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
– Panagiotis Kanavos, Commented Nov 1, 2019 at 14:03
FromForm that - forms don't use JSON - JSON was invented at least a decade later. Use a FormUrlEncodedContent instace with PostAsync. All it needs as input is anything that implements IEnumerable<System.Collections.Generic.KeyValuePair<string,string>> like a Dictionary<string,string> — Panagiotis Kanavos
– Panagiotis Kanavos, Commented Nov 1, 2019 at 14:06
On the other hand, if that PostData method isn't used with forms, you could just remove [FromForm] — Panagiotis Kanavos
– Panagiotis Kanavos, Commented Nov 1, 2019 at 14:08

TrevorBrooks · Accepted Answer · 2019-11-01 14:09:12Z

2

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

answered Nov 1, 2019 at 14:09

TrevorBrooks

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7 Comments

Now the PostData method does not fire at all.

Have you changed the ContentType to application/json?

You may also want to remove the RequestFormLimits attribute from the method as well.

Ok will do but I put that there because I will be passing quite large data.

Do I set the content type on the DefaultRequestHeaders?

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