Posting to a WCF Data Service 5 - json

Question

I am trying to POST to a EntityFramework backed WCF Data Service but I am getting:
415 Unsupported Media Type
I followed this guide to put the headers into my jQuery POST http://blogs.msdn.com/b/astoriateam/archive/2012/04/11/what-happened-to-application-json-in-wcf-ds-5-0.aspx
These are my headers:
POST /webservices/service/service.svc/Activities HTTP/1.1
Host: www.url.com
Connection: keep-alive
Content-Length: 138
Origin: http://www.url.com
X-Requested-With: XMLHttpRequest
MaxDataServiceVersion: 3.0
User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/536.5 (KHTML, like Gecko) Chrome/19.0.1084.56 Safari/536.5
Content-Type: application/json; charset=UTF-8
Accept: application/json;odata=verbose
Referer: http://www.url.com/sites/site/
Accept-Encoding: gzip,deflate,sdch
Accept-Language: en-US,en;q=0.8,en-GB;q=0.6
Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.3
This site helped with using EntityFramework with WCF Data Services - http://blogs.msdn.com/b/writingdata_services/archive/2011/06/15/entity-framework-4-1-code-first-and-wcf-data-services.aspx
function AddActivity() {
var activity = {
activity:
{
"Title": "Test From Code",
"Detail": "Code Example",
"Started": "2012-06-21T09:00:00",
"UserId": 17
}
};
var url = 'http://www.url.com/webservices/service/service.svc/Activities';
$.ajax({
type: "POST",
url: url,
data: activity,
dataType: "json",
contentType: "application/json; charset=utf-8",
beforeSend: function (xhr) {
xhr.setRequestHeader("Accept", "application/json;odata=verbose");
xhr.setRequestHeader("MaxDataServiceVersion", "3.0");
},
success: function (data) {
alert('Success');
},
error: function (err) {
alert('Fail\n' + err.statusText);
}
});
}
I can read data JSON data OK

Answer 1

WCF Data Services 5.0 does not support application/json content type for request (or response) payloads if the payload has version V3 (DataServiceVersion). In the above case you didn't specify the DataServiceVersion (which you always should by the way). The server in such case has to infer the version somehow, the WCF Data Service server will assume the maximum version it and the client understands. Since the server itself understands V3 and you specified MaxDataServiceVersion: 3.0 which means the client also understands V3 it assumes the payload is a V3 payload.
V3 payloads currently don't support application/json, they only support application/json;odata=verbose.
See this blog post for more explanation: http://blogs.msdn.com/b/astoriateam/archive/2012/04/11/what-happened-to-application-json-in-wcf-ds-5-0.aspx. It talks about GET but the same things applies to POST and such as well.
So to fix your problem, modify your client to either send DataServiceVersion: 2.0 (or 1.0) if that would be correct, or even better modify it to send Content-Type: application/json;odata=verbose (which will work no matter the payload version).

Answer 2

Just did this with minimal hacking, using WCF without any WCF Data Services components.
Posting a minimal type back as JSON will automap the values, for example, this JSON
{
"name": "1234567890",
"amount": "2500.00"
}
can post back to this service
[WebInvoke(Method = "POST", ResponseFormat = WebMessageFormat.Json, BodyStyle = WebMessageBodyStyle.Bare, RequestFormat = WebMessageFormat.Json)]
public string MethodName(Message message)
where Message is C# class:
public class Message
{
public string name { get; set; }
public string amount { get; set; }
}
Pretty simple. Then, if you want to process it as an OData request, you have more complex JSON being posted, example (ODataV2):
{
"d": [
{
"__metadata": {
"id": "http://host:54470/ods.svc/MethodName('1234567890')",
"uri": "http://host:54470/ods.svc/MethodName('1234567890')",
"type": "SomeCompany.Helper.Services.RequestMessage.Message"
},
"name": "1234567890",
"amount": "2500.00",
}
]
}
If you create corresponding C# classes, this OData will map to those classes. These classes work with the OData.
public class Message
{
public ODataResult[] d;
}
public class ODataResult
{
public ODataMetaData __metadata;
public string name { get; set; }
public string amount { get; set; }
}
public class ODataMetaData
{
public string id;
public string uri;
public string type;
}
The json posted OData will map to this Message class. This gives you a way to 'shape' the incoming message as needed, which might be required in some cases.
Not saying this is better than using WCF Data Services, just saying it will work.