Question

I’m messing about with my first WCF service and I am having problems passing parameters.

My jQuery ajax call looks like this…

$.ajax({
    type    : 'POST',
    async   : true,
    url     : 'Service2.svc/GetStats',
    contentType: 'application/json; charset=utf-8',
    data    : '{ i : 12 }',
    dataType: 'json',
    success : function(result) {
        //success routine...
    }
});

add my service code is like…

<OperationContract()> _
<WebInvoke(ResponseFormat:=WebMessageFormat.Json, RequestFormat:=WebMessageFormat.Json)> _
Public Function GetStats(ByVal i As Integer) As Results
    Dim returnValue As New Results
    returnValue.iValue1 = 10
    returnValue.iValue2 = 20
    returnValue.sMessage = "You executed " + "sdfsd"
    Return returnValue
End Function

Results class is a really simple holder class, two Integers and a String.

This service works fine if I remove the parameters from GetStats and remove the corresponding data property from my $.ajax object – I can access the three returned values on the client.

When the parameter i is included I get an Internal Server Error status:500.

I’m guessing I’m missing an attribute or something from my service Function?

Answer 1

Thanks for the responses.

I spent a while wrestling with this one and all I needed to do was…

        data    : '{"i" : 12}' ,  //Object name i in double-quotes

So contrary to some of the other suggestions i do want to pass the JSON as a string. (I suppose one should really use a library such as Crockford’s JSON for this)

However I could only discover this after finding what the actual error was. I did this by throwing this snippet into my web.config file…

<system.diagnostics>
  <sources>
    <source name="System.ServiceModel" switchValue="Warning, ActivityTracing"
      propagateActivity="true">
      <listeners>
        <add type="System.Diagnostics.DefaultTraceListener" name="Default">
          <filter type="" />
        </add>
        <add name="ServiceModelTraceListener">
          <filter type="" />
        </add>
      </listeners>
    </source>
  </sources>
  <sharedListeners>
    <add initializeData="app_tracelog.svclog"
      type="System.Diagnostics.XmlWriterTraceListener, System, Version=2.0.0.0, 
        Culture=neutral, PublicKeyToken=b77a5c561934e089"
        name="ServiceModelTraceListener" traceOutputOptions="Timestamp">
      <filter type="" />
    </add>
  </sharedListeners>
</system.diagnostics>

I got this from mkdot.net and it should really be generated using SvcConfigEditor.exe – which I couldn’t find on my locked down machine. But just pasting that in seemed to work – and gave me a log file in my development folder – this actually told me the nature of the error.