JSON deserialization error in WebApi with array

Question

I'm posting the following JSON payload from a JavaScript Angular app to a webapi service:

{Notes: "test", Ids: [606, 603]}

this.http.post(url, {"Notes": "test", "Ids": [606,603]}, options)

I'm attempting to deserialize this into a .net Dictionary like:

[HttpPost]
public IHttpActionResult Test(Dictionary<string,string> formData)
{
}

(I've tried to add the [FromBody] decorator too).

If I don't include the array, this works fine. But with the array, I get a couple of parse error:

Unexpected character encountered while parsing value: [. Path 'Ids', line 1, position 23. Invalid JavaScript property identifier character: ]. Path 'Ids', line 1, position 30.

Not all values in the payload are string. use Dictionary<string,object> — Nkosi
– Nkosi, Commented Jul 26, 2017 at 15:19

J.N. · Accepted Answer · 2017-07-26 15:19:58Z

1

The "JSON" you're posting is not valid JSON - you can use a tool like JSONLint to validate your JSON.

The correct JSON syntax for your data is:

{
    "Notes": "test",
    "Ids": [606, 603]
}

Also - the method takes a Dictionary<string,string> object. Your array is not a string, and the controller will therefore fail while trying to deserialize the array into a string.

My suggestion is to create a model, which the controller method should receive. Like this:

[HttpPost]
public IHttpActionResult Test(YourModel data)
{
}

class YourModel 
{       
    public string Notes {get;set;}
    public int[] Ids {get;set;}
}

Using this code, the controller will deserialize your JSON (when you have corrected the JSON syntax problems) into an instance of YourModel.

edited Jul 26, 2017 at 15:19

answered Jul 26, 2017 at 14:52

J.N.

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5 Comments

Michael Witt Over a year ago

Since my javascript looks like: this.http.post(url, {"Notes": notes, "Ids": idList}, options) - Any idea how to get it to format correctly? Also, the parse error notes that it found an error parsing "[". I'm going to add the javascript to the OP.

Michael Witt Over a year ago

One other thought, if I send just: {Notes: "test"} in the payload (javascript being {"Notes": "test"}), it is accepted. So I think it is a problem with the array.

J.N. Over a year ago

@MikeWitt - You're correct, the array is also a problem. I've updated my answer.

Michael Witt Over a year ago

@.J.N. - Thanks, couldn't see the forest for the trees I guess :). Using Dictionary<string,object> worked.

J.N. Over a year ago

@MikeWitt. You're welcome - using a dedicated model which the controller can be used to deserialize to will, in the long run, make it much easier for you to work with the data IMO. But great that you got it working!

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