How to add and delete controls dynamically on runtime ?

Adding code is working proper but how to delete ?

 

%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default2.aspx.cs" Inherits="Default2" %>

 

 

protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
ViewState["AddControl"] = 1;
}
}
protected void add_Click(object sender, EventArgs e)
{
add_button(Convert.ToInt32(ViewState["AddControl"]));
}

protected void add_button(int i)
{
for (int j = 0; j < i; j++)
{
TextBox textbox_foradd = new TextBox();
textbox_foradd.ID = "textadd" + (j + 1).ToString();
PlaceHolder1.Controls.Add(textbox_foradd);

Button btn = new Button();
btn.Text = "X";

textbox_foradd.ID = "btn" + (j + 1).ToString();
PlaceHolder1.Controls.Add(btn);
}
ViewState["AddControl"] = i + 1;
}