Incoking a WebGet throws an exception

Question

I have a custom web method to return a distinct list of string of any property of any entity set:

[WebGet]
public ObjectQuery<string> GetList(string entitySet, string propertyName)
{
  return this.CurrentDataSource.CreateQuery<string>(string.Format("SELECT VALUE E.{1} FROM MyEntities.{0} AS E", entitySet, propertyName)).Distinct();
}

I have tried to invoke it using the CreateQuery method:

MyEntities.CreateQuery<string>("/GetList").AddQueryOption("entitySet","'Test'").AddQueryOption("propertyName","'Test'").BeginExecute(....);

But the generated uri contains the round brackets which are wrong and generated an error on the server side:

http://localhost:1234/MyEntitiesService.svc/GetList()?entitySet='Test',propertyName='Test'

So I have generated the uri and used the DataServiceContext.BeginExecute method:

MyContext.BeginExecute<string>(new Uri(string.Format("/GetList?entitySet='{0}'&propertyName='{1}'", "Test", "Test"), UriKind.Relative), ar =>
{
  this.TestList = MyContext.EndExecute<string>(ar).ToList();
},null);

But still I get an exception when I invoke the EndExecute method:

Error processing response stream. The XML element contains mixed content.
   at System.Data.Services.Client.MaterializeAtom.ReadElementString(Boolean checkNullAttribute)
   at System.Data.Services.Client.MaterializeAtom.ReadNext(ClientType currentType, Type expectedType, AtomParseState atom, EntityStates& entityState, Object& currentValue)
   at System.Data.Services.Client.MaterializeAtom.MoveNext()
   at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
   at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)

How do I invoke a WebGet method?

Answer 1

Hi Aquilax,

Unfortunately our client today does not support primitive type materialization - it can only materialize Atom payload.

However, you can make a custom HttpWebRequest to the service end point and parse the primitive type payload yourself. The format of the payload is:

	<ServiceOpName xmlns="http://schemas.microsoft.com/ado/2007/08/dataservices">
	<element xml:space="preserve">Value   </element> ... </ServiceOpName> Regards, PQ

---

Peter Q. http://blogs.msdn.com/peter_qian

Answer 2

Hi Peter

Thanks for the answer, it's what I have done. I though there was a better way but as I see there isn't. Here some code if someone is looking for a solution to the same problem:

WebClient wc = new WebClient();

wc.DownloadStringAsync(new Uri(string.Format("http://localhost:4443/WebDataService.svc/GetList?entitySet='{0}'&propertyName='{1}'", entitySet, propertyName)));
wc.DownloadStringCompleted += (s, e) =>
{
    XDocument xdoc = XDocument.Parse(e.Result);
    List<string> list = xdoc.Root.Descendants(((XNamespace)@"http://schemas.microsoft.com/ado/2007/08/dataservices") + "element").Select(xe => xe.Value).ToList();
};