Controls Value Is Not Updated Aspx.cs?

during page load itself textbox and dropdownlist is assigned values. when the values are changed later and button is clicked to pass these values to the next fn only the old value is send

protected void Page_Load(object sender, EventArgs e)
{
TextBox1.Text = "before";
ArrayList a = new ArrayList();
a.Add("b");
a.Add("a");
DropDownList1.DataSource = a;
DropDownList1.DataBind();
DropDownList1.SelectedValue = "b";
}

//now in form text box= "before" and droplist=b . if i change the value

abd click the button the new value is not passed

[code]....