WebApi POST method with string parameter is always null

Question

I have a POST method in my WebApi that takes json string as parameter.

[HttpPost]  
public HttpResponseMessage GetOrderDataBySessionId([FromBody] string json)

I tried hitting it using RestClient with URL: localhost:56934/api/Home/GetOrderDataBySessionId

and specifying following json string in the Body:

{
  "ListSessionId": [
    "180416073256DGQR10",
    "180416091511DGQR10"
  ]
}

setting the body/content type as application/json. But when it hits my method, the json string parameter is always null.

Is it because I need to use a complex type in parameter?

Can we never have input in string?

If you expect a string, format it as one in the body. Now you are sending a json object, not a string. — Marcus Höglund
– Marcus Höglund, Commented Apr 25, 2018 at 7:26
That is not a string you are sending it's an object, use this for a string "{ \"ListSessionId\": [ \"180416073256DGQR10\", \"180416091511DGQR10\" ] }" — Adeoluwa Simeon
– Adeoluwa Simeon, Commented Apr 25, 2018 at 7:26
@AdeoluwaSimeon Now I know what I was doing wrong.Thanks, Works now :) — Huma Ali
– Huma Ali, Commented Apr 25, 2018 at 7:30

CodeNotFound · Accepted Answer · 2018-04-25 07:27:59Z

2

By sending this content:

{
  "ListSessionId": [
    "180416073256DGQR10",
    "180416091511DGQR10"
  ]
}

You're sending a JSON represented with a proprerty ListSessionId typed as an array of string so your Web API action should be:

public HttpResponseMessage GetOrderDataBySessionId([FromBody] List<string> listSessionId)

Just change the string json to List<string> listSessionId.

answered Apr 25, 2018 at 7:27

CodeNotFound

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Comments

janw · Accepted Answer · 2021-03-19 21:32:44Z

0

I have resolved this problem.

Code in client:

$.ajax({
            url: "/api",
            type: "post",
            data: "p1=1&p2=2"
        });

code in server:

[HttpPost]
public string Post([FromForm] string p1, [FromForm] string p2)
{
    return p1+p2;
}

There are three key points:

The parameter name must be the same both in client and server.
In the client, there must be [FromForm] instead of [FromBody] in front of the parameter.
You can add multiple parameters even, but the parameter names must correspond.

janw

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answered Mar 19, 2021 at 9:57

Winter's Love

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