markjprice/cs7dotnetcore2

Repository for the Packt Publishing book titled "C# 7.1 and .NET Core 2.0" by Mark J. Price

cs7dotnetcore2

Warning! .NET Core 2.1 reaches End of Support on August 21, 2021. https://devblogs.microsoft.com/dotnet/net-core-2-1-will-reach-end-of-support-on-august-21-2021/

C# 7.1 and .NET Core 2.0: Modern Cross-Platform Development, Third Edition

cs7dotnetcore2's Issues

Solutions to exercises

Hi Mark, you mentioned that readers can find all solutions to the exercises for this book in this repo, however, I looked through all the folders couldn't find them. Could you tell me where can I find the solutions?

Windows 10: 'git clone' - Error: invalid path 'VSCode/Part3/NorthwindWeb/..\Northwind.db'

Error while git cloning to local repo.

Problem with file name '..\Northwind.db'

Workaround: rename '..\Northwind.db' to 'Northwind.db'

GetStreamAsync().Result hangs UI thread.

Hi Mark,

I believe code in CategoriesViewModel that asks for service response is very bad example and shouldn't be shown as such. Generally we shouldn't await in UI thread. UI should be responsive.
From my perspective this example works only because HTTP response is from localhost, not remote server. Just add Thread.Sleep(5000) and see app hang for 5 seconds.

There are many articles on the internet treating this as potential UI deadlock situation, example:
https://medium.com/bynder-tech/c-why-you-should-use-configureawait-false-in-your-library-code-d7837dce3d7f
For me it was only long await time, not a deadlock but still.

I believe the right solution is to firstly create empty ObservableCollection. Then, create simple task (important it's worker, not UI thread) and run code that's in constructor. No awaits. When request is completed fill Categories collection (still in task) using CoreApplication.MainView.Dispatcher.RunAsync to access it via UI thread.
Since it is ObservableCollection once task is finished collection will be updated automatically.

Hope it helps,
Myfero

Part3 : The customers list only shown once and disappeared

In the part 3:
The response of customers data only shown once and disappeared.
I saw the error message like the following:

No 'Access-Control-Allow-Origin' header is present on the requested resource.

I tested the snippet on the book

public void ConfigureServices(IServiceCollection services)
        {
services.AddCors();

..}

public void Configure(IApplicationBuilder app, IHostingEnvironment env)
        {
  app.UseCors(c=>c.WithOrigins("Http://localhost:5002"));
  //          app.UseCors("AllowAllOrigins");
            app.UseMvc();
}

I cannot get the customers' data.help please, thanks!