You need to install `Microsoft.Extensions.Http` from [NuGet](
https://www.nuget.org/packages/Microsoft.Extensions.Http)

Aah, I have found the solution. I think `services.AddHttpClient` work with .net core 2.1. So I updated my .net core version to 2.1 and updated the microsoft packages to 2.1 and it starts working.

Getting the error message when using matplotlib:

&gt; Error #15: Initializing libiomp5.dylib, but found libiomp5.dylib
&gt; already initialized
&gt;     OMP: Hint: This means that multiple copies of the OpenMP runtime have been linked into the program. That is dangerous, since it can
&gt; degrade performance or cause incorrect results. The best thing to do
&gt; is to ensure that only a single OpenMP runtime is linked into the
&gt; process, e.g. by avoiding static linking of the OpenMP runtime in any
&gt; library. As an unsafe, unsupported, undocumented workaround you can
&gt; set the environment variable KMP_DUPLICATE_LIB_OK=TRUE to allow the
&gt; program to continue to execute, but that may cause crashes or silently
&gt; produce incorrect results. For more information, please see
&gt; http://www.intel.com/software/products/support/.



Error #15: Initializing libiomp5.dylib, but found libiomp5.dylib already initialized

Whenever I run `conda install/remove/update &lt;package&gt;`, it tells me it&#39;s &quot;Solving environment&quot; for some time before telling me the list of things it&#39;s going to download/install/update. Presumably it&#39;s looking for dependencies for `&lt;package&gt;`, but why does it sometimes *remove* packages after doing this operation? For example, as I was trying to install Mayavi, it decided it needed to remove Anaconda Navigator. 

Furthermore it does not provide an option to perform only a subset of the suggested operations. Is there a way to specify that I don&#39;t want a package removed?

What does conda do when &quot;solving environment&quot;

I am trying to use HttpClient in my .net core 2.0 project and for that I have injected HttpClient in my controller. But when I am trying to configure httpclient in my startup.cs I am getting this error: &quot;IServiceCollection does not contain a defintion for AddHttpClient&quot;. I have already referenced `using Microsoft.AspNetCore.Http;` and `using Microsoft.Extensions.DependencyInjection;` and here is what I am trying to do: 

    services.AddHttpClient&lt;TestController&gt;();

It&#39;s working fine in other project with same namespaces but here I am getting the error. Any help?

IServiceCollection does not contain a defintion for AddHttpClient

I am trying to use HttpClient in my .net core 2.0 project and for that I have injected HttpClient in my controller. But when I am trying to configure httpclient in my startup.cs I am getting this error: "IServiceCollection does not contain a defintion for AddHttpClient". I have already referenced <code>using Microsoft.AspNetCore.Http;</code> and <code>using Microsoft.Extensions.DependencyInjection;</code> and here is what I am trying to do:
<pre><code class="hljs language-ini">services.AddHttpClient&#x3C;TestController>();
</code></pre>
It's working fine in other project with same namespaces but here I am getting the error. Any help?

I am trying to inject dependency into my middleware constructor as follows

    public class CreateCompanyMiddleware
	{
	    private readonly RequestDelegate _next;
	    private readonly UserManager&lt;ApplicationUser&gt; _userManager;

	    public CreateCompanyMiddleware(RequestDelegate next
	        , UserManager&lt;ApplicationUser&gt; userManager
	        )
	    {
	        _next = next;
	    }

	    public async Task Invoke(HttpContext context)
	    {
	        await _next.Invoke(context);
	    }
	}

My Startup.cs file looks like

	public void ConfigureServices(IServiceCollection services)
    {
        services.AddDbContext&lt;ApplicationDbContext&gt;(options =&gt;
            options.UseMySql(Configuration.GetConnectionString(&quot;IdentityConnection&quot;)));

        services.AddIdentity&lt;ApplicationUser, IdentityRole&gt;()
            .AddEntityFrameworkStores&lt;ApplicationDbContext&gt;()
            .AddDefaultTokenProviders();
        ...

        app.UseMiddleware&lt;CreateCompanyMiddleware&gt;();

        ...

But I am getting this error

&gt; An error occurred while starting the application.
InvalidOperationException: Cannot resolve scoped service &#39;Microsoft.AspNetCore.Identity.UserManager`1[Common.Models.ApplicationUser]&#39; from root provider.
Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteValidator.ValidateResolution(Type serviceType, IServiceScope scope, IServiceScope rootScope)

How to do DI in asp.net core middleware?

I have 2 projects in my solution, I have a project with Entity Framework Core installed:

[![enter image description here][1]][1]

And in the other ASP.NET Web API project I have these packages:

    &lt;?xml version=&quot;1.0&quot; encoding=&quot;utf-8&quot;?&gt;
    &lt;packages&gt;
      &lt;package id=&quot;Antlr&quot; version=&quot;3.5.0.2&quot; targetFramework=&quot;net461&quot; /&gt;
      &lt;package id=&quot;Microsoft.ApplicationInsights&quot; version=&quot;2.5.1&quot; targetFramework=&quot;net461&quot; /&gt;
      &lt;package id=&quot;Microsoft.ApplicationInsights.Agent.Intercept&quot; version=&quot;2.4.0&quot; targetFramework=&quot;net461&quot; /&gt;
      &lt;package id=&quot;Microsoft.ApplicationInsights.DependencyCollector&quot; version=&quot;2.5.1&quot; targetFramework=&quot;net461&quot; /&gt;
      &lt;package id=&quot;Microsoft.ApplicationInsights.PerfCounterCollector&quot; version=&quot;2.5.1&quot; targetFramework=&quot;net461&quot; /&gt;
      &lt;package id=&quot;Microsoft.ApplicationInsights.Web&quot; version=&quot;2.5.1&quot; targetFramework=&quot;net461&quot; /&gt;
      &lt;package id=&quot;Microsoft.ApplicationInsights.WindowsServer&quot; version=&quot;2.5.1&quot; targetFramework=&quot;net461&quot; /&gt;
      &lt;package id=&quot;Microsoft.ApplicationInsights.WindowsServer.TelemetryChannel&quot; version=&quot;2.5.1&quot; targetFramework=&quot;net461&quot; /&gt;
      &lt;package id=&quot;Microsoft.AspNet.Mvc&quot; version=&quot;5.2.4&quot; targetFramework=&quot;net461&quot; /&gt;
      &lt;package id=&quot;Microsoft.AspNet.Razor&quot; version=&quot;3.2.4&quot; targetFramework=&quot;net461&quot; /&gt;
      &lt;package id=&quot;Microsoft.AspNet.TelemetryCorrelation&quot; version=&quot;1.0.0&quot; targetFramework=&quot;net461&quot; /&gt;
      &lt;package id=&quot;Microsoft.AspNet.Web.Optimization&quot; version=&quot;1.1.3&quot; targetFramework=&quot;net461&quot; /&gt;
      &lt;package id=&quot;Microsoft.AspNet.WebApi&quot; version=&quot;5.2.4&quot; targetFramework=&quot;net461&quot; /&gt;
      &lt;package id=&quot;Microsoft.AspNet.WebApi.Client&quot; version=&quot;5.2.4&quot; targetFramework=&quot;net461&quot; /&gt;
      &lt;package id=&quot;Microsoft.AspNet.WebApi.Core&quot; version=&quot;5.2.4&quot; targetFramework=&quot;net461&quot; /&gt;
      &lt;package id=&quot;Microsoft.AspNet.WebApi.HelpPage&quot; version=&quot;5.2.4&quot; targetFramework=&quot;net461&quot; /&gt;
      &lt;package id=&quot;Microsoft.AspNet.WebApi.WebHost&quot; version=&quot;5.2.4&quot; targetFramework=&quot;net461&quot; /&gt;
      &lt;package id=&quot;Microsoft.AspNet.WebPages&quot; version=&quot;3.2.4&quot; targetFramework=&quot;net461&quot; /&gt;
      &lt;package id=&quot;Microsoft.CodeDom.Providers.DotNetCompilerPlatform&quot; version=&quot;2.0.0&quot; targetFramework=&quot;net461&quot; /&gt;
      &lt;package id=&quot;Microsoft.Web.Infrastructure&quot; version=&quot;1.0.0.0&quot; targetFramework=&quot;net461&quot; /&gt;
      &lt;package id=&quot;Newtonsoft.Json&quot; version=&quot;11.0.1&quot; targetFramework=&quot;net461&quot; /&gt;
      &lt;package id=&quot;System.Diagnostics.DiagnosticSource&quot; version=&quot;4.4.1&quot; targetFramework=&quot;net461&quot; /&gt;
      &lt;package id=&quot;WebGrease&quot; version=&quot;1.6.0&quot; targetFramework=&quot;net461&quot; /&gt;
    &lt;/packages&gt;

When I run `Add-Migration` in PMC:

&gt; Your startup project &#39;API&#39; doesn&#39;t reference
&gt; Microsoft.EntityFrameworkCore.Design. This package is required for the
&gt; Entity Framework Core Tools to work. Ensure your startup project is
&gt; correct, install the package, and try again.

I installed Microsoft.EntityFrameworkCore.Design in the startup project instead of the data project that will contain all the entities and now it works, is this how the project should be setup?

  [1]: https://i.stack.imgur.com/p3cQA.png

Your startup project doesn&#39;t reference Microsoft.EntityFrameworkCore.Design

What is the possible cause of this error:

&gt; InvalidOperationException: No service for type &#39;Microsoft.AspNetCore.Identity.UserManager [Microsoft.AspNetCore.Identity.IdentityUser]&#39; has been registered.

My target framework is `netcoreapp2.1`.

This is my user store class:

    public class MyUserStore : IdentityUser
    {
        public string FirstName { get; set; }
        public string LastName { get; set; }
    }

And my user role class:

    public class MyUserRole : IdentityRole
    {
        public string Description { get; set; }
    }

My DbContext:

    public class ApplicationDbContext : IdentityDbContext&lt;MyUserStore,MyUserRole,string&gt;
    {
        public ApplicationDbContext(DbContextOptions&lt;ApplicationDbContext&gt; 
          options): base(options) { }
    }

My `ConfigureServices` method in `Startup.cs`:

    public void ConfigureServices(IServiceCollection services)
    {
        services.Configure&lt;CookiePolicyOptions&gt;(options =&gt;
        {
            // This lambda determines whether user consent for non-essential cookies is needed for a given request.
            options.CheckConsentNeeded = context =&gt; true;
            options.MinimumSameSitePolicy = SameSiteMode.None;
        });

        services.AddDbContext&lt;ApplicationDbContext&gt;(options =&gt;
            options.UseSqlServer(Configuration.GetConnectionString(&quot;DefaultConnection&quot;)));

        //services.AddDefaultIdentity&lt;IdentityUser&gt;()
        //    .AddEntityFrameworkStores&lt;ApplicationDbContext&gt;();

        services.AddIdentity&lt;MyUserStore, MyUserRole&gt;(cfg =&gt; {
            cfg.User.RequireUniqueEmail = true;
        }).AddEntityFrameworkStores&lt;ApplicationDbContext&gt;();
        services.AddTransient&lt;Seeder&gt;();
        services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1);
    }

i want to understand why this is happening and what is the best practice.

No service for type &#39;Microsoft.AspNetCore.Identity.UserManager`1[Microsoft.AspNetCore.Identity.IdentityUser]&#39; has been registered

I&#39;m in the process of migrating a project from Visual Basic to C# and I&#39;ve had to change how a `for` loop being used is declared.

In VB.NET the `for` loop is declared below:

&lt;!-- language: lang-vb --&gt;

    Dim stringValue As String = &quot;42&quot;

    For i As Integer = 1 To 10 - stringValue.Length
       stringValue = stringValue &amp; &quot; &quot; &amp; CStr(i)
       Console.WriteLine(stringValue)
    Next

Which outputs:

    42 1
    42 1 2
    42 1 2 3
    42 1 2 3 4
    42 1 2 3 4 5
    42 1 2 3 4 5 6
    42 1 2 3 4 5 6 7
    42 1 2 3 4 5 6 7 8

In C# the `for` loop is declared below:

    string stringValue = &quot;42&quot;;

    for (int i = 1; i &lt;= 10 - stringValue.Length; i ++)
    {
       stringValue = stringValue + &quot; &quot; + i.ToString();
       Console.WriteLine(stringValue);
    }

And the output:

    42 1
    42 1 2
    42 1 2 3

This obviously isn&#39;t correct so I had to change the code ever so slightly and included an integer variable that would hold the length of the string.

Please see the code below:

    string stringValue = &quot;42&quot;;
    int stringValueLength = stringValue.Length;

    for (int i = 1; i &lt;= 10 - stringValueLength; i ++)
    {
       stringValue = stringValue + &quot; &quot; + i.ToString();
       Console.WriteLine(stringValue);
    }

And the output:

    42 1
    42 1 2
    42 1 2 3
    42 1 2 3 4
    42 1 2 3 4 5
    42 1 2 3 4 5 6
    42 1 2 3 4 5 6 7
    42 1 2 3 4 5 6 7 8

Now my question resolves around how Visual Basic differs to C# in terms of Visual Basic using the `stringValue.Length` condition in the `for` loop even though each time the loop occurs the length of the string changes. Whereas in C# if I use the `stringValue.Length` in the `for` loop condition it changes the initial string value each time the loop occurs. Why is this?


Why does a for loop behave differently when migrating VB.NET code to C#?

I want to have a SPA that&#39;s doing all the work client side and even generating some graphs/visuals.

I&#39;d like to be able to have the user click buttons and save the visuals, tables, and other things from the page (that are both seen and not seen, so right click save or copy/paste is not always an option).

How do I call a function from the webassembly/blazor library, get it&#39;s results and save it as a file on the client side?

the idea is something like this...?

cshtml

    &lt;input type=&quot;file&quot; onchange=&quot;@ReadFile&quot;&gt;
    
    &lt;input type=&quot;file&quot; onchange=&quot;@SaveFile&quot;&gt;
    
    @functions{
    object blazorObject = new blazorLibrary.SomeObject();
    
    void ReadFile(){
        blazorObject.someFunction(...selectedFile?...);
        
    }
    void SaveFile(){
        saveFile(...selectedFile..?)
    }
    
    }



How can one generate and save a file client side using Blazor?

**AuthenticationRequiredAttribute Class** 


    public class AuthenticationRequiredAttribute : ActionFilterAttribute
    {
        ILoginTokenKeyApi _loginTokenKeyApi;
        IMemoryCache _memoryCache;

        public AuthenticationRequiredAttribute(IMemoryCache memoryCache)
        {
            _memoryCache = memoryCache;

            _loginTokenKeyApi = new LoginTokenKeyController(new UnitOfWork());
        }

        public override void OnActionExecuting(ActionExecutingContext filterContext)
        {
            var memory = _memoryCache.Get(Constants.KEYNAME_FOR_AUTHENTICATED_PAGES);

            string requestedPath = filterContext.HttpContext.Request.Path;

            string tokenKey = filterContext.HttpContext.Session.GetString(&quot;TokenKey&quot;)?.ToString();

            bool? isLoggedIn = _loginTokenKeyApi.IsLoggedInByTokenKey(tokenKey).Data;

            if (isLoggedIn == null ||
                !((bool)isLoggedIn) ||
                !Constants.AUTHENTICATED_PAGES_FOR_NORMAL_USERS.Contains(requestedPath))
            {
                filterContext.Result = new JsonResult(new { HttpStatusCode.Unauthorized });
            }
        }
        public override void OnActionExecuted(ActionExecutedContext filterContext)
        {
        }
    }

**HomeController**

    public class HomeController : Controller
    {
        IUserApi _userApi;
        ILoginTokenKeyApi _loginTokenKey;
        IMemoryCache _memoryCache;

        public HomeController(IUserApi userApi, ILoginTokenKeyApi loginTokenKey, IMemoryCache memoryCache)
        {
            _loginTokenKey = loginTokenKey;
            _userApi = userApi;

            _memoryCache = memoryCache;
        }

        [AuthenticationRequired] // There is AN ERROR !!
        public IActionResult Example()
        {
            return View();
        }
    }

ERROR : 

&gt; Error	CS7036	There is no argument given that corresponds to the
&gt; required formal parameter &#39;memoryCache&#39; of
&gt; &#39;AuthenticationRequiredAttribute.AuthenticationRequiredAttribute(IMemoryCache)&#39;	Project.Ground.WebUI

**My problem is actually : I cant use dependency injection in attribute classes**.

I want to use that attribute without any parameter. Is there any solution to solve it? I use dependency injection but it cant be used for attributes. How I can use it?

How can I use Dependency Injection in a .Net Core ActionFilterAttribute?

I&#39;ve configured my console application&#39;s `Main` like so

````csharp
var services = new ServiceCollection()
    .AddLogging(logging =&gt; logging.AddConsole())
    .BuildServiceProvider();
````

And then I try to use it in another class like so

````csharp
private readonly ILogger _logger;
    
public MyClass(ILogger logger)
{
    _logger = logger;
}

public void MyFunc()
{
    _logger.Log(LogLevel.Error, &quot;My Message&quot;);
}
````

&gt; System.InvalidOperationException: &#39;Unable to resolve service for type
&gt; &#39;Microsoft.Extensions.Logging.ILogger&#39;

I&#39;ve tried the solutions [here][1] but it didn&#39;t work for me.

**Edit**
Based on Yaakov&#39;s comment below and [this Github comment][2] I&#39;m able to resolve it correctly by doing this

````csharp
public MyClass(ILogger&lt;MyClass&gt; logger)
{
    _logger = logger;
}
````

I would have preferred to have this in the initial `BuildServiceProvider` but looks like I&#39;m gonna have to repeat this every time I want to use the logger (or create my own ILogger).


  [1]: https://stackoverflow.com/a/51329388/2025666
  [2]: https://github.com/domaindrivendev/Swashbuckle.AspNetCore/issues/92#issuecomment-223991293

Unable to resolve ILogger from Microsoft.Extensions.Logging

There is a framework-level navigation element at Microsoft Docs called [&quot;.NET Platform Extensions&quot;][1]. It contains docs on recently added APIs like `System.IO.Pipelines` and `System.Threading.Channels` for example, as well as a whole bunch of other APIs, including the not-so-recent ones.

Some APIs from this collection are available as nuget packages (for both .Net Core and .Net Framework), but others are not seemingly available. Also, as of now, there is no nuget package called &quot;.NET Platform Extensions&quot; or anything similar.

So, the question is what exactly does this collection of APIs represent? What is it&#39;s relationship to each of the following:

 - .Net Framework
 - .Net Core
 - .Net Standard

What about support in the .Net Framework / .Net Core?

Finally, some APIs seem to be already available as separate nuget packages, others are yet to be made available, so what is the story in that regard?

  [1]: https://docs.microsoft.com/en-us/dotnet/api/index?view=dotnet-plat-ext-2.1

What are .NET Platform Extensions on docs.microsoft.com?

I upgraded my project to .NET Core 2.2.x and got an obsolete warning regarding the following code - both lines:

    public void Configure(IApplicationBuilder app, 
                          IHostingEnvironment env, 
                          ILoggerFactory loggerFactory) 
      {
        loggerFactory.AddConsole(Configuration.GetSection(&quot;Logging&quot;));

The suggestion to fix is `The recommended alternative is AddConsole(this ILoggingBuilder builder)`.  I thought that is what I am using.

What am I missing here?

How to fix obsolete ILoggerFactory methods?

I have a .NET C# application and I would like to download the latest artifacts generated by the latest build of this public Azure DevOps project:

https://dev.azure.com/LumiaWoA/Boot%20Shim/_build?definitionId=3

How does one interface with Azure DevOps to download the artifacts for such a task? 

I have in mind to use an HttpClient to download the zipped artifacts using some special URL.

How to download the latest build artifacts from Azure DevOps programmatically?

I am using a third party library ([Splunk c# SDK][1] ) in my ASP.NET core application.  I am trying to connect to my localhost Splunk service via this SDK, but I get an exception saying: 

&gt; System.Net.Http.HttpRequestException: The SSL connection could not be established, see inner exception.

And The inner exception says:

&gt; The remote certificate is invalid according to the validation procedure.

This SDK uses HTTP client under the hood, but I don&#39;t have access to this object to configure HttpClientHandler.  

All my search on google ends up using ServicePointManager to bypass the SSL validation, but this solution doesn&#39;t work in Asp.Net core. 

    ServicePointManager.ServerCertificateValidationCallback = delegate { return true; };

Is there any way to bypass this validation in asp.Net core?

  [1]: http://dev.splunk.com/csharp

The SSL connection could not be established

ASP.NET Core 2.1.1 offers several seemingly related extension methods for appBuilder:

* `UseStaticFiles` from `Microsoft.AspNetCore.StaticFiles`
* `UseSpaStaticFiles` from `Microsoft.AspNetCore.SpaServices.Extensions`
* `UseSpa` from `Microsoft.AspNetCore.SpaServices.Extensions`

**Please help me make sense of their purpose and relation to each other?**

Also, is there any difference from the server execution standpoint if I run these methods in a different order 

e.g. 

    app.UseStaticFiles() -&gt; app.UseSpaStaticFiles() -&gt; app.UseSpa()

vs 

    app.UseSpa() -&gt; app.UseSpaStaticFiles() -&gt; app.UseStaticFiles()

Content Type	Original Author	Original Content on Stackoverflow
Question	Ask	View Question on Stackoverflow
Solution 1 - C#	Rahul Jain	View Answer on Stackoverflow
Solution 2 - C#	Ask	View Answer on Stackoverflow

IServiceCollection does not contain a defintion for AddHttpClient

C# Problem Overview

C# Solutions

Solution 1 - C#

Solution 2 - C#

What does conda do when "solving environment"

Error #15: Initializing libiomp5.dylib, but found libiomp5.dylib already initialized

Attributions