Ajax passing null value to controller

问题

I have a dropdown that has a list of ID's in it. The customer will select one and it will reflect a price total on the page. Im creating an ajax call that will update the total when a different ID is pulled from the Dropdown.

$("#BrandId").on('focus', function () {
    // Store the current value on focus and on change
    previous = this.value;
}).change(function () {
    alert("Previous: " +previous);
    sel = this.value;
    alert("Selected: " +sel);
    $.ajax({
        cache: false,
        type: "get",
        contentType: "application/json; charset=utf-8",
        url: '@Url.Action("GetBrandCost", "Shocks")',
        data: JSON.stringify({ idp: previous, id: sel }),
        dataType: "json",
        aysnc: false,
        success: function (data1) {
            alert(data1);
                //ShockTotal = $("#ShockTotal").html();
                //ShockTotal = ShockTotal / 1;
                ////ShockTotal = ShockTotal - data1;
                //$("#ShockTotal").html(data1);

        }
    });
});

The alerts are working perfectly but the ajax isnt passing those ID's into the controller, the controller is just receiving nulls.

 public decimal GetBrandCost(string idp, string id)
    {
        decimal costp = 0;
        decimal cost = 0;
        if (id == "" || id == null || idp == "" || idp == null)
        {
            return 0;
        }
        ShockBrand brandp = db.ShockBrands.Find(idp);
        costp = brandp.Cost;
        ShockBrand brand = db.ShockBrands.Find(id);
        cost = brand.Cost;
        cost = cost - costp;
        return cost;
    }

Since they are null I am hitting my if statement and just returning zero inside the success. Most of the things I read were to add the content type but that didnt seem to help in my case, Im sure it is something little.

回答1:

From browser console, this

$.ajax({
        cache: false,
        type: "get",
        contentType: "application/json; charset=utf-8",
        url: 'http://google.com',
        data: JSON.stringify({ idp: 1, id: 2 }),
        dataType: "json",
        aysnc: false,
        success: function (data1) {
           console.log(data1)

        }
    });

returns request to http://google.com/?{%22idp%22:1,%22id%22:2}&_=1440696352799, which is incorrect

and without stringify

$.ajax({
        cache: false,
        type: "get",
        contentType: "application/json; charset=utf-8",
        url: 'http://google.com',
        data: { idp: 1, id: 2 },
        dataType: "json",
        aysnc: false,
        success: function (data1) {
           console.log(data1)

        }
    });

returns http://google.com/?idp=1&id=2&_=1440696381239 (see Network tab)

So don't use JSON.stringify

Why it's gonna work - your asp.net controller action receives simple typed parameters (string, numbers, etc) and jquery is fairly enought smart to determine what are going to send, if it was object inside object it will send it as POST data for POST, and string represenation of object for GET (you have GET request, but for purpose of knowledge, just stick with 2 types of data that can be send, params & data) So when jquery configures url, asp.net understands conventions, and matches request to approciated action

But Don't believe me, check it yourself

chrome dev console is your friend