Hi,

I am testing a simple scenario with a GridView bound to a ObjectDataSource at desgin time - by using the DataSourceId attribute of GridView.

As soon as the page loads, it automatically triggers the Select method of the ObjectDataSource. Being a long query, it takes a while for the page to load.  On other pages of the app, I have a button that triggers the Update Panel postback. I show a progress bar in the async request.

I do not want an unnecessary button click event to trigger the UpdatePanel async postback as there is no need of a button on this page.

 And I do not want to manually bind the data source to the GridView.

 How do I trigger the UpdatePanel async postback on the initial page load? Any ideas will be greatly appreciated.

Here's my code:

       <asp:UpdatePanel ID="UpdatePanel1" runat="server" UpdateMode="Always" >
            <ContentTemplate>
                <div id="divGridView">
                    <asp:GridView  ID="GridView1" SkinID="epwGridView" runat="server" DataSourceID="odsLocation">
                        <Columns>
                            <asp:BoundField HeaderText="Location"  DataField="LOCATION_CODE" SortExpression="LOCATION_CODE" ItemStyle-Width="100"/>
                            <asp:BoundField HeaderText="Description" DataField="DESCRIPTION" SortExpression="DESCRIPTION" ItemStyle-Width="200" ReadOnly="true" />
                        </Columns>
                    </asp:GridView>
                </div>
            </ContentTemplate>
            <Triggers>

            </Triggers>
        </asp:UpdatePanel>
    </div>    
    <asp:ObjectDataSource ID="odsLocation" runat="server"  
        SelectMethod="GetLocations" 
        TypeName="EPWWEB.BLL.Maintenance.LocationBL" >
    </asp:ObjectDataSource>

 Thanks

hpdotnet 

If you change your UpdatePanel's UpdateMode to Conditional and then in your Page_Load call the UpdatePanel1.Update() if its not a postback.

Doesn't work. It does not trigger the async postback.

I tried putting the ObjectDataSource inside the UpdatePanel too. Didn't help.

I must be missing something simple. I just need the GridView to be populated asynchoronusly on the initial page load. 

I have seen this on so many ajax-enabled pages. Do they all use a dummy button click/postback event ?

 Thanks

hpdotnet 

try using AJAX timer control like this.

//set your updatepanel mode to "conditional"
<asp:GridView  ID="GridView1" SkinID="epwGridView" runat="server">
                        <Columns>
                            <asp:BoundField HeaderText="Location"  DataField="LOCATION_CODE" SortExpression="LOCATION_CODE" ItemStyle-Width="100"/>

<asp:BoundField HeaderText="Description" DataField="DESCRIPTION" SortExpression="DESCRIPTION" ItemStyle-Width="200" ReadOnly="true" />
                        </Columns>
</asp:GridView>

//don't set DataSourceID="odsLocation" initially
//place a timer control

<asp:Timer runat="server" id="UpdateTimer" interval="1000" ontick="Timer1_Tick" />
// interval in miliseconds

//on timer1 tick
protected void Timer1_Tick(object sender, EventArgs e)
{
      GridView1.DataSourceId = "odsLocation";
      GridView1.DataBind();
      UpdatePanel1.Update();
      Timer1.Enabled=false; // disable timer as we don't want to repeat this task
}

hope this helps, let me know in case of any problems.

 Hi aadreja,

Thanks for your reply. I cannot use that option because I need to specify the DataSourceId in the GridView at design time. This GridView is going to use the ObjectDataSource for editing, paging etc. Manually binding it is creating complications in more places.

 Do you know in what Page/Control event does the databinding occur.

I am thinking on these lines -

Check if the databinding event is async or not. If not, then cancel it and issue an async request, by calling UpdatePanel.Update(); . Will that work? Or any other ideas?

Thanks

hpdotnet 

Ok its simple.

Don't change DataSourceId

write this code OnSelecting of object datasource

protected void Timer1_Tick(object sender, EventArgs e)
{
      GridView1.DataBind();
      UpdatePanel1.Update();
      Timer1.Enabled=false; // disable timer as we don't want to repeat this task
}

//in aspx

<asp:ObjectDataSource ID="odsLocation" runat="server" SelectMethod="GetLocations"
   TypeName="EPWWEB.BLL.Maintenance.LocationBL" OnSelecting="odsLocation_Selecting">
</asp:ObjectDataSource>

let me know how it goes.

 Hi Ritesh,

Thanks for your idea. It works. I still have to play with the timer interval setting  but the concept works.

The main trick was to cancel the ODS binding in its OnSelecting event. I am debating between using an invisible button and timer. I feel Timers can throw up surprises.

 Here's the code:

       <asp:UpdatePanel ID="UpdatePanel1" runat="server" UpdateMode="Conditional">
            <ContentTemplate>
                <div id="divGridView">
                    <epw:EpwGridView  ID="GridView1" SkinID="epwGridView" runat="server" DataSourceID="odsLocation" EpwSessionId="LocationBL" EpwEnableEditing="true" >
                        <Columns>
                            <asp:BoundField HeaderText="Description" DataField="DESCRIPTION" SortExpression="DESCRIPTION" ItemStyle-Width="200" />
                        </Columns>
                    </epw:EpwGridView>
                </div>
                <asp:Timer runat="server" id="Timer1" Interval="3000" Enabled="false" OnTick="Timer1_Tick"/>       
            </ContentTemplate>
        </asp:UpdatePanel>
        <asp:ObjectDataSource ID="odsLocation" runat="server"  
            SelectMethod="GetLocations" UpdateMethod="UpdateLocation" OnSelecting="odsLocation_Selecting"
            TypeName="EPWWEB.BLL.Maintenance.LocationBL" >
            <UpdateParameters>
                <asp:Parameter Name="DESCRIPTION" Type="String" />
            </UpdateParameters>
        </asp:ObjectDataSource> 

    protected void Page_Load(object sender, EventArgs e)
    {
        if (!Page.IsPostBack)
        {
            Timer1.Enabled = true;
        }
    }

    protected void Timer1_Tick(object sender, EventArgs e)
    {
        if (Page.IsPostBack)
        {
            GridView1.DataBind();
        }
        Timer1.Enabled = false; // disable timer as we don't want to repeat this task
    }

    protected void odsLocation_Selecting(object sender, ObjectDataSourceSelectingEventArgs e)
    {
        if (!IsPostBack)
        {
            e.Cancel = true; //cancel selecting when page is loaded first time
            GridView1.EmptyDataText = "";
        }       
    }