Hi Corobori,
Refer below example.
HTML
<asp:RadioButtonList ID="opt" runat="server">
    <asp:ListItem Selected="True" Value="0">OK</asp:ListItem>
    <asp:ListItem Value="1">Raise error</asp:ListItem>
    <asp:ListItem Value="2">Cause failure</asp:ListItem>
</asp:RadioButtonList>
<asp:Button ID="Button1" runat="server" OnClientClick="CallMyFunction();" Text="Button" />
<script src="https://code.jquery.com/jquery-3.6.0.min.js" integrity="sha256-/xUj+3OJU5yExlq6GSYGSHk7tPXikynS7ogEvDej/m4=" crossorigin="anonymous"></script>
<script type="text/javascript">
    var pageUrl = '<%=ResolveUrl("~/Default.aspx")%>'
    function CallMyFunction() {
        action = $('#opt input:checked').val();
        $.ajax({
            type: "POST",
            url: pageUrl + '/CallMyCode',
            data: '{action: ' + action + '}',
            contentType: "application/json; charset=utf-8",
            dataType: "json",
            success: function (response, xhr, status) {
                if (response.d == "0") {
                    alert("success");
                } else if (response.d == "1") {
                    handleError(xhr, status, '');
                } else if (response.d == "2") {
                    handlefailure(xhr, status, '');
                }
            },
            error: handleError,
            failure: handlefailure
        });
    }
    function handleError(xhr, status, error) {
        alert("error");
    }
    function handlefailure(xhr, status, error) {
        alert("failure");
    }
</script>
Code
C#
[System.Web.Services.WebMethod()]
public static string CallMyCode(int action)
{
    if (action == 0)
    {
        return "0"; 
    }
    else if (action == 1)
    {
        return "1";
    }
    else
    {
        return "2";
    }
}
VB.Net
<System.Web.Services.WebMethod()>
Public Shared Function CallMyCode(ByVal action As Integer) As String
    If action = 0 Then
        Return "0"
    ElseIf action = 1 Then
        Return "1"
    Else
        Return "2"
    End If
End Function
Screenshot
