how do I call the asp postback of button inside datalist?

Question

How can I get to the javascript postback event call for an asp button?

    <ItemTemplate>
        <asp:Button id="btnTest" runat="server" 
                    Text="button" OnClientClick="
            customAsyncConfirmDialog(function (isconfirmed)
            {
                if(isconfirmed)
                {
                    //call this buttons postback event
                    <%# Page.ClientScript.GetPostBackEventReference(new PostBackOptions(Container.FindControl("btnTest")))%>;
                }
            });return false;
            "/>
    </ItemTemplate>
</asp:DataList>

Update: The customAsyncConfirmDialog is an asynchronous function that does not block the javascript to wait for a response.

Answer 1

No need to do that. Just return true and the postback handler will be hit. Ex:

<ItemTemplate>
    <asp:Button id="btnTest" runat="server" 
                Text="button" OnClientClick="
        customConfirmDialog(function (isconfirmed)
        {
            return isconfirmed;                
        });
        "/>
</ItemTemplate>

I'm having trouble accessing what I wrote earlier, but here's a quick example based on what you wrote in your other answer. You might need to change a few things but you should get the idea:

window.confirm = function(question, ok, cancel) {
    var defer = $.Deferred();
    ok = ok || 'OK'; //setup text for the confirmation
    cancel = cancel || 'Cancel';

    $(document).ready(function() {

        $('#customMessage').text(question);
         var btnOk = $('#btnCustomOK');
         var btnCancel = $('#btnCustomCancel');
         btnOk.val(ok);
         btnCancel.val(cancel);

        btnOk.unbind("click"); //prevents chaining of events if multiple confirms are used
        btnCancel.unbind("click"); 
        btnOk.click(function() {
            $('#MyConfirm').hide();
            defer.resolve(true); //gets passed as isconfirmed=true
            return false; //prevent postback
        });

        btnCancel.click(function() {
            $('#MyConfirm').hide();
            defer.resolve(false);
            return false; //prevents postback
        });        

        $('#MyConfirm').show();                
        btnOk.focus();
    });
    return defer.promise();
}

Then to use:

<asp:Button id="btnTest" runat="server" Text="button"
  OnClientClick="confirm('My Message blah blah').then(//this runs after ok/cancel is clicked, thanks to defer.resolve() and defer.promise().
function(isConfirmed) {
 if (isConfirmed)
 __doPostBack(source.id,'');
}); return false;//return false here to prevent the initial postback from occurring"/>
    </ItemTemplate>

the 'source.id' part isn't exactly right, but the part with the promises should help you out.

Answer 2

I was able to get it to call the postback with the following:

<script type="text/javascript">
    function customConfirmDialog(sourceButton, callback) {
        setTimeout(function () { callback(sourceButton, true); }, 1);
        return false;
    }
</script>

<asp:DataList ID="dlTest" runat="server">
    <ItemTemplate>
        <%# Page.ClientScript.GetPostBackEventReference(new PostBackOptions(Container.FindControl("btnTest")))%>;
        <asp:LinkButton runat="server" ID="neededfor__dopostbackgenerationforsomereason"></asp:LinkButton>
        <asp:Button id="btnTest" runat="server" 
                    Text="button"
            OnClick="btnTest_OnClick"
                    OnClientClick="
                return customConfirmDialog(this,function (sourceButton, isconfirmed)
                {
                    if(isconfirmed)
                    {
                        //call this button's postback event
                        __doPostBack(sourceButton.name,'');
                    }
                }); 
            "/>
    </ItemTemplate>
</asp:DataList>

I had to add a linkbutton to get __doPostBack to generate, not sure why the ASP:Button alone didn't trigger that. I still couldn't use the Page.ClientScript.GetPostBackEventReference in the onClientClick function.

Final note, you need to call __doPostBack with sourceButton.name rather that sourceButton.id to trigger the correct server side event.