如何在UWP中使用BeginExecute与分页异步使用WCF数据服务

Question

I have a WCF Data Services service and its methods return Queryable lists.

Using a Java library, I could consume it with client-side paging (using top and take ).

Now I intend to consume it with an UWP application.

Unfortunately the following code does not work:

var result = client.CreateQuery<Information>("GetInformation")
             .AddQueryOption("id", string.Format("'{0}'", actualId))
             .Skip(index)
             .Take(amount).ToList();

I get this exception:

This target framework does not enable you to directly enumerate over a data service query. This is because enumeration automatically sends a synchronous request to the data service. Because this framework only supports asynchronous operations, you must instead call the BeginExecute and EndExecute methods to obtain a query result that supports enumeration.

As I had to use BeginExecute , I can no longer use Skip and Take .

var query = client.CreateQuery<Information>("GetInformation")
                  .AddQueryOption("id", string.Format("'{0}'", actualId));
query.BeginExecute((x) =>
          {
            var result= query.EndExecute(x);
            foreach (var information in result)
            {

            };                       
          }, null);

How should I do it with this asynchronous method?

Answer 1

I was having the same problem but with OData. I found the solution in the next blog http://jqyblogger.blogspot.com/2013/11/linq-query-error-message-on-windows.html and basically we need to use the asyncronus tools for OData.

            Default.Container context = new Default.Container(new Uri("url_to_OData_Service"));
        var nquery = context.Reports
                               .Where(r => r.ReportId == 1)
                               .Select(p => p);

        DataServiceQuery<Report> query = (DataServiceQuery<Report>)nquery;

        TaskFactory<IEnumerable<Report>> taskFactory = new TaskFactory<IEnumerable<Report>>();
        IEnumerable<Report> result = await taskFactory.FromAsync(query.BeginExecute(null, null), iar => query.EndExecute(iar));