Issue receiveing POST request with Content-Type text/xml

Question

I'm kinda new to building web applications. I used the template for a ASP.NET Core Web App (Modell-View-Controller) to create a Web Api for REST POST requests.
It was chosen becuase I want to run it on a respberry pi 4 in the end and was able to select the target system when publishing in the Developer PowerShell in VS19.

I currently have a working POST function for request with the Content-Type application/xml. I have to adjust the server POST function because the request is not changeable.

I used an additional service to be able to work with xmls:

services.AddMvc(config =>
                {
                    config.InputFormatters.Insert(0, new XDocumentInputFormatter());
                }).SetCompatibilityVersion(CompatibilityVersion.Latest).AddXmlSerializerFormatters();

The used POST method:

[HttpPost]
        [Consumes("application/xml")]
        public void PostApplXML([FromBody] XDocument value)
        {
        }

I did send my request with Fiddler and received all the data I needed. I also checked it in VS and analyzed the received data.

I have an issue regarding a second POST function for Content-Type text/xml;charset=utf-8. I tried various input parameters to be able to receive the data but was not able to see them in my function.

These are the different ways I have already tried with the responses from Fiddler:

[HttpPost]
       [Consumes("text/xml")]
        public void PostTextXML(HttpRequestMessage request)
        {
          //Fiddler: HTTP/1.1 415 Unsupported Media Type
        }

[HttpPost]
        [Consumes("text/xml")]
        public void PostTextXML([FromBody] HttpRequestMessage request)
        {
            //Fiddler: HTTP/1.1 415 Unsupported Media Type
        }

[HttpPost]
        [Consumes("text/xml")]
        public void PostTextXML(string request)
        {
            //Fiddler: Status OK, request = NULL
        }

[HttpPost]
        [Consumes("text/xml")]
        public void PostTextXML([FromBody] string request)
        {
            //Fiddler: HTTP/1.1 500 Internal Server Error
        }

Edit:
I forgot to mention that I also added an InputFormatter especially for the xml data in the Startup.cs:

public class XDocumentInputFormatter : InputFormatter, IInputFormatter, IApiRequestFormatMetadataProvider
    {
        public XDocumentInputFormatter()
        {
            SupportedMediaTypes.Add("application/xml");
        }

        protected override bool CanReadType(Type type)
        {
            if (type.IsAssignableFrom(typeof(XDocument))) return true;
            return base.CanReadType(type);
        }

        public override async Task<InputFormatterResult> ReadRequestBodyAsync(InputFormatterContext context)
        {
            var xmlDoc = await XDocument.LoadAsync(context.HttpContext.Request.Body, LoadOptions.None, CancellationToken.None);

            return InputFormatterResult.Success(xmlDoc);
        }
    }

Answer 1

Does it mean that I have to create a class with the exact XML structure (or only the values I require from that XML?)

Yes. When you add an input parameter in the action method the model binder tries to match the input parameter to the [FromBody] stream. This is a fundamental concept in Web API.

Try removing the input parameter and read the XML body into a string. From there you can do whatever you need with the XML string.

[HttpPost]
[Produces("text/xml")]
[Consumes("text/xml")]
public async Task<string> PostAsync()
{
    string xml;
    using (System.IO.StreamReader reader = new System.IO.StreamReader(Request.Body, Encoding.UTF8))
    {
        xml =  await reader.ReadToEndAsync();
    }

    return xml;
}

Answer 2

You're struggling with data binding. Web API comes with databinding which coverts the incoming data stream to a string type. This is integrated into the framework.

First, configure the XML formatter in startup.

services.AddControllers().AddXmlSerializerFormatters();

The data model that will be populated by the XML stream

    public class DataModel
    {
        public int id { get; set; }
        public string value { get; set; }
    }

The action to accept and return XML.

[HttpPost]
[Produces("text/xml")]
public DataModel Post([FromBody] DataModel value)
{
    value.value = $"From Post {value.value}";
    return value;
}

The raw xml data sent to the action.

<DataModel>
    <id>1</id>
    <value>Hello World</value>
</DataModel>