สอบถามการเคลียร์ค่า document.forms[0].appendChild ASP.net

function Confirm() {
           var confirm_value = document.createElement("INPUT");
           confirm_value.type = "hidden";
           confirm_value.name = "confirm_value";
           if (confirm("Do you want to save data?")) {
               confirm_value.value = "Yes";
           } else {
               confirm_value.value = "No";
           }
           document.forms[0].appendChild(confirm_value);
           }

 Private Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim confirmValue As String = Request.Form("confirm_value")
        MsgBox(Request.Form("confirm_value"))
        If confirmValue = "Yes" Then
            DisplayAJAXMessage(Page, "Yes")
        ElseIf confirmValue = "No" Then
            DisplayAJAXMessage(Page, "No")
        End If
    End Sub