Yes, the reason your label is persisting its value on postback is because you are calling some method that populates the label's value on PageLoad event. Wrap this code inside
if(!IsPostBack)
{
}
On buttons click event clear the label's value
Protected Void Button1_Click(object sender, EventArgs e)
{
Label1.Text = "";
}
and if you want to populate the values again without the label persisting its value use:
Protected Void Button1_Click(object sender, EventArgs e)
{
Label1.Text = "";
}Hope it helps. If it doesn't work post your complete code.