Windows应用商店应用程序，调用DataServiceQuery.EndExecute（）时WCF数据服务InvalidOperationException？

Question

I lookup relative data find that Windows store app only support async WCF calling to ensure the responsive UI. Here is a relative question.

I achieve my data service and do like that. Here is the code:

MyDataServiceContext ctx = new MyDataServiceContext(uri);

DataServiceQuery<COURSE_OK> query =
        (DataServiceQuery<COURSE_OK>)(from crs in ctx.COURSE_OK
                                      select crs);

TaskFactory<IEnumerable<COURSE_OK>> tf = new TaskFactory<IEnumerable<COURSE_OK>>();
var result = await tf.FromAsync(query.BeginExecute(null, null),
                                ira => query.EndExecute(ira)); // InvalidOperationException

foreach (var a in result)
{
    System.Diagnostics.Debug.WriteLine("{0}", a.TITLE);
}

I succeeded only once, after that it always crash in query.EndExecute(ira) method and said InvalidOperationException was unhandled by user code.

In addition, it works well in Console Application. I guess that the main problem is Windows store app, but how to solve this?

Answer 1

Your function looks quite good. This is what works for me:

var queryTask = Task.Factory.FromAsync<IEnumerable<TResult>>(query.BeginExecute(null, null), (asResult) =>
{
   var result = query.EndExecute(asResult).ToList();
   return result;
});

Maybe you should not initialize your context on every call. Just initialize it once and reuse it every time you need it.