How do you use an UpdatePanel properly?

I have an UpdatePanel with some checkboxes in it. I check them, and hit my Save button, but that causes the UpdatePanel to postback (refresh)开发者_如何学Go and sets them all back to blank. The re-drawing method runs before the button code.

What is the correct way to have an UpdatePanel with checkboxes in that you can manipulate?

Example of code:

<asp:UpdatePanel runat="server" UpdateMode="Conditional" ID="updatePanel1">
    <ContentTemplate>
        <asp:CheckBox runat="server" ID="myCheckBox" Caption="CheckBox"/>
        <asp:Button runat="server" ID="saveButton" 
                   Caption="Save" OnClick="SaveButtonClick"/>
    </ContentTemplate>    
    <Triggers>
        <asp:AsyncPostBackTrigger ControlID="saveButton" EventName="Click" />        
    </Triggers>
</asp:UpdatePanel>

Make sure that:

1. UpdateMode of UpdatePanel is Conditional
2. SaveButton contained in Triggers-section as ControlID of AsyncPostBackTrigger

Your code behind should look like:

if(!page.ispostback)
{
   re-drawing();
}

As when you hit Save button your re-drawing() method is called and it again refreshes your checkboxes. Asynchronous postback behaves and hit to page method the same as full postback, but refreshes the values in any updatepanels.

Also check this URL http://ajax.net-tutorials.com/controls/updatepanel-control/

Make sure the Save button is inside the Update Panel, for a start, and if not, that is designated as a Trigger for the Update Panel, in the <Triggers> section of the Update Panel.

<asp:UpdatePanel ID="MyControlPanel" runat="server" UpdateMode="Conditional">
    <Triggers>
        <asp:AsyncPostBackTrigger ControlID="SaveButton" />
    </Triggers>
    <ContentTemplate> ...

Can you show some code for your UpdatePanel?

If you use server controls to render checkboxes you should add EnableViewState="true" attribute to these controls and update panel.

If you have checkboxes that are not server controls, then remove them from update panel, include only server controls inside. This leads to keeping several updates panel on a page that's usually not a big issue.

Add a ScriptManager object to your page if you do not have one. Set EnablePartialRendering="true". Put your UpdatePanel anywhere else on the page and place the content you want ajaxified within a tag within your UpdatePanel.