page refresh question

here is my coding

 

: runat="server">

 

 

protected void Page_Load(object sender, EventArgs e)
{




}


protected void Button1_Click1(object sender, EventArgs e)
{
if (Page.IsPostBack && TextBox1.Text == "")
{
Response.Write("

please fill textbox

");
}
else if(Page.IsPostBack)
{
TextBox1.Text = "";

}
if (Page.IsPostBack)
{
Response.Write("data sened to server is "+TextBox1.Text);
}

}
} 

 

i want that if i refresh the page by pressing F5 all data in the textbox and  the  server side message should disappear.how could i do that