ASP.NET

protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            if (Request.QueryString["id"] != null)
            {
                dataEmp = empleado.getEmployeeById(Request.QueryString["id"]);
                DetailsView1.DataSource = this.dataEmp;
                DetailsView1.DataBind();
            }
            else
            {
                dataEmp = empleado.getEmployeeById("noId");
                DetailsView1.DefaultMode = DetailsViewMode.Insert;
                DetailsView1.DataSource = this.dataEmp;
                DetailsView1.DataBind();

                btnNew_Click(sender, e); //works if called here
            }
        }
    }

protected void btnNew_Click(object sender, EventArgs e)//does not worked when user clicks on button
    {
        DetailsView1.ChangeMode(DetailsViewMode.Insert);
        
        ((TextBox)DetailsView1.Rows[0].FindControl("txtID")).Text = generateKey();
       
        btnInsert.Visible = true;
        btnNew.Visible = false;
        Response.Write("clear form");
        
    }
private string generateKey()
    {   
        Random numb = new Random();
        string generatedKey =   ((char)((short) 'A' + numb.Next(26))).ToString() + 
                            ((char)((short) 'A' + numb.Next(26))).ToString() + 
                            ((char)((short) 'A' + numb.Next(26))).ToString() + 
                            ((char)((short) '1' + numb.Next(8))).ToString() + 
                            ((char)((short) '0' + numb.Next(9))).ToString() + 
                            ((char)((short) '0' + numb.Next(9))).ToString() +
                            ((char)((short) '0' + numb.Next(9))).ToString() +
                            ((char)((short) '0' + numb.Next(9))).ToString();
        if (numb.Next(1, 2) == 1)
            generatedKey += 'F';
        else
            generatedKey += 'M';

        return generatedKey;
    }