ASP.NET

<br />
public partial class _Default : System.Web.UI.Page <br />
{<br />
    public string strSelected;<br />
<br />
    protected void Page_Load(object sender, EventArgs e)<br />
    {<br />
        if (!Page.IsPostBack) <br />
            strSelected = "*";<br />
<br />
        String sConStr = "Provider=Microsoft.Jet.OLEDB.4.0;" +<br />
            "Data Source=" + Server.MapPath ("ExcelData.xls") + ";" +<br />
            "Extended Properties=Excel 8.0;";<br />
        OleDbConnection objConn = new OleDbConnection (sConStr);<br />
        objConn.Open ();<br />
        <br />
        OleDbCommand objCmdSelect = new OleDbCommand ("SELECT " + strSelected + " FROM myRange1", objConn);<br />
        OleDbCommand objCmdSelectFirstname = new OleDbCommand ("SELECT Firstname FROM myRange1", objConn);<br />
        OleDbCommand objCmdSelectLastname = new OleDbCommand ("SELECT Lastname FROM myRange1", objConn);<br />
        OleDbDataAdapter objAdapter1 = new OleDbDataAdapter ();<br />
        objAdapter1.SelectCommand = objCmdSelect;<br />
        DataSet objDataset1 = new DataSet ();<br />
        objAdapter1.Fill (objDataset1, "XLData");<br />
        GridView1.DataSource = objDataset1.Tables[0].DefaultView;<br />
        GridView1.DataBind ();<br />
<br />
        objConn.Close ();<br />
    }<br />
<br />
    protected void lbQuery_SelectedIndexChanged (object sender, EventArgs e) {<br />
        switch (lbQuery.SelectedValue) {<br />
            case "firstName":<br />
                lblSelected.Text = "First name query selected.";<br />
                strSelected = "Firstname";<br />
                break;<br />
            case "lastName":<br />
                lblSelected.Text = "Last name query selected.";<br />
                strSelected = "Lastname";<br />
                break;<br />
            case "entireRange":<br />
                lblSelected.Text = "Entire range query selected.";<br />
                strSelected = "*";<br />
                break;<br />
            default:<br />
                lblSelected.Text = "Select query type above.";<br />
                break;<br />
        }<br />
    }<br />
}

if (Page.IsPostBack)
{
    if (something == true)
    {
	   DO SOMETHING TO CANCEL THE POSTBACK
    }
}