Throw Exception in C++ App to call async method WinRT Component wirtten by C#

Question

Hi All,

My environment is Windows 8 Pro RTM  and VS 2012 RTM.

I have wirtten a WinRT Component by C# to access websites and to get the text content. I use C# app to call the async method which worked well. But when I use C++ app to call the method, it will throw an Exception:

+  &ThisException 0x0283e080 {ExceptionCode=0xe06d7363 ExceptionFlags=0x00000001 ExceptionRecord=0x00000000 {ExceptionCode=...} ...} EHExceptionRecord *

Below is my code. Would you please tell me the right way using C++ to call WinRT async method?

Thank you for your attention and I am looking forward to your reply.

WinRT Component: Service

namespace RtComponent
{
    internal class MyService
    {
        HttpClient httpClient;

        internal async Task<String> GetText()
        {
            httpClient = new HttpClient();

            HttpResponseMessage response = await httpClient.GetAsync("http://www.microsoft.com");

            String text = await response.Content.ReadAsStringAsync();

            return text;
        }
    }
}

WinRT Component: Feature

namespace RtComponent
{
    public sealed class MyFeature
    {
        public IAsyncOperation<String> GetText()
        {

            Service service = new Service();
            return Task.Run<String>(async () =>
                {
                    var data = await service.GetText();
                   
                    return data;                 
                }).AsAsyncOperation();
        }
     }
}

C# App : Work well

            MyFeature mf = new MyFeature();

            string str = await mf.GetText();

C++ App : Throw Excepiton

	IAsyncOperation<String^>^ Op = lb->GetText();
	String^ str = Op->GetResults();

Answer 1

you dont await in the c++ version. Now there is not an await keyword but there is a paattern to continue when the async task is complete.

take a look here:

http://msdn.microsoft.com/en-us/library/windows/apps/hh780559.aspx

Answer 2

Try these codes

 

create_task(lb->GetText()).then([](String^ str)

    {      

       String^ res=str;

    });

 

 

Best regards,

Jesse

---

Jesse Jiang [MSFT]
MSDN Community Support | Feedback to us

Answer 3

Hi Jesse,

It's worked. Thanks a lot!

Ning