Call WebApi Endpoint Passing in Object

Question

I have the following endpoint

[HttpPost]
[DisableRequestSizeLimit]
[RequestFormLimits(KeyLengthLimit = int.MaxValue)]
public IActionResult PostData([FromForm]Data data)

The Data class looks like this

public class Data
{
    public string A { get; set; }
    public string B { get; set; }
}

I am calling this endpoint in this way

var url = ...;

var client = new HttpClient();
var data = new
{
    a = "Foo",
    b = "Bar"
};
var result = await client.PostAsJsonAsync(url, data);

But the data parameter in the PostData method always is null. Any ideas what I am doing wrong?

That's not an `out` parameter so what does `comes back` mean? `result` won't be null either, it will always contain the response — Panagiotis Kanavos, Nov 01 '19 at 14:03
`FromForm` that - forms don't use JSON - JSON was invented at least a decade later. Use a [FormUrlEncodedContent](https://learn.microsoft.com/en-us/dotnet/api/system.net.http.formurlencodedcontent?view=netcore-3.0) instace with `PostAsync`. All it needs as input is anything that implements `IEnumerable>` like a `Dictionary` — Panagiotis Kanavos, Nov 01 '19 at 14:06
On the other hand, if that `PostData` method isn't used with forms, you could just remove `[FromForm]` — Panagiotis Kanavos, Nov 01 '19 at 14:08

score 2 · Accepted Answer · answered Nov 01 '19 at 14:09

2

If your content type is application/json use [FromBody] instead of [FromForm].

answered Nov 01 '19 at 14:09

TrevorBrooks

Now the PostData method does not fire at all. – Sachin Kainth Nov 01 '19 at 14:24
Have you changed the ContentType to application/json? – TrevorBrooks Nov 01 '19 at 14:26
You may also want to remove the RequestFormLimits attribute from the method as well. – TrevorBrooks Nov 01 '19 at 14:28
Ok will do but I put that there because I will be passing quite large data. – Sachin Kainth Nov 01 '19 at 14:31
Do I set the content type on the DefaultRequestHeaders? – Sachin Kainth Nov 01 '19 at 14:32
@SachinKainth `PostAsJsonAsync` already sets the content type as `application/json` – Nkosi Nov 01 '19 at 14:33
https://stackoverflow.com/questions/10679214/how-do-you-set-the-content-type-header-for-an-httpclient-request – TrevorBrooks Nov 01 '19 at 14:44

1 Answers1