You can replace the compiler shipped with Visual Studio for a C# 7-enabled version by installing the Nuget package [Microsoft.Net.Compilers][1]:

&gt; Referencing this package will cause the project to be built using the
&gt; specific version of the C# and Visual Basic compilers contained in the
&gt; package, as opposed to any system installed version.

There is no indication that I can see on the package page as to whether this is officially supported in Visual Studio 2015. My not-thorough tests so far indicate that it works but not painlessly - C# 7 code compiles, but is underlined with the red squiggly line which indicates a syntax error:
[![Screenshot][2]][2]Note that you will also need to install the Nuget package [System.ValueTuple][3] to use the new C# 7 value tuples features.


  [1]: https://www.nuget.org/packages/Microsoft.Net.Compilers/
  [2]: https://i.stack.imgur.com/kTxI5.png
  [3]: https://www.nuget.org/packages/System.ValueTuple/

In my case, installing just &lt;i&gt;Microsoft.Net.Compilers&lt;/i&gt; didn&#39;t work. Instead, I had to do the following: 
&lt;ol&gt;
&lt;li&gt;Install &lt;b&gt;Microsoft.CodeDom.Providers.DotNetCompilerPlatform&lt;/b&gt; for the project (&lt;i&gt;Tools&lt;/i&gt; =&gt; &lt;i&gt;NuGet Package Manager&lt;/i&gt; =&gt; &lt;i&gt;Manage Nuget Packages for Solution...&lt;/i&gt;) and install &lt;i&gt;Microsoft.CodeDom.Providers.DotNetCompilerPlatform&lt;/i&gt;.&lt;/li&gt;&lt;li&gt;Install the latest &lt;b&gt;Microsoft.Net.Compilers&lt;/b&gt; for the project&lt;/li&gt;
&lt;li&gt;Install any other NuGet package for the latest C# feature you want to use. In my case, my goal was to use Tuples, so I installed &lt;i&gt;System.ValueTuple&lt;/i&gt; and worked fine.&lt;/li&gt;
&lt;/ol&gt;
But still note that C# codes which are not known by Visual Studio 2015 default compiler will still have  red squiggles underneath. 

I have a case where in my `Vue.js` with `webpack` web app, I need to display dynamic images. I want to show `img` where file name of images are stored in a variable. That variable is a `computed` property which is returning a `Vuex` store variable, which is being populated asynchronously on `beforeMount`.

    &lt;div class=&quot;col-lg-2&quot; v-for=&quot;pic in pics&quot;&gt;
       &lt;img v-bind:src=&quot;&#39;../assets/&#39; + pic + &#39;.png&#39;&quot; v-bind:alt=&quot;pic&quot;&gt;
    &lt;/div&gt;

However it works perfectly when I just do:

    &lt;img src=&quot;../assets/dog.png&quot; alt=&quot;dog&quot;&gt;

My case is similar to this [fiddle][1], but here it works with img URL, but in mine with actual file paths, it does not work.

What should be correct way to do it?


  [1]: https://jsfiddle.net/9a6Lg2vd/5/

Vue.js dynamic images not working

I have an Object like this that is created by underscore&#39;s `_.groupBy()` method.

    myObject = {
      &quot;key&quot; : [{Object},{Object2},{Object3}],
      &quot;key2&quot; : [{Object4},{Object5},{Object6}],
      ...
    }

How would I define that as an Interface with TypeScript?
i don&#39;t want to simply define it as `myObject:Object = { ... ` but rather have an own type for it.

How to define an interface for objects with dynamic keys?

Visual Studio 2017 (15.x) supports C# 7, but what about Visual Studio *2015* (14.x)?

How can I use C# 7 with it?

How to use C# 7 with Visual Studio 2015?

Visual Studio 2017 (15.x) supports C# 7, but what about Visual Studio 2015 (14.x)?
How can I use C# 7 with it?

When operations were introduced in Roslyn one of the goals was to provide lowered operations (I think it was in design review meeting video) which as far as I understand should provide explicit operations for implicit compiler actions on high level ones. I see Lowering directory in Roslyn, but classes are internal there. It is possible to get lowered operations now or no public API available yet?

In sample below operations already removing some implicit parts - adding return statement for expression body and expose symbol for overloaded operator. But pre and post increments differs only by kind.

    using Microsoft.CodeAnalysis;
    using Microsoft.CodeAnalysis.CSharp;
    using Microsoft.CodeAnalysis.CSharp.Syntax;
    using Microsoft.CodeAnalysis.Semantics;
    using System.Linq;
    
    namespace so39468373
    {
        internal static class Program
        {
            private static void Main()
            {
                var tree = CSharpSyntaxTree.ParseText(@&quot;
    public class c
    {
        public static c operator ++(c o) { return o; }
        static c pre(c o) =&gt; ++o;
        static c post(c o) =&gt; o++;
        public static void Main() {}
    }&quot;);
                var mscorlib = MetadataReference.CreateFromFile(typeof(object).Assembly.Location);
                var compilation = CSharpCompilation.Create(null, new[] { tree }, new[] { mscorlib });
                var model = compilation.GetSemanticModel(tree);
                foreach (var node in tree.GetRoot().DescendantNodes().OfType&lt;ArrowExpressionClauseSyntax&gt;())
                {
                    var operation = model.GetOperation(node);
                    var block = (IBlockStatement)operation;
                    var statement = (IReturnStatement)block.Statements.First();
                    var increment = (IIncrementExpression)statement.ReturnedValue;
                    // How to get lowered operations for increment here?
                }
            }
        }
    }

Code on github - https://github.com/isanych/so-39468373

Lowered operations in roslyn

In C# 6.0 the &quot;when&quot; keyword was introduced, now you&#39;re able to filter an exception in a catch block. But isn&#39;t this the same as a if statement inside a catch block? if so, isn&#39;t it just syntactic sugar or i&#39;m missing something?

For example a try catch block with the &quot;when&quot; keyword:

    try { … } 
    catch (WebException ex) when ex.Status == WebExceptionStatus.Timeout {
       //do something
    }
    catch (WebException ex) when ex.Status== WebExceptionStatus.SendFailure {
       //do something
    }
    catch (Exception caught) {…}

Or

    try { … } 
    catch (WebException ex) {
       if(ex.Status == WebExceptionStatus.Timeout) {
          //do something
       }
    }
    catch (WebException ex) {
       if(ex.Status == WebExceptionStatus.SendFailure) {
          //do something
       }
    }
    catch (Exception caught) {…}

Is the &quot;when&quot; keyword in a try catch block the same as an if statement?

I have a .NET Core 1.0.0 console application and two environments. I need to be able to use `appSettings.dev.json` and `appSettings.test.json` based on environment variables I set at run time. This seems to be quite straight forward for ASP.NET Core web applications, via dependency injection and IHostingEnvironment and the EnvironmentName env. variable, however how should I wire things up for the console application (besides writing my own custom code that uses `Microsoft.Framework.Configuration.EnvironmentVariables`)?  

Thank you. 

.NET Core console application, how to configure appSettings per environment?

I followed the [Safe storage of app secrets during development][1] guide over on the asp.net docs during development but it does not describe how to use it when publishing to another machine for QA, Production, etc.  What I figured it would do was insert them into the appsettings.json during publish but it does not.  I ended up having to place my SendGrid keys and other sensitive information directly into the appsettings.json which really defeats the purpose of the app secrets.

Is using app secrets the best way or is there another way to store API keys and SQL user/passwords in my configs?


  [1]: https://docs.asp.net/en/latest/security/app-secrets.html

How to deploy ASP.NET Core UserSecrets to production

    public interface IBar {
    }
    public class Bar : IBar {
    }
    public class Bar2 : IBar {
    }
    public interface IFoo {
      Task&lt;T&gt; Get&lt;T&gt;(T o) where T : IBar;
    }
    public class Foo : IFoo {
      public async Task&lt;T&gt; Get&lt;T&gt;(T o) where T : IBar {
        ...
      }
    }

I can then call this method using reflection:

    var method = typeof(IFoo).GetMethod(nameof(IFoo.Get));
    var generic = method.MakeGenericMethod(bar2.GetType());
    var task = generic.Invoke(foo, new [] { bar2 });

How do I await on this `Task`? and How do I cast it to `Task&lt;bar2.GetType()&gt;`?



How to call a generic async method using reflection

I&#39;ve met with a strange problem. I had 7 projects in the solution. I had to add another MVC project. Now when the document (from the new project) is opened  (for example `HomeController.cs`) and when this project is initializing at the start, it freezes the whole IDE like this:

[![enter image description here][1]][1]


  [1]: http://i.stack.imgur.com/wuZuH.png

(Some projects do not load)

After that, I have to kill the process. When I open VS again and fast click on another project (which is initializing) the freezing issue is gone. I have no idea what can cause a problem like this. I&#39;ve tried with and without ReSharper but I get the same result. Also, I restored default settings of VS. Also repaired whole VS.

Maybe someone had the same problem and could give some helpful advice?

Visual Studio freezing (crashing) while loading solution

I have installed Visual Studio 2017 RC, and by default it set language to my system language (Polish) so I was trying to change it to EN but in Options &gt; Environment &gt; International Settings i have only Polish language. There is link to &quot;download more languages&quot;, and it redirects to: [https://www.visualstudio.com/downloads/][1]
And there I can only find language packs for VS 15.
Anyone know where I can find EN language pack for VS 17 RC?


  [1]: https://www.visualstudio.com/downloads/

Change language of Visual Studio 2017 RC

I&#39;m trying out the new VS 2017 RC and wondering if anyone knows how to get the previous debugging behavior back

In VS 2015 it went like this:

Press start debugging

- Website opens in new Chrome tab
- Press stop debugging
- Website is still open and the site is still running/active

Now in 2017:

- Press start debugging
- Website opens in new window that can&#39;t dock with any other Chrome windows/tabs
- Press stop debugging
- Website/Chrome window closes, can&#39;t continue using the site unless I manually go to the localhost window in Chrome

Is it possible in 2017 to switch back to the 2015 style? So the Chrome/Website window can dock with other Chrome windows/tabs, and it stays open after you stop debugging?

Additionally, I find the new Chrome window frustrating to use, as it seems not to have any history/content available. E.g I can&#39;t autocomplete forms or urls, which is very annoying when I&#39;m trying to test a form

How to stop browser closing automatically when you stop debugging on VS 2017

I&#39;m using Visual Studio 2017 RC and getting very frustrated with the new Chrome window that pops up when you click Debug.

Issues with the Debug Chrome Window:

- Takes ages to start/&quot;attach&quot; website (I think it&#39;s attaching all the javascript debugging which I don&#39;t need because I use Chrome DevTools for that anyway)
- Not dockable (as a tab) with other Chrome windows
- Doesn&#39;t remember form history. If I&#39;m testing out forms I can&#39;t autocomplete form data, so I have to type the whole lot out every time
- Doesn&#39;t remember url history. If I&#39;m testing a specific page on my site, I can&#39;t quickly select the url from Chrome url bar dropdown. Have to type the url in full
- Extensions aren&#39;t enabled so I can&#39;t use my ruler or color picker extensions
- Chrome window closes when debugging stops so I have to open up a new window to keep browsing the local site

Does anyone know how to disable this new Debug style window and go back to how it was in VS 2015?


How to disable the new debug window in VS2017

I&#39;ve installed Visual Studio 2017 Community that was released a week ago, and I started exploring the new features of C# 7.

So I created a simple method that returns two values:

    public class Program
    {
        public static void Main(string[] args)
        {
            (int sum, int count) a = ReturnTwoValues();
        }
    
        static (int sum, int count) ReturnTwoValues() =&gt; (1, 1);
    }

Compiler is generating an error:

&gt; Error	CS8137	Cannot define a class or member that utilizes tuples
&gt; because the compiler required type
&gt; &#39;System.Runtime.CompilerServices.TupleElementNamesAttribute&#39; cannot be
&gt; found. Are you missing a reference?

I tried finding a reference in the framework with this name, but with no luck !

**If we need additional stuff to use C# 7.0 features, then it is very weird that we need to do that for every project ?!**

Unable to return Tuple from a method using Visual Studio 2017 and C# 7.0

I followed [this article][1] to deploy my ASP.NET MVC Core 1.0 app to local IIS on my Windows 10 that is using IIS 10. The application deployed successfully and it opens the home page fine. I&#39;m using *Individual User Accounts Authentication*. On the home page when I enter login/password and click *Login* button, I get the following error. I&#39;m using the latest versions of ASP.NET Core and VS2015. I used VS2015 Publish wizard to publish the app. Everything is done on the same machine:

&gt; &lt;h2&gt;An error occurred while processing your request.&lt;/h2&gt;
&gt; &lt;h3&gt;Development Mode&lt;/h3&gt;
&gt; Swapping to **Development** environment will display more detailed information about the error that occurred.&lt;br&gt;
**Development environment should not be enabled in deployed applications**, as it can result in sensitive information from exceptions being displayed to end users. For local debugging, development environment can be enabled by setting the **ASPNETCORE_ENVIRONMENT** environment variable to **Development**, and restarting the application.


  [1]: https://weblog.west-wind.com/posts/2016/Jun/06/Publishing-and-Running-ASPNET-Core-Applications-with-IIS

ASP.NET Core deployment to IIS error: Development environment should not be enabled in deployed applications

I need to install Visual C++ Build Tools. When I&#39;ve download installer, I&#39;ve tried to install it, however it&#39;s telling me I need to uninstall VS 2015!

How can I solve it?
Why is Visual C++ Build tools telling me it needs to remove current VS 2015 installation?

How to install Visual C++ Build tools?

I have an ASP.NET core project and I&#39;m getting this error when I try to build it:

    error TS18003: Build:No inputs were found in config file &#39;Z:/Projects/client/ZV/src/ZV/Scripts/tsconfig.json&#39;. Specified &#39;include&#39; paths were &#39;[&quot;**/*&quot;]&#39; and &#39;exclude&#39; paths were &#39;[&quot;../wwwroot/app&quot;,&quot;node_modules/*&quot;]&#39;.
    1&gt;         The command exited with code 1.
    1&gt;       Done executing task &quot;VsTsc&quot; -- FAILED.

This is my `tsconfig.json` file:

    {
      &quot;compileOnSave&quot;: true,
      &quot;compilerOptions&quot;: {
        &quot;emitDecoratorMetadata&quot;: true,
        &quot;experimentalDecorators&quot;: true,
        &quot;lib&quot;: [ &quot;es5&quot;, &quot;dom&quot; ],
        &quot;module&quot;: &quot;commonjs&quot;,
        &quot;moduleResolution&quot;: &quot;node&quot;,
        &quot;noEmitOnError&quot;: true,
        &quot;noImplicitAny&quot;: false,
        &quot;outDir&quot;: &quot;../wwwroot/app/&quot;,
        &quot;removeComments&quot;: false,
        &quot;sourceMap&quot;: true,
        &quot;target&quot;: &quot;es6&quot;
      },
      &quot;exclude&quot;: [
        &quot;../wwwroot/app&quot;,
        &quot;node_modules/*&quot;
      ]
    }

Is this a bug or am I doing something wrong? I did recently upgrade Visual Studio 2015 to update 3. Has anyone encountered this before?


    



tsconfig.json: Build:No inputs were found in config file

I cloned the [ASP.NET Core SignalR Repo][1] locally, and try opening the solution from within the following environment.

**IDE**

    Microsoft Visual Studio Enterprise 2015
    Version 14.0.25431.01 Update 3
    Microsoft .NET Framework
    Version 4.6.01055

**DOT NET CLI**

    λ dotnet --info
    .NET Command Line Tools (1.0.0-preview2-1-003177)
    
    Product Information:
     Version:            1.0.0-preview2-1-003177
     Commit SHA-1 hash:  a2df9c2576
    
    Runtime Environment:
     OS Name:     Windows
     OS Version:  6.1.7601
     OS Platform: Windows
     RID:         win7-x64

I end up seeing a lot of these kinds of error messages:

&gt; `..\Repos\SignalR\src\Microsoft.AspNetCore.SignalR\Microsoft.AspNetCore.SignalR.csproj`
&gt; : error  : The default XML namespace of the project must be the
&gt; MSBuild XML namespace. If the project is authored in the MSBuild 2003
&gt; format, please add
&gt; `xmlns=&quot;http://schemas.microsoft.com/developer/msbuild/2003&quot;` to the
&gt; &lt;Project&gt; element. If the project has been authored in the old 1.0 or
&gt; 1.2 format, please convert it to MSBuild 2003 format.  `..\Repos\SignalR\src\Microsoft.AspNetCore.SignalR\Microsoft.AspNetCore.SignalR.csproj`

I want to know how to fix this the correct way.


  [1]: https://github.com/aspnet/SignalR

The default XML namespace of the project must be the MSBuild XML namespace

In C# 7, we can use

    if (x is null) return;

instead of

    if (x == null) return;

Are there any advantages to using the new way (former example) over the old way?

Are the semantics any different?

Is it just a matter of taste? If not, when should I use one over the other?

Reference: [What’s New in C# 7.0][1].


[1]: https://devblogs.microsoft.com/dotnet/whats-new-in-csharp-7-0/

What is the difference between &quot;x is null&quot; and &quot;x == null&quot;?

I am looking at the new implementations in [**C# 7.0**][1] and I find it interesting that they have implemented local functions but I cannot imagine a scenario where a local function would be preferred over a lambda expression, and what is the difference between the two.

I do understand that lambdas are `anonymous` functions meanwhile local functions are not, but I can&#39;t figure out a real world scenario, where local function has advantages over lambda expressions 

Any example would be much appreciated. Thanks.




  [1]: https://blogs.msdn.microsoft.com/dotnet/2016/08/24/whats-new-in-csharp-7-0/

Local function vs Lambda C# 7.0

I decompiled some C# 7 libraries and saw `ValueTuple` generics being used. What are `ValueTuples` and why not `Tuple` instead?

* https://docs.microsoft.com/en-gb/dotnet/api/system.tuple
* https://docs.microsoft.com/en-gb/dotnet/api/system.valuetuple

What&#39;s the difference between System.ValueTuple and System.Tuple?

I&#39;ve been getting a message in Visual Studio 2017, specifically, `IDE0018 Variable declaration can be inlined.`

So I try using an inline variable declaration the way it&#39;s mentioned in the visual studio 2017 release notes, but I can&#39;t get my project to compile.  

It show no error messages, but the output shows &quot;`Rebuild All failed.....  error CS1525: Invalid expression term &#39;int&#39;`&quot;  

The error only shows up in the output, not as an actual error in the error list.

Here is an actual example of the code I&#39;m using that is failing.

    if (int.TryParse(ExpYear, out int IExpYear))
      {
        if (IExpYear &lt; DateTime.Now.Year || IExpYear &gt; DateTime.Now.AddYears(10).Year)
        {
          e += &quot;Expiration Year is invalid.\n&quot;;
        }
      }
      else
      {
        e += &quot;Expiration Year is not a number.\n&quot;;
      }

If I revert the change, it compiles as expected.  Is it possible that I&#39;m not using the c#7 compiler somehow?

Thank you.


Update: I found the language setting in Build &gt; Advanced and set it to C# 7.0.  Building the project now gives me this error:

&gt;CSC : error CS1617: Invalid option &#39;7&#39; for /langversion; must be ISO-1, ISO-2, Default or an integer in range 1 to 6.

Content Type	Original Author	Original Content on Stackoverflow
Question	Luis Teijon	View Question on Stackoverflow
Solution 1 - C#	Stephen Kennedy	View Answer on Stackoverflow
Solution 2 - C#	yibe	View Answer on Stackoverflow

How to use C# 7 with Visual Studio 2015?

C# Problem Overview

C# Solutions

Solution 1 - C#

Solution 2 - C#

How to define an interface for objects with dynamic keys?

Vue.js dynamic images not working

Attributions