jQuery posts null instead of JSON to ASP.NET Web API

Question

I can\'t seem to get this to work... I have some jQuery like this on the client:

$.ajax({
    type: \"POST\",
    url: \"api/report/reportexists/\",
    data         


        

Answer 1

So I found the problem, and the solution. So, first thing first. The contentType cannot be 'application/json', it has to be blank (default to application/x-www-form-urlencoded I believe). Although it seems you have to SEND json, but without a name in the name value pair. Using JSON.stringify also messes this up. So the full working jQuery code is like this:

$.ajax({
    type: "POST",
    url: "api/slideid/reportexists",
    data: { "": reportpath },
    success: function(exists) {
        if (exists) {
            fileExists = true;
        } else {
            fileExists = false;
        }
    }
});

On the Web.API side, you MUST have the [FromBody] attibute on the parameter, but other than this it's pretty standard. The real problem (for me) was the post.

In Fiddler, the request body looked like this "=%5C%5Croot%5Cdata%5Creport.html"

This post really had the answer, and linked to this article which was also very helpful.

Answer 2

If you're using MVC's FromBody attribute, the MVC binder treats this as an optional parameter. This means you need to be explicit about the Parameter names even if you've only got a single FromBody parameter.

You should be able to work with something as simple as this:

Controller:

[HttpPost]
public bool ReportExists( [FromBody]string report )
{
    bool exists = File.Exists(report);
    return exists;
}

Javascript:

$.ajax({
    type: "POST",
    url: "api/report/reportexists/",
    data: { "report":reportpath },
    success: function(exists) {
    ...

You must ensure that your data object in jQuery matches the parameter names of your Controllers exactly.

Answer 3

$.post served the purpose for me. Remove the [FromBody] from webapi and give the url in the url parameter of the $.post in jquery client. It worked!

Answer 4

This worked for me, all other approaches didn't:

function addProduct() {
        var product = { 'Id': 12, 'Name': 'Maya', 'Category': 'newcat', 'Price': 1234 };             
        $.ajax({
            type: "POST",
            url: "../api/products",
            async: true,
            cache: false,
            type: 'POST',
            data: product,
            dataType: "json",
             success: function (result) {

            },
            error: function (jqXHR, exception) {
                alert(exception);
            }
        });
    }

Serverside:

 [HttpPost]
    public Product[] AddNewProduct([FromBody]Product prod)
    {
        new List<Product>(products).Add(prod);
        return products;
    }

Answer 5

jQuery.ajax() by default sets the contentType to be application/x-www-form-urlencoded. You could send the request in application/json instead. Also, you should send your data as a string and it will get model bind to the report parameter for your post method:

$.ajax({
    type: "POST",
    url: "api/report/reportexists/",
    contentType:  "application/json",
    data: JSON.stringify(reportpath),
    success: function(exists) {
        if (exists) {
            fileExists = true;
        } else {
            fileExists = false;
        }
    }
});