OK I've been playing with Silverlight and ran into something interesting that I hope someone can explain. The MSDN documentation clearly states that it has a WebRequest.GetResponse() Method. I have created some code to get the latest messages from twitter. The code works fine in a console app but I get an error when its in a silverlight app. The code is exactly the same, but in my xaml.cs file, the method seems to have disappeared from the framework. Anyone know why? Here are two screen shots showing you what I mean.
Console App: http://twitpic.com/bl6cf
Silverlight: http://twitpic.com/bl6ev
Silverlight Documentation does not list GetResponse() method because, In Silverlight you can call only BeginGetResponse method.
This is because you may block the UI thread and that may block the browser. BeginGetResponse is an asynchronous method.
Related
I just started learning UWP and i'm really confused on how it works. I already saw tens of posts that talk about my problem but can't figure out how to do what I want.
So I want to make an app that runs on windows startup, I want the app to be not visible so it needs a background Task, how can I trigger this background task without getting to the app UI ?
The app is supposed to have the Background Task always running, and its interface is supposed to be used as "settings" so I don't need the app to be shown on startup.
Thanks.
I found my way here after a lot of googling. to be honest I have come to the same conclusion as Motaz. But as of writing this I am way too invested in what I have already. While what I have here is not the perfect answer to his question. I wanted to come back and post what I've learned for anyone else who ends up here.
My need is a app that when started will monitor a third party USB device until the app is closed (regardless of whether the app is minimized or not)
Windows Template Studio is good, but the docs not so much. Especially when it comes to Background tasks.
I started here: https://github.com/Microsoft/Windows-universal-samples. But there is two problems.
They combined all the examples and some of the code is shared, which makes it difficult to pull a project out and hack it apart without breaking the original examples.
Following their background task example I perpetually had issue with the manifest and and it wanting an audio task
I went back to the template studio and created the simplest version with a background task possible. After a lot of trial and error I got something that works. I have posted it here: https://github.com/PillarOfSociety/WindowsTemplateStudio-BackgroundTask
Some things to note:
I am no expert on UWP and while this runs I have no intent on putting it in the store nor did I try.
If you do download my project and run it, you should be able to just hit the "Add events" and the "Start Back" button and the task should run and update the Progress bar.
I used an ApplicationTrigger. the original example from the template uses a TimeTrigger which takes time in MINUTES (took me too long to figure that out). Supposedly Application triggers have a 30sec timeout.. but on my laptop they live for much longer.. I don't know how long. This page is useful: https://learn.microsoft.com/en-us/windows/uwp/launch-resume/support-your-app-with-background-tasks
The template studio generated BackgroundTaskService will leave background tasks registered after the app is closed, but will NOT make the connection back to them once its rerun, so on a rerun either the task appears not to run, or will crash the app when triggered.
Important Code I discovered:
foreach (var task in BackgroundTaskRegistration.AllTasks)
{
TestText += task.Value.Name; //gets the typename of the task
//task.Value.Unregister(true); //will unregister tasks
}
await Task.CompletedTask;
The tasks in BackgroundTaskRegistration.AllTasks are not the BackgroundTask class that the template studio uses. IN my example I unregister all of them each time it runs so that you have a reference to the task as an instance of BackgroundTask.
Hopefully this helps someone and Good luck!
If you're just starting out use Windows Template Studio, it will be perfect for you. It is an extension of Visual Studio which lets you create new uwp projects with a lot of built in features, and you can only choose the features you want. It will save you a lot of time on basic stuff.
https://github.com/Microsoft/WindowsTemplateStudio
I was in the middle of developing an update to my Xamarin Forms app, but when I debugged it on my iPhone, it crashed immediately on startup with the following message:
Assertion failure in -[UIApplication_runWithMainScene:transitionContext:completion:], /BuildRoot/Library/Caches/com/apple.xbs/Source/UIKit/UIKit-3600.5.2/UIApplication.m:3679
It was previously working fine, but now I can't run the app on my phone anymore without this crash. I have rebuilt several times and deployed from different computers, but nothing helps. How do I fix this issue?
Edit:
Before this started occurring, I had made some additions to the code. Unfortunately, after removing all of my changes, this issue is still plaguing further development. Any help or resource that might lead me to a solution will be greatly appreciated.
After some deep searching, it turns out that I mistakenly removed a part of my Application's constructor that initialized the MainPage. As a result, MainPage remained null. The framework probably tried to call a method or access a property without checking if the reference was null, causing the error. I'm not sure how long that mistake has been there.
This can also happen if you are not quick to launch a view. Avoid calling APIs or other lengthy processes before a page is displayed for the first time. You may do that in parallel but not in the same thread that launches the page.
I am trying to take a photo during a BackgroundTask at an UWP application.
I read at documentation that InitializeAsync should be on the STA thread but is there some approach to achieve that from a MTA? I don't known, something like Dispatchers or others workarounds.
In my actual scenario, when I call CapturePhotoToStreamAsync just after the InitializeAsync, the following exception occurs:
System.Runtime.InteropServices.COMException (0xC00D3E82): A media
source cannot go from the stopped state to the paused state.
The funny thing is that it works if my app is not suspended.
I don't think you will get it to work in BackgroundTask - as MSDN says:
InitializeAsync should be called from the main UI thread of your app. For more information, see Guidelines for enabling sensitive devices.
We are currently trying to incorporate Lync communication (Lync SDK 2010) into our application and we have run into an issue with the VideoWindows (CaptureVideoWindow, RenderVideoWindow) of the AVModality's VideoChannel: They are always null, even after successfully calling BeginStart. The connection is definitely established. We can talk. Our own video is shown in a remote Lync client. AVModalityState is Connected. VideoChannelState goes from Connecting to Receive to Send.
It does not matter when and how we try to access them: Directly after BeginStart, in the AsyncCallback of BeginStart, in response to various state changes or in response to an external trigger (user click event); in the main/UI thread or in an event/callback thread. The two video windows are always null.
In the example application "%PROGRAMFILES%\Microsoft Lync\SDK\Samples\AudioVideoConversation", everything works as intended: As soon as BeginStart has finished, we can access the non-null video windows. In our little stand-alone prototype project, it works, too. But in our real application, it does not.
We have double checked everything and we have really run out of ideas of what might cause this problem.
Any ideas, any hints? Anything that we should be aware of?
(Link to corresponding MSDN forum thread)
Update (4th July 2012, 15:46 CET):
When we take a look at the members of the VideoChannel we find that internally a COMException occured in "Microsoft.Office.Uc": Error loading DLL, HRESULT: 0x80029C4A (TYPE_E_CANTLOADLIBRARY). More details in the attached screenshot.
We did some research on this error, but found nothing that worked for us. Any ideas what causes the Exception?
Update (9th July 2012, 16:43 CET):
We did some further testing...
Our software consists of one main application and many plugin-like "apps" loaded via MEF. We created a minimal test app that makes a video call: The video windows did not work (as expected). But when we took the identical code and created a separate solution outside of our architecture, then it did work. So, it was an issue with the environment, not the code.
At first, we suspected MEF might be the problem. So, we hacked the lync code into our main application - circumventing the whole app architecture. Still not working.
Then we sliced off our whole system, bit by bit, until we finally reached a point where it did work. After following wrong tracks several times, we finally found the culprit... Quartz.NET!
For some strange reason the mere presence of an assembly reference to the Quartz.dll v.1.0.3.3, even without a single line of Quartz code, causes the video windows to not work. Unbelievable, but it's 100% reproducible: If we take the previously mentioned test solution and do nothing but add the reference, it stops working.
Any idea how such a thing is possible?
We solved it! Kind of. A reference to a Quartz.NET DLL somehow caused the issue. More details in the updated question.
For now, we have removed the component that used Quartz. We currently do not need it.
But I'm still interested in further input how a mere reference can cause such an issue.
I've tried to read up on a few articles about this, but some of them were over my head at the moment.
I run a program that re-caches some SQL data from an external source. I call this from a WinForm application which manipulates the aforementioned data.
While the Console app is running, I lay over the controls with a panel (with a textbox on it) and try to capture the Console app's stdout into the textbox. It "works", but has some issues with repeating lines and missing lines. Reading the stream after the process ends works fine, but I'm having issues with real-time.
CODE
It worked well for me in asynchronous way. Unfortunately I'm not so familiar with .net to write code from my memory...
Upd:
Spent a couple of minutes and found the page in MSDN. Use Process.BeginOutputReadLine Method, here is the description of the function and a sample of its usage.