JSON and ASP.NET WebMethod not firing server side method

I'm trying to pass parameters to my code behind with WebMethod.

I'm reaching the success end of ajax but the method in my aspx.cs code behind doesn't get called and I have error.

Operation failed! Details :'[object Object]

I'm using a masterpage if it makes a difference.

How to do resolve this ?

Please, can you help me ?

Javascript:

<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"></script>
<script type="text/javascript" src="http://cdn.jsdelivr.net/json2/0.1/json2.js"></script>
<script type="text/javascript">
    $(function () {
        $("[id*=imgfasi]").bind("click", function () {
            var fasi = {};
            fasi.Txseltlc = $("[id*=txseltlc]").val();
            fasi.Txrescldisa = $("[id*=txrescldisa]").val();
            fasi.Ddlauttlc = $("[id*=ddlauttlc]").val();
            $.ajax({
                type: "POST",
                url: "Default.aspx/Savepnfasi",
                data: '{fasi: ' + JSON.stringify(fasi) + '}',
                contentType: "application/json; charset=utf-8",
                dataType: "json",
                success: function (response) {
                    if (response == "1") {
                        alert("Success!");
                    } else {
                        alert("Operation failed! Details: " + response);
                    }
                }
            });
            return false;
        });
    });
</script>

code behind :

public class pnfasiweb
{
    public string Txseltlc { get; set; }
    public string Txrescldisa { get; set; }
    public string Ddlauttlc { get; set; }
}

[WebMethod]
[ScriptMethod]
public static void Savepnfasi(pnfasiweb fasi)
{
    if (!String.IsNullOrEmpty(HttpContext.Current.Request.QueryString["id"]))
    {         
        string ProductID = Mpskmt3.Base64ForUrlDecode(HttpContext.Current.Request.QueryString["id"].ToString());

        string sql = String.Format(@" UPDATE `dotable` ");
        sql += String.Format(" SET ");
        sql += String.Format(" Aut = ?, ");
        sql += String.Format(" Res = ?, ");
        sql += String.Format(" Dur = ?, ");
        sql += String.Format(" Comp = CASE WHEN Comp IS NULL THEN ? ELSE CONCAT(Comp, '; ', ?) END, ");
        sql += String.Format(" doDateHour = CURRENT_TIMESTAMP() ");
        sql += String.Format(" WHERE ID = ?; ");

        using (OdbcConnection cn =
                new OdbcConnection(ConfigurationManager.ConnectionStrings["ConnMySQLlocalhost"].ConnectionString))
        {
            using (OdbcCommand command =
                    new OdbcCommand(sql, cn))
            {
                try
                {
                    command.Connection.Open();                       
                    command.Parameters.AddWithValue("param1", fasi.Ddlauttlc.ToString());
                    command.Parameters.AddWithValue("param2", Convert.ToInt32(fasi.Txrescldisa.ToString()));
                    command.Parameters.AddWithValue("param3", Convert.ToInt32(fasi.Txseltlc.ToString()));
                    command.Parameters.AddWithValue("param4", Mpskmt3.Container.TheObjectPropertyName);
                    command.Parameters.AddWithValue("param5", Mpskmt3.Container.TheObjectPropertyName);
                    command.Parameters.AddWithValue("param6", ProductID.ToString());
                    command.ExecuteNonQuery();
                }
                catch (Exception ex)
                {
                    throw ex;
                }
                finally
                {
                    command.Connection.Close();
                }
            }
        }
    }
    else
    {
       //Error
    }
}

#Edit01

Solution

Try this :

var qString = "?" + window.location.href.split("?")[1];
var fasi = {};

...

url: "Default.aspx/Savepnfasi" + qString,
data: '{fasi: ' + JSON.stringify(fasi) + '}',