Web API [FromBody] 始终 null

Question

Im currently creating a Web API that writes into a table. Im using [FromBody] tag to pass the values for the table.

The problem is that the [FromBody] value is always null. Im using Advanced Rest Client to test my API.

public HttpResponseMessage Post(int id, [FromBody]string value)
{
     //DO Something
}

Answer 1

The problem is in the type conversion. You are sending an array with one value containg a dictionary and trying to recieve a string in the method. ASP.NET can't cast your structure to string and use null as default value.

So, the simple way to test method is to pass a simple string in body. But the right way is to change the type of object passing into action method:

public HttpResponseMessage Post(int id, [FromBody]List<Dictionary<string,string>> value)
{
     //DO Something
}

It's strange to parse JSON manually when the system does it, but then you should pass string to the method. Just wrap your body to "" and you'll get a plain JSON in the method. Also you can read body manually via StreamReader :

public HttpResponseMessage Post(int id)
{
    using (StreamReader reader = new StreamReader(Request.Body, Encoding.UTF8))
    {  
        var plainBody = reader.ReadToEnd();
    }
}

Answer 2

If you don't want the body deserialized, you can just read the string from the Request.Body property.

public Task<HttpResponseMessage> Post(int id)
{
    var reader = new StreamReader(Request.Body);
    var bodyString = await reader.ReadToEndAsync();

    ...
}