WebMethod not working when remove static key word using C# in ASP.Net

i tried like this code it works.only if the methos is static.

if i remove static for method it not invokes.  what is the reason can u please tell me if u know.

in that method it not accepts asp.net controls .in that code if i remove the comment for "label1.text".it shows error  it not exists in current context. 

how to handle that label1.text in that method if u know can please tell me sir.

<script type="text/javascript">
    $(function () {
        $("[id*=Button1]").click(function () {
            //alert('ok');
            var obj = {};
            obj.N1 = $.trim($("[id*=TextBox1]").val());
            obj.N2 = $.trim($("[id*=TextBox2]").val());
            $.ajax({
                type: "POST",
                url: "WebForm1.aspx/Button",
                data: JSON.stringify(obj),
                contentType: "application/json; charset=utf-8",
                dataType: "json",
                success: function (r) {
                    // for laBel
                    $("#vv").text(r.d);
 
                    //for textBox
                    //$("#vv").val(r.d);
 
                    //alert(r.d);
                }
            });
            return false;
        });
    });
</script>
<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
<asp:TextBox ID="TextBox2" runat="server"></asp:TextBox>
<asp:Button ID="Button1" runat="server"  Text="ADD" />

[System.Web.Services.WebMethod]
 public static string Button(string N1, string N2)
 {
     WebService1 aa = new WebService1();
     int a, z;
     a = Convert.ToInt32(N1);
     z = Convert.ToInt32(N2);
     int result1 = aa.add(a,z);
     
     //Label1.Text = result1.ToString();
     return result1.ToString();
 }