CODEWITHSUNDEEP
c#asp.net-web-api2postman
Buda Gavril
Buda Gavril

Reputation: 21627

web api: action parameter is null

I have a simple web api but when I test it with Postman, the method parameter is null. I've looked and over other questions with similar title but I haven't found an answer.

Here is my controller action:

    [HttpPost]
    public Member Create([FromBody] string payload)
    {
        var s = Request.Content.ReadAsStringAsync();

        if (payload == null)
        {
            throw new ArgumentNullException(nameof(payload));
        }

        Console.WriteLine(payload);
        Console.WriteLine(s);

        return null;
    }

And here is my postman configuration: enter image description here

In the headers tab I've added content-type to be application/json.

when I'm debugging this, the payload variable is allways null and the string s contains something like 

Id = 98, Status = RanToCompletion, Method = "{null}", Result = ""

So what am I doing wrong?

Upvotes: 1

Views: 1145

Answers (2)

Roman
Roman

Reputation: 12171

You should wrap your string in model (object): 

class Model
{
    public string payload {get;set;}
}

[HttpPost]
public async Task<Member> Create([FromBody] Model model) // wrap Member in Task and add async keyword
{
    var s = await Request.Content.ReadAsStringAsync(); // add await here

    if (model.payload == null)
    {
        throw new ArgumentNullException(nameof(model.payload));
    }

    Console.WriteLine(model.payload);
    Console.WriteLine(s);

    return null;
}

If you don't want to use model, try to send only plain string, like "some payload", do not wrap it in json.

Upvotes: 0

Vivien Chevallier
Vivien Chevallier

Reputation: 1522

Buda,

HttpContent.ReadAsStringAsync returns a Task<string>, hence the value of the s string.

You have to update your action to make it async:

[HttpPost]
public async Task<Member> Create([FromBody] string payload)
{
    var s = await Request.Content.ReadAsStringAsync();

    if (payload == null)
    {
        throw new ArgumentNullException(nameof(payload));
    }

    Console.WriteLine(payload);
    Console.WriteLine(s);

    return null;
}

Upvotes: 1

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