AspNet WebApi POST parameter is null when sending XML

Question

I have a web api service originally using beta bits which I've rebuilt using the release candidate bits and I'm now having this problem.

I have a POST action that takes a complex option as the only parameter. When I send the request with the body in json format the object is deserialised as expected, but if I send XML instead the parameter is null.

In the beta I worked around this by disabling model binding as described in Carlos Figueira's blog post Disabling model binding on ASP.NET Web APIs Beta

In the RC however they have removed the IRequestContentReadPolicy that this method was implementing.

My action:

public List<Models.Payload> Post([FromBody]Models.AimiRequest requestValues)
{
  try
  {
    if (requestValues == null)
    {
      var errorResponse = new HttpResponseMessage();
      errorResponse.StatusCode = HttpStatusCode.NotFound;
      errorResponse.Content = new StringContent("parameter 'request' is null");
      throw new HttpResponseException(errorResponse);
    }
    var metadataParams = new List<KeyValuePair<string, string>>();
    foreach (Models.MetadataQueryParameter param in requestValues.Metadata)
    {
      metadataParams.Add(new KeyValuePair<string, string>(param.Name, param.Value));
    }
    List<Core.Data.Payload> data = _payloadService.FindPayloads(metadataParams, requestValues.ContentType, requestValues.RuleTypes);
    var retVal = AutoMapper.Mapper.Map<List<Core.Data.Payload>, List<Models.Payload>>(data);
    return retVal; // new HttpResponseMessage<List<Models.Payload>>(retVal);
  }
  catch (System.Exception ex)
  {
    _logger.RaiseError(ex);
    throw;
  }
}

My model:

public class AimiRequest
{
  public MetadataQueryParameter[] Metadata { get; set; }
  public string ContentType { get; set; }
  public string RuleTypes { get; set; }
}

public class MetadataQueryParameter
{
  public string Name { get; set; }
  public string Value { get; set; }
}

I'm testing using Fiddler to send requests to the service.

This works and returns me the expected results.

POST http://localhost:51657/api/search HTTP/1.1
User-Agent: Fiddler
Content-Type: application/json; charset=utf-8
Accept: application/json
Host: localhost:51657
Content-Length: 219

{
  "ContentType":null,
  "RuleTypes":null,
  "Metadata":[
    {
    "Name":"ClientName",
    "Value":"Client One"
    },
    {
    "Name":"ClientName",
    "Value":"Client Two"
    }
  ]
}

This fails because the requestValues parameter is null

POST http://localhost:51657/api/search HTTP/1.1
User-Agent: Fiddler
Content-Type: application/xml; charset=utf-8
Accept: application/xml
Host: localhost:51657
Content-Length: 213

<AimiRequest>
  <ContentType />
  <RuleTypes />
  <Metadata>
    <MetadataQueryParameter>
      <Name>ClientName</Name>
      <Value>Client One</Value>
    </MetadataQueryParameter>
    <MetadataQueryParameter>
      <Name>ClientName</Name>
      <Value>Client Two</Value>
    </MetadataQueryParameter>
  </Metadata>
</AimiRequest>

See details in this [question][1]... [1]: stackoverflow.com/questions/14068288/… — barrypicker
– barrypicker, Commented Jul 25, 2013 at 21:21

matthughes404 · Accepted Answer · 2012-06-27 17:38:36Z

26

By adding the following lines to the ApplicationStart() method in your Global.asax.cs, your original XML request should work:

var xml = GlobalConfiguration.Configuration.Formatters.XmlFormatter;
xml.UseXmlSerializer = true;

By default, the Web API uses the DataContractSerializer class, which requires extra information in the XML request.

The XmlSerializer seems to work more smoothly for me, since I don't have to add the model's namepsace to each XML request.

Once again, i found my information in Mike Wasson's article: http://www.asp.net/web-api/overview/formats-and-model-binding/json-and-xml-serialization#xml_media_type_formatter

answered Jun 27, 2012 at 17:38

matthughes404

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2 Comments

Jonas Wik Over a year ago

this was the solution I was looking for. I had the same problem where json would work fine, but object would always be null when using xml

gkonuralp Over a year ago

not working for me. now the app is returning "The request entity's media type 'application/xml' is not supported for this resource.".

matthughes404 · Accepted Answer · 2012-06-27 17:39:22Z

I was having the same problem as you, and found the solution by serializing the object using the XmlMediaTypeFormatter as described here: http://www.asp.net/web-api/overview/formats-and-model-binding/json-and-xml-serialization#testing_object_serialization. I used the code in the "Testing Object Serialization" section at the bottom of the article, and replaced his Person object with my model.

When I serialized my object, I noticed that the following attributes were added to the root node:

xmlns:i="http://www.w3.org/2001/XMLSchema-instance" 
xmlns="http://schemas.datacontract.org/2004/07/NAMESPACE.OF.YOUR.MODEL"

If you add these attributes to your xml like so, your controller should correctly serialize the requestValues object:

<AimiRequest xmlns:i="http://www.w3.org/2001/XMLSchema-instance" 
  xmlns="http://schemas.datacontract.org/2004/07/NAMESPACE.OF.YOUR.MODEL">
  <ContentType />
  <RuleTypes />
  <Metadata>
    <MetadataQueryParameter>
      <Name>ClientName</Name>
      <Value>Client One</Value>
    </MetadataQueryParameter>
    <MetadataQueryParameter>
      <Name>ClientName</Name>
      <Value>Client Two</Value>
    </MetadataQueryParameter>
  </Metadata>
</AimiRequest>

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