Sending empty array to webapi

Question

I want to POST an empty javascript array [] to webAPI and have it create an empty list of integers. I also want it so if I post javascript null to webAPI that it assigns null to the list of integers.

JS:

var intArray = [];
$.ajax({
    type: 'POST',
    url: '/api/ListOfInts',
    data: {'' : intArray},
    dataType: 'json'
});

c# webapi

[HttpPost]
public void ListOfInts([FromBody]List<int> input)

Problem 1) Jquery refuses to send data {'' : []} as the post payload. As soon as I add something in the array it works such as {'' : [1,2,3]}

Problem 2) Passing empty js array to controller gives null Based on what i read even if I do get it to post an empty array, it will initialize the list as null. Discussed solutions have it so that the list is always initializes as empty but I don't want that. I want it to be null in some case (when null/undefined is sent to it) and when [] is sent it should initialize as empty.

Edit: See https://www.asp.net/web-api/overview/advanced/sending-html-form-data-part-1 about why I am using {'' : []}

Yes, it doesnt work at all. WebAPI doesnt know how to handle it — LearningJrDev, Jun 09 '16 at 14:58
In WebApi, differentiating between null and empty in a request can be difficult. If you are using those to somehow set some sort of "state" in your application, I would rethink how you are doing it. Possibly sending some sort of flag or something that will properly initialize your list on the server. — jensendp, Jun 17 '16 at 14:56

score 24 · Answer 1 · answered Jun 17 '16 at 20:36

Use JSON.stringify(intArray) and contentType: 'application/json' works for me:

$.ajax({
     url: "/api/values",
     method: "POST",
     contentType: 'application/json',
     data: JSON.stringify([])
});

$.ajax({
     url: "/api/values",
     method: "POST",
     contentType: 'application/json',
     data: null
});

$.ajax({
      url: "/api/values",
      method: "POST",
      contentType: 'application/json',
      data: JSON.stringify([1, 2, 3])
});

score 1 · Answer 2 · answered Jun 07 '16 at 20:34

1

data: {'' : intArray},

a blank key name is not allowed in JSON.

Just send the array itself.

data: intArray,

answered Jun 07 '16 at 20:34

Jeremy J Starcher

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This is required by webAPI when sending a valuetype – LearningJrDev Jun 07 '16 at 20:36
According to [this question and answer](http://stackoverflow.com/q/33254385/548304), empty keys are allowed. – zastrowm Jun 17 '16 at 22:01

score 1 · Answer 3 · edited May 23 '17 at 11:45

1

1. Use JSON.stringify() to convert javascript object to JSON string.

2. Use contentType: 'application/json' as it is correct MIME media type for JSON. What is the correct JSON content type?

3 dataType is not necessary

data: JSON.stringify(intArray), contentType: 'application/json'

edited May 23 '17 at 11:45

Community

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1

answered Jun 20 '16 at 12:47

Alexandr

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Sending empty array to webapi

3 Answers3