ASP.Net: GridView control and combobox woes

I've got a GridView control and Combobox control that are both successfully populated in my Page_Load event (within a block that checks for IsPostBack == false).

I've got an empty button 'btnClick' event handler which will reload the page when clicked. Both the GridView and Combobox controls have their EnableViewState property set to True. The behaviour I was expecting and hoping for was:

1. Page will reload with the GridView control still populated.
2. Page will reload with Combobox still populated and the item selected by the user still set as the selected item.

Unfortunately, the behaviour I'm getting is as follows:

1. GridView control is now empty and shows no data.
2. Combobox is now empty.

Code as follows:

public MyPage()
{
    this.Load += new EventHandler(Page_Load);
}

protected void Page_Load(object sender, EventArgs e)
{
    if (IsPostBack == false)
   开发者_如何转开发 {
        DataAccessObj daObj = new DataAccessObj();

        foreach (DataRow dataRow in daObj.GetAllData())
        {
            ListItem listItem = new ListItem(dataRow.ToString(), dataRow.Id.ToString());
            myCombobox.Items.Add(listItem);
        }

        IncidentGrid.DataSource = daObj.GetIncidentsByReportedById(0);
        IncidentGrid.DataBind();
    }
}

protected void btnSubmit_Click(object sender, EventArgs e)
{
    // Do nothing
}

What I would like to do is allow the user to select an item from the Combobox. Upon clicking Submit, the GridView would be repopulated (based upon the selected item). The Combobox will remain populated and show the last selected item.

Can someone help explain where I might be going wrong? TIA

When you click your button, the page is posted back, in your page load, if it is a postback you need to databind the grid appropriately you need to add a condition to your page load event like

Firstly on your btn_click, you need to store the id selected with something like:

if (myCombobox.SelectedItem != null)
    {
        if (int.TryParse(myCombobox.SelectedItem.Value, out reportedById) == false)
        {
            reportedById = 0;
            ViewState["reportedById"] = reportedById; // Need to remember which one was selected
        }
    }

Then On your Post Back

    else (IsPostBack)
    {
       if (ViewState["reportedById"]) != null)
    {
       IncidentGrid.DataSource = daObj.GetIncidentsByReportedById(Convert.ToInt32(ViewState["reportedById"]));
       IncidentGrid.DataBind();
myCombobox.SelectedItem.Value = ViewState["reportedById"].ToString(); // set combo

    }

        else
        {
         IncidentGrid.DataSource = daObj.GetIncidentsByReportedById(0);
        IncidentGrid.DataBind();

            }
    }