string value is Empty when using FromBody in asp.net web api

Question

I am using asp.net core web api. below is my simple post function which is having a single string parameter. The problem is when I use [FromBody] the string stays null. I am using PostMan to test my service. I want raw data to pass from client to my controller. In Postman I am selecting body type RAW and I set the header Content-Type text/plain. The Raw Body contains Just "Hello World" string.

[HttpPost]
        [Route("hosted-services/tokenize-card")]
        public IActionResult Test([FromRoute]decimal businessKey,[FromBody] string body)
        {
            var data = businessKey;
            return new JsonResult("Hello World");
        }

Answer 1

Like the doc says :

When a parameter has [FromBody], Web API uses the Content-Type header to select a formatter.

Only XML and JSON content-types are supported by default. So you need to use application/xml, application/json or register a custom IInputFormatter.

Next, you need to send a content that match the selected content-type. For json, if the parameter is int send a number. If it's a class, send a json object. If it's a string, send a json string. Etc.

int => 14
string => "azerty"
class => { "propName" : "value" }
Array => []
... => ...

In your case you should send application/json content-type and as content :

"Hello string"

And not just

Hello string

Aspnet core json input formatter implementation

Aspnet core xml input formatter implementation

Example: Creating a CSV Media Formatter

Answer 2

I did make it work by passing as row data in PostMan. Do not forget to add "=" sign as prefix in to the values.

 public string Post([FromBody]string value)
 {
     return value;
 }