problem in postback

[aftabShaikh]

Hi all
i have implemented a small application in which a button is placed named addRow when user clicks tht button a row is added in a grid view,whever user clicks it row will be added to the existing gridview i have done this with the following code now the problem is when i refresh the page the row is added or when i click any server control the row is also added bt i dont want this i just want the row shud be added when the button name addRow is clicked only.
any help will be greatly appreciated.thanks in advance

protected void Page_Load(object sender, EventArgs e)
    {
        if (!Page.IsPostBack)
            Session["dt"] = null;
 
    }
    protected override void OnPreInit(EventArgs e)
    {
        base.OnPreInit(e);                                    
            if (Request.Form["hf"] == "true")
                addGVRow();
        hf.Value = string.Empty;
    }
 
 
    private void addGVRow()
    {
        DataTable dt = (DataTable)Session["dt"];
        int counter = 0;
        if (dt == null)
        {
            dt = new DataTable();
            dt.Columns.Add("seq");
        }
        else
            counter = dt.Rows.Count;
        DataRow dr = dt.NewRow();
        dr[0] = counter + 1;
        dt.Rows.Add(dr);
        gv.DataSource = dt;
        gv.DataBind();
        Session["dt"] = dt;
    }

and on aspx page for the button
<asp:Button ID="btn" runat="server" Text="Add" OnClientClick="javascript:document.getElementById( 'hf').value='true';return true;" />