ASP.Net : DataPager Control always a step behind with paging

Question

Take the following example...a page with a ListView and a DataPager used for paging the data of the ListView:

Code Behind:

protected void Page_Load(object sender, EventArgs e)
{
    MyList.DataSource = GetSomeList();
    MyList.DataBind();
}

Source:

<asp:ListView ID="MyList" runat="server">
    <% //LayoutTemplate and ItemTemplate removed for the example %>
</asp:ListView>

<asp:DataPager ID="ListPager" PagedControlID="MyList" runat="server" PageSize="10">
    <Fields>
        <asp:NumericPagerField  />
    </Fields>
</asp:DataPager>

The problem with the DataPager is that it is always a step-behind with the binding.

For example, when the page loads it's on page number 1. Then when you click on page 3, it stays on page 1 after the postback. Then you click on page 5, and after the postback it finds itself on page 3...and after that you click on page 6, and it finds itself on page 5...and so on and so forth.

Why isn't the paging working as expected?

Answer 1

Solution

The problem is due to the binding occuring on the Page_Load event.

For this to work as expected, the binding needs to happen in the DataPager's OnPreRender event, not in the Page_Load.

Source:

<asp:DataPager ID="ListPager" PagedControlID="MyList" runat="server" PageSize="10"
    OnPreRender="ListPager_PreRender">

<Fields>
        <asp:NumericPagerField  />
    </Fields>
</asp:DataPager>

Code Behind:

protected void Page_Load(object sender, EventArgs e)
{
    //Binding code moved from Page_Load
    //to the ListView's PreRender event
}

protected void ListPager_PreRender(object sender, EventArgs e)
{
    MyList.DataSource = GetSomeList();
    MyList.DataBind();    
}