"
Response.Write(script);

However much this is distasteful, I suppose it is sometimes "necessary".

Answer 3

You can add client side event handlers to ASP controls:

How to: Add Client Script Events to ASP.NET Web Server Controls

Cheers.

Answer 4

From your question, I understood that after clicking on the button, the data back up is happening, but the alert is not displaying as soon as you clicked the button.This is because you are calling the JavaScript in the button click event which will be fired only after all the code in the button click is executed.I suggest you to add a JavaScript function in the .aspx source page it self and call the JavaScript function as shown below:

        <script ...>
        function xyz()
        {
        alert('Please Wait');
        }
        </script>

    and in button declaration

        <asp:button id='btn_submit' runat="server" OnClientClick="return xyz();" />