C# Bits: GridView Pager Size

For the motivation for this article see Retain "Number of Records" to display in GridView by defyant_2004 where the idea is, if I change the the pager size in the list page go to another page and then return to the ListPage chances are I still want the pager size to be the same.

So here the simple solution:

protected void DropDownListPageSize_SelectedIndexChanged(object sender, EventArgs e)
{
    if (_gridView == null)
        return;

    DropDownList dropdownlistpagersize = (DropDownList)sender;
    _gridView.PageSize = Convert.ToInt32(dropdownlistpagersize.SelectedValue);

    // save pager size
    if (Session["DD_PagerSize"] != null)
        Session["DD_PagerSize"] = _gridView.PageSize.ToString();
    else
        Session.Add("DD_PagerSize", _gridView.PageSize.ToString());

    int pageindex = _gridView.PageIndex;
    _gridView.DataBind();
    if (_gridView.PageIndex != pageindex)
    {
        //if page index changed it means the previous page was not valid and was adjusted. Rebind to fill control with adjusted page
        _gridView.DataBind();
    }
}

Listing 1 – the DropDownListPageSize_SelectedIndexChanged event for the GridViewPager

protected void Page_Load(object sender, EventArgs e)
{
    Control c = Parent;
    while (c != null)
    {
        if (c is GridView)
        {
            _gridView = (GridView)c;

            // if pager size saved then restore it
            var pagerSize = Session["DD_PagerSize"];
            if (_gridView != null && pagerSize != null)
            {
                _gridView.PageSize = Convert.ToInt32(pagerSize);
            }

            break;
        }
        c = c.Parent;
    }
}

Listing 2 – the Page_Load event for the GridViewPager

Listings 1 & 2 are the minimum we need to do to get this functionality see the Forum post for a VB example.

But my thoughts turn to what if I want a different setting for different tables?

So here it is:

Add a private variable to the user control

public partial class GridViewPager : System.Web.UI.UserControl
{
    private GridView _gridView;
    private MetaTable _table;

Listing 3 – global _table variable

protected void Page_Load(object sender, EventArgs e)
{
    Control c = Parent;
    while (c != null)
    {
        if (c is GridView)
        {
            _gridView = (GridView)c;

            // if pager size saved then restore it
            var GridDataSource = _gridView.FindDataSourceControl();
            _table = GridDataSource.GetTable();

            var pagerSize = Session[_table.Name + "_PagerSize"];
            if (_gridView != null && pagerSize != null)
            {
                _gridView.PageSize = Convert.ToInt32(pagerSize);
            }

            break;
        }
        c = c.Parent;
    }
}

Listing 4 – Page_Load

In Listing 4 we get the GridViews DataSource and then find out which table we are working on, then we create a session variable to hold the pager size for this table by combining the table name with “_PagerSize” string.

protected void DropDownListPageSize_SelectedIndexChanged(object sender, EventArgs e)
{
    if (_gridView == null)
        return;

    DropDownList dropdownlistpagersize = (DropDownList)sender;
    _gridView.PageSize = Convert.ToInt32(dropdownlistpagersize.SelectedValue);

    // save pager size
    if (Session[_table.Name + "_PagerSize"] != null)
        Session[_table.Name + "_PagerSize"] = _gridView.PageSize.ToString();
    else
        Session.Add(_table.Name + "_PagerSize", _gridView.PageSize.ToString());

    int pageindex = _gridView.PageIndex;
    _gridView.DataBind();
    if (_gridView.PageIndex != pageindex)
    {
        // if page index changed it means the previous page was page 
        // not valid and was adjusted. Rebind to fill control with adjusted
        _gridView.DataBind();
    }
}