how to post plain text to ASP.NET Web API endpoint?

Question

I have an ASP.NET Web API endpoint with controller action defined as follows :

[HttpPost]
public HttpResponseMessage Post([FromBody] object text)

If my post request body contains plain text ( i.e. should not be interpreted as json, xml, or any other special format ), then I thought I could just include following header to my request :

Content-Type: text/plain

However, I receive error :

No MediaTypeFormatter is available to read an object of type 'Object' from content with media type 'text/plain'.

If I change my controller action method signature to :

[HttpPost]
public HttpResponseMessage Post([FromBody] string text)

I get a slightly different error message :

No MediaTypeFormatter is available to read an object of type 'String' from content with media type 'text/plain'.

Answer 1

Actually it's a shame that web API doesn't have a MediaTypeFormatter for plain text. Here is the one I implemented. It can also be used to Post content.

public class TextMediaTypeFormatter : MediaTypeFormatter
{
    public TextMediaTypeFormatter()
    {
        SupportedMediaTypes.Add(new MediaTypeHeaderValue("text/plain"));
    }

    public override Task<object> ReadFromStreamAsync(Type type, Stream readStream, HttpContent content, IFormatterLogger formatterLogger)
    {
        var taskCompletionSource = new TaskCompletionSource<object>();
        try
        {
            var memoryStream = new MemoryStream();
            readStream.CopyTo(memoryStream);
            var s = System.Text.Encoding.UTF8.GetString(memoryStream.ToArray());
            taskCompletionSource.SetResult(s);
        }
        catch (Exception e)
        {
            taskCompletionSource.SetException(e);
        }
        return taskCompletionSource.Task;
    }

    public override Task WriteToStreamAsync(Type type, object value, Stream writeStream, HttpContent content, System.Net.TransportContext transportContext, System.Threading.CancellationToken cancellationToken)
    {
        var buff = System.Text.Encoding.UTF8.GetBytes(value.ToString());
        return writeStream.WriteAsync(buff, 0, buff.Length, cancellationToken);
    }

    public override bool CanReadType(Type type)
    {
        return type == typeof(string);
    }

    public override bool CanWriteType(Type type)
    {
        return type == typeof(string);
    }
}

You need to "register" this formatter in your HttpConfig by something like that:

config.Formatters.Insert(0, new TextMediaTypeFormatter());