async-await

问题 I want to instantiate a ContentDialog in my UWP app, which is defined in my XAML as follows: <Page . . . <Grid x:Name="grd"> . . . <ContentDialog x:Name="cntDlgLoadMap" Title="This is an example" PrimaryButtonText="Ok" CloseButtonText="Cancel" DefaultButton="Primary"> </ContentDialog> </Grid> </Page> Trying to get a minimal example running, I was going to try this: private void btnLoadMap_Click(object sender, RoutedEventArgs e) { cntDlgLoadMap.ShowAsync(); } ...but got this design-time err

问题 I want to instantiate a ContentDialog in my UWP app, which is defined in my XAML as follows: <Page . . . <Grid x:Name="grd"> . . . <ContentDialog x:Name="cntDlgLoadMap" Title="This is an example" PrimaryButtonText="Ok" CloseButtonText="Cancel" DefaultButton="Primary"> </ContentDialog> </Grid> </Page> Trying to get a minimal example running, I was going to try this: private void btnLoadMap_Click(object sender, RoutedEventArgs e) { cntDlgLoadMap.ShowAsync(); } ...but got this design-time err

问题 I want to instantiate a ContentDialog in my UWP app, which is defined in my XAML as follows: <Page . . . <Grid x:Name="grd"> . . . <ContentDialog x:Name="cntDlgLoadMap" Title="This is an example" PrimaryButtonText="Ok" CloseButtonText="Cancel" DefaultButton="Primary"> </ContentDialog> </Grid> </Page> Trying to get a minimal example running, I was going to try this: private void btnLoadMap_Click(object sender, RoutedEventArgs e) { cntDlgLoadMap.ShowAsync(); } ...but got this design-time err

问题 Function need to return Task<List<Record>> Following both options are returning Task<List<Record>> , which one is more efficient? Is there any standard way here? Option 1 : Task<List<Record>> GetRecords() { return DbContext.Set<Record>.Where(predicate).ToListAsync(); } Option 2: Task<List<Record>> GetRecords() { return DbContext.Set<Record>.Where(predicate).AsAsyncEnumerable().ToList(); } 回答1: Go for option 1 ToListAsync as the source code of AsAsyncEnumerable explicitly mentions This is an

问题 Possible duplicate of await is only valid in async function. I am new to NodeJS and I found the concept of async-await a bit confusing. After some reading and muddling around, this is my understanding of the same. Suppose, I have a function sum like this. function sum(a, b) { // print the numbers for (var i = 0; i < 100000; i++) { console.log(i); } // settimeout new Promise (resolve => { setTimeout(resolve, 1000); }); return a+b; } function main() { let a = sum(5,2); console.log(a); } main();

问题 Goal: I am confused by the behavior I am seeing with exceptions in my .Net Core library. The goal of this question is to understand why it is doing what I am seeing. Executive Summary I thought that when an async method is called, the code in it is executed synchronously until it hits the first await. If that is the case, then, if an exception is thrown during that "synchronous code", why is it not propagated up to the calling method? (As a normal synchronous method would do.) Example Code:

问题 Goal: I am confused by the behavior I am seeing with exceptions in my .Net Core library. The goal of this question is to understand why it is doing what I am seeing. Executive Summary I thought that when an async method is called, the code in it is executed synchronously until it hits the first await. If that is the case, then, if an exception is thrown during that "synchronous code", why is it not propagated up to the calling method? (As a normal synchronous method would do.) Example Code:

问题 Consider a scenario where you have some asynchronous work to be done and you can run it in a fire and forget mode. This asynchronous work is able to listen for cancellation and so you pass it a cancellation token in order to being able to cancel it. At a given moment in time we can decide to request the cancellation of the ongoing activity, by using the cancellation token source object from which we have taken the cancellation token. Because cancellation token source implements IDisposable ,

问题 Consider a scenario where you have some asynchronous work to be done and you can run it in a fire and forget mode. This asynchronous work is able to listen for cancellation and so you pass it a cancellation token in order to being able to cancel it. At a given moment in time we can decide to request the cancellation of the ongoing activity, by using the cancellation token source object from which we have taken the cancellation token. Because cancellation token source implements IDisposable ,

问题 Consider a scenario where you have some asynchronous work to be done and you can run it in a fire and forget mode. This asynchronous work is able to listen for cancellation and so you pass it a cancellation token in order to being able to cancel it. At a given moment in time we can decide to request the cancellation of the ongoing activity, by using the cancellation token source object from which we have taken the cancellation token. Because cancellation token source implements IDisposable ,