I think you might be looking for `[FromQuery]`:
https://docs.microsoft.com/en-us/aspnet/core/mvc/models/model-binding#customize-model-binding-behavior-with-attributes

`[FromUri]` is used in Asp.Net WebApi 2, not asp.net core

**TLDR** : You can use **`[FromQuery]`** and **`[FromRoute]`** in place of `[FromUri]`

&lt;hr&gt;

As Mike_G stated in his [answer][1] you can use `[FromQuery]` attribute in place of `[FromUri]`. But you might also need to use `[FromRoute]` in certain cases as pointed by [Muhammad Umar][2] in comments.

[**FromRoute**][3]

This attribute is used when the parameter is passed as the part of the URL string.

Ex: `api/countries/1`

[**FromQuery**][4]

As the name implies, FromQuery parameters has to be passed as query strings.

Ex: `api/countries?id=1`

**References:**

 1. [FromRoute - Microsoft Docs][3]
 2. [FromQuery - Microsoft Docs][4]
 3. [FromUri - Microsoft Docs][5]


  [1]: https://stackoverflow.com/a/48195125/5407188
  [2]: https://stackoverflow.com/users/2219414/muhammad-umar
  [3]: https://docs.microsoft.com/en-us/dotnet/api/microsoft.aspnetcore.mvc.fromrouteattribute
  [4]: https://docs.microsoft.com/en-us/dotnet/api/microsoft.aspnetcore.mvc.fromqueryattribute
  [5]: https://docs.microsoft.com/en-us/aspnet/web-api/overview/formats-and-model-binding/parameter-binding-in-aspnet-web-api#using-fromuri

I am in the progress of learning through Java 8 lambda expressions and would like to ask about the following piece of Java code relating to the [`peek`][peek] method in the function interface that I have come across.

On execution of the program on IDE, it gives no output. I was expecting it would give `2, 4, 6`.

    import java.util.Arrays;
    import java.util.List;
    
    public class Test_Q3 {

	    public Test_Q3() {
	    }

	    public static void main(String[] args) {
            List&lt;Integer&gt; values = Arrays.asList(1, 2, 3);
		    values.stream()
		          .map(n -&gt; n * 2)
		          .peek(System.out::print)
		          .count();
	    }
    }

[peek]: https://docs.oracle.com/javase/9/docs/api/java/util/stream/Stream.html#peek-java.util.function.Consumer-


Stream.peek() method in Java 8 vs Java 9

I&#39;m using Android MVVM architecture with LiveData. I have an object like this

    public class User {
        private String firstName;
        private String lastName;

        public String getFirstName() {
            return firstName;
        }

        public void setFirstName(String firstName) {
            this.firstName = firstName;
        }

        public String getLastName() {
            return lastName;
        }

        public void setLastName(String lastName) {
            this.lastName = lastName;
        }
    }

And my view model looks like this 

    public class InfoViewModel extends AndroidViewModel {
        MutableLiveData&lt;User&gt; user = new MutableLiveData&lt;&gt;();

        public InfoViewModel(@NonNull Application application) {
            super(application);
            User user = new User();
            user.setFirstName(&quot;Alireza&quot;);
            user.setLastName(&quot;Ahmadi&quot;);

            this.user.setValue(user);
        }

        public LiveData&lt;User&gt; getUser(){
            return user;
        }

        public void change(){
            user.getValue().setFirstName(user.getValue().getFirstName() + &quot; A &quot;);
        }
    }

How can I make sure when some field in user object changes observers get notified? BTW it is important to me to keep this data in the separate object and not use primary values like Strings in my ViewModel.


LiveData update on object field change

This question is because in my MVC project with **ASP.NET CORE 2.0**, I can not add the `[FromUri] attribute` to my drivers.

I tried using libraries like `System.Web.Http`, but I did not recognize them. Then install these from Nuget `Microsoft.AspNet.WebApi.Core` &quot;and&quot; `System.AppDomain.NetCoreApp`, which resulted in being able to use `System.Web.Http` but due to ambiguity problems I was not allowed to use it, but if I found that `[FromUri]` existed.


The main question is whether in ASP.NET core 2.0 MVC or WebApi exists `[FromUri]` ?

if it exists, how to use it?

FromUri in ASP.NET CORE 2.0

This question is because in my MVC project with ASP.NET CORE 2.0, I can not add the <code>[FromUri] attribute</code> to my drivers.
I tried using libraries like <code>System.Web.Http</code>, but I did not recognize them. Then install these from Nuget <code>Microsoft.AspNet.WebApi.Core</code> "and" <code>System.AppDomain.NetCoreApp</code>, which resulted in being able to use <code>System.Web.Http</code> but due to ambiguity problems I was not allowed to use it, but if I found that <code>[FromUri]</code> existed.
The main question is whether in ASP.NET core 2.0 MVC or WebApi exists <code>[FromUri]</code> ?
if it exists, how to use it?

**The question: Should I use .Net Core Identity or IdentityServer 4 with Identity**

I need to build app with login/register functionality and allow users to use APIs to import/export data from my software. I also want to have external logins like google, twitter, etc.

And I&#39;m not able to understand why would I need Identity Server when all things can be done using only Identity. 

Why would I need or want IdentityServer ? I just need to get work done right and  as simple as possible.

.NET Core Identity vs IdentityServer4

### Question

How should I inject (using the standard dependency injection) a `DbContext` instance into a `IHostedService`?

### What have I tried

I currently have my `IHostedService` class take a `MainContext` (deriving from `DbContext`) instance in the constructor.

When I run the application I get:

&gt; Cannot consume scoped service &#39;Microsoft.EntityFrameworkCore.DbContextOptions&#39; from singleton &#39;Microsoft.Extensions.Hosting.IHostedService&#39;.

So I tried to make the `DbContextOptions` transient by specifying:

    services.AddDbContext&lt;MainContext&gt;(options =&gt; 
                    options.UseSqlite(&quot;Data Source=development.db&quot;), ServiceLifetime.Transient);

in my `Startup` class.

But the error remains the same, even though, according to [this solved Github issue](https://github.com/aspnet/EntityFrameworkCore/issues/6863) the `DbContextOptions` passed should have the same lifetime specified in the `AddDbContext` call.

I can&#39;t make the database context a singleton otherwise concurrent calls to it would yield concurrency exceptions (due to the fact that the database context is not guaranteed to be thread safe).

How should I inject a DbContext instance into an IHostedService?

For Asp.net Core apps, which one do we have to use? `AddDbContext` or `AddDbContextPool`? According to EF Core documentation, `AddDbContextPool` provides high performance but the default Asp.net Core project templates use `AddDbContext`. 




AddDbContext or AddDbContextPool

I am having trouble getting the Swashbuckle.AspNetCore (1.0.0) package to generate any output.  I read the swagger.json file should be written to &#39;~/swagger/docs/v1&#39;.  However, I am not getting any output.

I started with a brand new ASP.NET Core API project. I should mention this is ASP.NET Core 2. The API works, and I am able to retrieve values from the values controller just fine.  

My startup class has the configuration exactly as described in this article ([Swashbuckle.AspNetCore on GitHub][1]).

    public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddMvc();

            services.AddSwaggerGen(c =&gt;
            {
                c.SwaggerDoc(&quot;v1&quot;, new Info { Title = &quot;My API&quot;, Version = &quot;v1&quot; });
            });
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IHostingEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();

                // Enable middleware to serve generated Swagger as a JSON endpoint.
                app.UseSwagger();
                app.UseSwaggerUI(c =&gt;
                {
                    c.SwaggerEndpoint(&quot;/swagger/v1/swagger.json&quot;, &quot;MyAPI V1&quot;);
                });
            }
            else
            {
                app.UseExceptionHandler();
            }

            app.UseStatusCodePages();
            app.UseMvc();

            //throw new Exception();
        }
    }

You can see the NuGet references...

[![enter image description here][2]][2]

Again, this is all the default template, but I include the ValuesController for reference...

    [Route(&quot;api/[controller]&quot;)]
    public class ValuesController : Controller
    {
        // GET api/values
        [HttpGet]
        public IEnumerable&lt;string&gt; Get()
        {
            return new string[] { &quot;value1&quot;, &quot;value2&quot; };
        }

        // GET api/values/5
        [HttpGet(&quot;{id}&quot;)]
        public string Get(int id)
        {
            return &quot;value&quot;;
        }

        // POST api/values
        [HttpPost]
        public void Post([FromBody]string value)
        {
        }

        // PUT api/values/5
        [HttpPut(&quot;{id}&quot;)]
        public void Put(int id, [FromBody]string value)
        {
        }

        // DELETE api/values/5
        [HttpDelete(&quot;{id}&quot;)]
        public void Delete(int id)
        {
        }
    }


  [1]: https://github.com/domaindrivendev/Swashbuckle.AspNetCore
  [2]: https://i.stack.imgur.com/WYiRf.png

ASP.NET Core - Swashbuckle not creating swagger.json file

I want to update Bootstrap in ASP.NET Core with NuGet. I used this:

    Install-Package bootstrap -Version 4.0.0

It did add the dependencies but how do I add it to my project now? What is the path for local NuGet dependencies?

![Installed NuGet dependencies](https://i.stack.imgur.com/J7fL6.png)

How to use Bootstrap 4 in ASP.NET Core

When I try to run my app I get the error 

    InvalidOperationException: Cannot resolve &#39;API.Domain.Data.Repositories.IEmailRepository&#39; from root provider because it requires scoped service &#39;API.Domain.Data.EmailRouterContext&#39;.

What&#39;s odd is that this EmailRepository and interface is set up exactly the same as far as I can tell as all of my other repositories yet no error is thrown for them.  The error only occurs if I try to use the app.UseEmailingExceptionHandling(); line. Here&#39;s some of my Startup.cs file.


    public class Startup
    {
        public IConfiguration Configuration { get; protected set; }
        private APIEnvironment _environment { get; set; }
    
        public Startup(IConfiguration configuration, IHostingEnvironment env)
        {
            Configuration = configuration;
    
            _environment = APIEnvironment.Development;
            if (env.IsProduction()) _environment = APIEnvironment.Production;
            if (env.IsStaging()) _environment = APIEnvironment.Staging;
        }
    
        public void ConfigureServices(IServiceCollection services)
        {
            var dataConnect = new DataConnect(_environment);
    
            services.AddDbContext&lt;GeneralInfoContext&gt;(opt =&gt; opt.UseSqlServer(dataConnect.GetConnectString(Database.GeneralInfo)));
            services.AddDbContext&lt;EmailRouterContext&gt;(opt =&gt; opt.UseSqlServer(dataConnect.GetConnectString(Database.EmailRouter)));
    
            services.AddWebEncoders();
            services.AddMvc();
    
            services.AddScoped&lt;IGenInfoNoteRepository, GenInfoNoteRepository&gt;();
            services.AddScoped&lt;IEventLogRepository, EventLogRepository&gt;();
            services.AddScoped&lt;IStateRepository, StateRepository&gt;();
            services.AddScoped&lt;IEmailRepository, EmailRepository&gt;();
        }
    
        public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
        {
            loggerFactory.AddConsole();
    
            app.UseAuthentication();
    
            app.UseStatusCodePages();
            app.UseEmailingExceptionHandling();
    
            app.UseMvcWithDefaultRoute();
        }
    }

Here is the EmailRepository

    public interface IEmailRepository
    {
        void SendEmail(Email email);
    }
    
    public class EmailRepository : IEmailRepository, IDisposable
    {
        private bool disposed;
        private readonly EmailRouterContext edc;
    
        public EmailRepository(EmailRouterContext emailRouterContext)
        {
            edc = emailRouterContext;
        }
    
        public void SendEmail(Email email)
        {
            edc.EmailMessages.Add(new EmailMessages
            {
                DateAdded = DateTime.Now,
                FromAddress = email.FromAddress,
                MailFormat = email.Format,
                MessageBody = email.Body,
                SubjectLine = email.Subject,
                ToAddress = email.ToAddress
            });
            edc.SaveChanges();
        }
    
        public void Dispose()
        {
            Dispose(true);
            GC.SuppressFinalize(this);
        }
    
        private void Dispose(bool disposing)
        {
            if (!disposed)
            {
                if (disposing)
                    edc.Dispose();
                disposed = true;
            }
        }
    }

And finally the exception handling middleware

    public class ExceptionHandlingMiddleware
    {
        private const string ErrorEmailAddress = &quot;errors@ourdomain.com&quot;;
        private readonly IEmailRepository _emailRepository;
    
        private readonly RequestDelegate _next;
    
        public ExceptionHandlingMiddleware(RequestDelegate next, IEmailRepository emailRepository)
        {
            _next = next;
            _emailRepository = emailRepository;
        }
    
        public async Task Invoke(HttpContext context)
        {
            try
            {
                await _next.Invoke(context);
            }
            catch (Exception ex)
            {
                await HandleExceptionAsync(context, ex, _emailRepository);
            }
        }
    
        private static Task HandleExceptionAsync(HttpContext context, Exception exception,
            IEmailRepository emailRepository)
        {
            var code = HttpStatusCode.InternalServerError; // 500 if unexpected
    
            var email = new Email
            {
                Body = exception.Message,
                FromAddress = ErrorEmailAddress,
                Subject = &quot;API Error&quot;,
                ToAddress = ErrorEmailAddress
            };
    
            emailRepository.SendEmail(email);
    
            context.Response.ContentType = &quot;application/json&quot;;
            context.Response.StatusCode = (int) code;
            return context.Response.WriteAsync(&quot;An error occured.&quot;);
        }
    }
    
    public static class AppErrorHandlingExtensions
    {
        public static IApplicationBuilder UseEmailingExceptionHandling(this IApplicationBuilder app)
        {
            if (app == null)
                throw new ArgumentNullException(nameof(app));
            return app.UseMiddleware&lt;ExceptionHandlingMiddleware&gt;();
        }
    }

Update:
I found this link https://github.com/aspnet/DependencyInjection/issues/578 which led me to change my Program.cs file&#39;s BuildWebHost method from this

    public static IWebHost BuildWebHost(string[] args)
    {
        return WebHost.CreateDefaultBuilder(args)
            .UseStartup&lt;Startup&gt;()
            .Build();
    }

to this

    public static IWebHost BuildWebHost(string[] args)
    {
        return WebHost.CreateDefaultBuilder(args)
            .UseStartup&lt;Startup&gt;()
            .UseDefaultServiceProvider(options =&gt;
                options.ValidateScopes = false)
            .Build();
    }

I don&#39;t know what exactly is going on but it seems to work now.

Cannot resolve scoped service from root provider .Net Core 2

I am having a few issues with EF Core at the moment. I have some data that I need to delete, and I am struggeling to see how the fluent API works, exactly in regards to the `.OnDelete()` function.

Considering the classic blog/post scenario from [microsofts own websites][1], I wonder what entity, exactly the `OnDelete()` is &#39;targeting&#39; (for the lack of a better word) In some instances it seems to be the blog, in others, the post. Can the Cascade delete be defined from both sides (that the posts are deleted when the parent Blog is) if so i imagine the code should look like this:

`model.Entity&lt;Post&gt;().HasOne(p =&gt; p.Blog).WithMany(b =&gt; b.Posts).HasForeignKey(p =&gt; p.BlogId).OnDelete(DeleteBehavior.Cascade)`

As i understand this is saying &quot;When a Blog is deleted, first delete all posts referencing this blog&quot; meaning the `OnDelete(DeleteBehavior.Cascade)`applies to blog, not to post.

But is this the same then?

`model.Entity&lt;Blog&gt;().HasMany(b =&gt; b.Posts).WithOne(p =&gt; p.Blog).OnDelete(DeleteBehavior.Cascade)`

or does `OnDelete(DeleteBehavior.Cascade)` apply to Post rather than blog?


  [1]: https://docs.microsoft.com/en-us/ef/core/saving/cascade-delete

Cascade deleting with EF Core

I have a question regarding authentication in ASP.NET Core 2: what exactly is the call **app.UseAuthentication()** for? 

Is it a basic prerequisite so that I can implement my custom authentication logic? I already had a look at the implementation of [UseAuthentication][1] and also of the actual middleware [AuthenticationMiddleware][2], but to be honest, I don&#39;t understand what that is actually doing and why it would be necessary. 

To put it in another way: 

Do I need to call **UseAuthentication()**
[![enter image description here][3]][3]

or is it a nice-to-have and I can do my custom auth anyways?
[![enter image description here][4]][4]

If I was fine without calling **UseAuthentication()** I&#39;d still be interested in what [AuthenticationMiddleware][2] is actually doing. So if you knew that I&#39;d be very grateful if you could explain it for me as well. 



  [1]: https://github.com/aspnet/Security/blob/dev/src/Microsoft.AspNetCore.Authentication/AuthAppBuilderExtensions.cs
  [2]: https://github.com/aspnet/Security/blob/1c30f33c925a97b105b3f9d34497218b0c9342b6/src/Microsoft.AspNetCore.Authentication/AuthenticationMiddleware.cs
  [3]: https://i.stack.imgur.com/MYmlo.png
  [4]: https://i.stack.imgur.com/BhaxK.png

Content Type	Original Author	Original Content on Stackoverflow
Question	Alexis Zapata	View Question on Stackoverflow
Solution 1 - asp.net Core	Mike_G	View Answer on Stackoverflow
Solution 2 - asp.net Core	Kolappan N	View Answer on Stackoverflow

FromUri in ASP.NET CORE 2.0

asp.net Core Problem Overview

asp.net Core Solutions

Solution 1 - asp.net Core

Solution 2 - asp.net Core

LiveData update on object field change

Stream.peek() method in Java 8 vs Java 9

Attributions