Asp.net core: action with raw string parameter

Question

I'm trying to write an action with a raw string parameter.

This string will be parsed dynamically as a json, so the keys in the json are not know at compile time.

I declared the method in this way:

[HttpPost("MyAction")]
public async Task<ActionResult<long>> MyAction([FromBody] string command)
{
    var cmd = MyCqrsCommand(command);
    return await Mediator.Send(cmd);
}

I call the method with swagger that shows a parameter as application/json

The result is this

{
  "type": "https://tools.ietf.org/html/rfc7231#section-6.5.1",
  "title": "One or more validation errors occurred.",
  "status": 400,
  "traceId": "|4e0e9c40-4036f8a9873ecac8.",
  "errors": {
    "$": [
      "The JSON value could not be converted to System.String. Path: $ | LineNumber: 0 | BytePositionInLine: 1."
    ]
  }
}

I found two different solutions:

[HttpPost("MyAction")]
public async Task<ActionResult<long>> MyAction([FromBody] object command)
{ ... }
    
[HttpPost("MyAction")]
public async Task<ActionResult<long>> MyAction(string command)
{ ... }

Using object is not elegant but it works. Using "string" in uri has some limitations, so I prefer the previous.

Which one is the best solution? And is there a way to insert the string in body declared as string and not object?

qqtf · Accepted Answer · 2024-06-15 10:38:11Z

1

Use JsonObject as an input parameter instead of string and object.

update 2024/06/12

from the same micrososft link:

The System.Json namespace was designed for Silverlight, which is no longer supported. For processing JSON, we recommend using APIs in the System.Text.Json namespace instead.

this answer no longer seems to be valid

edited Jun 15, 2024 at 10:38

qqtf

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answered Sep 18, 2020 at 8:41

Maxim Tkachenko

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2 Comments

Tonyc Over a year ago

OK, but this seems to require a specific json structure (from swagger): { "count": 0, "item": [ null ], "jsonType": 0, "keys": [ "string" ], "values": [ [ null ] ] }; I prefer to have a free json to parse. Is it possible?

qqtf Over a year ago

from the learn.microsoft-link you mention: The System.Json namespace was designed for Silverlight, which is no longer supported. For processing JSON, we recommend using APIs in the System.Text.Json namespace instead.

Michael Wang · Accepted Answer · 2020-09-25 07:17:52Z

Which one is the best solution?

I perfer to use object parameter solution.

[HttpPost("MyAction")]
public async Task<ActionResult<long>> MyAction([FromBody] object command)
{ ... }

From the screenshot of your request we can see, you sent a JSON object { "key": "value" } to your MyAction method. So you shouldn't declared your parameter as string.

And is there a way to insert the string in body declared as string and not object?

If you expect to use "string" as input parameter, just send the content of value.

    [HttpPost("/MyAction")]
    public async Task<ActionResult<long>> MyAction([FromBody] string command)

You sent "value" which is not a valid json that usually is sent. Try to send the body with a valid json and you will see that your solution doesn't work

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