The NuGet package [Microsoft.AspNet.WebApi.Owin](https://www.nuget.org/packages/Microsoft.AspNet.WebApi.Owin) contains that DLL.

You can install it by right-clicking on the References folder of your project and selecting &quot;Manage NuGet Packages...&quot; and searching for &quot;Microsoft.AspNet.WebApi.Owin&quot;. Or you can use the Package Manager Console and type the following:

    Install-Package Microsoft.AspNet.WebApi.Owin

If you use the Package Manager Console within Visual Studio, be sure you have the intended project selected in the drop down labeled &quot;Default project:&quot; That is easy to overlook.

I was reading the Bootstrap documentation about the button tags (http://getbootstrap.com/css/#buttons-tags), as `&lt;button&gt;` and `&lt;a&gt;` tags have exactly the same appearance, and I found this :

&gt; **Cross-browser rendering**
&gt; 
&gt; As a best practice, we highly recommend using the `&lt;button&gt;` element
&gt; whenever possible to ensure matching cross-browser rendering.

What is the reason that can lead me to use a `&lt;button&gt;` tag (which doesn&#39;t have a href attribute) instead of a `&lt;a&gt;` for navigation ?

Maybe `&lt;button&gt;` is better when designing web applications when it interacts with the page itself, and of course for submitting forms, but is it all ?

[this question is related to https://stackoverflow.com/questions/19201420/seo-button-vs-a-html-tags but the question is not the same]

When should I use a button (&lt;button&gt;) or a link (&lt;a&gt;) in HTML?

I am trying to use Reactjs with a kendo splitter. The splitter has a style attribute like

    style=&quot;height: 100%&quot;

With Reactjs, if I have understood things correctly, this can be implemented using an inline style

    var style = {
      height: 100
    }

However, I am also using Dustin Getz [jsxutil][1] to in an attempt to split things a part a bit more and have independent html fragments. Thus far I have the following html fragment (splitter.html)

    &lt;div id=&quot;splitter&quot; className=&quot;k-content&quot;&gt;
      &lt;div id=&quot;vertical&quot;&gt;
        &lt;div&gt;
          &lt;p&gt;Outer splitter : top pane (resizable and collapsible)&lt;/p&gt;
        &lt;/div&gt;
        &lt;div id=&quot;middlePane&quot;&gt;
       	  {height}
          &lt;div id=&quot;horizontal&quot; style={height}&gt;
            &lt;div&gt;
              &lt;p&gt;Inner splitter :: left pane&lt;/p&gt;
            &lt;/div&gt;
            &lt;div&gt;
              &lt;p&gt;Inner splitter :: center pane&lt;/p&gt;
            &lt;/div&gt;
            &lt;div&gt;
              &lt;p&gt;Inner splitter :: right pane&lt;/p&gt;
            &lt;/div&gt;
          &lt;/div&gt;
        &lt;/div&gt;
      &lt;div&gt;
      &lt;p&gt;Outer splitter : bottom pane (non-resizable, non-collapsible)&lt;/p&gt;
    &lt;/div&gt;
  &lt;/div&gt;
&lt;/div&gt;

and a splitter.js component which references this html as follows

    define([&#39;react&#39;, &#39;external/react/js/jsxutil&#39;,&#39;text!internal/html/splitter.html&#39;],
      function(React, jsxutil, splitterHtml) {
        &#39;use strict&#39;;
        console.log(&#39;in app:&#39; + splitterHtml);
        return React.createClass({

          render: function () {
            var scope = {
              height: 100
            };
            console.log(&#39;about to render:&#39; + scope.height);

            var dom = jsxutil.exec(splitterHtml, scope);
            console.log(&#39;rendered:&#39; + dom);
            return dom;
          }    
        });
      }
    )

Now when I run this, I can see the height correctly if I put it as content. However, when it executes as the style properties I am getting an error

    The `style` prop expects a mapping from style properties to values, not a string. 

So I obviously haven&#39;t quite got it mapped across correctly.

I&#39;d be really grateful if someone could give me a steer on correcting this. 

  [1]: https://github.com/dustingetz/react-dynamic-form-kendo/tree/master/webapp

Reactjs - setting inline styles correctly

I had a version number problem with system.web.http.owin.

So I removed it from my projects package references, with the idea that I would re-added it to see if it fixed the problem. However it has disappeared completely. I.e. in visual studio if I go: 

solution explorer &gt; myProject &gt; references &gt; RMC &gt; add reference &gt; 

and then search for `system.web.http.owin` it doesn&#39;t appear.

Any ideas what has gone wrong or what package I need to install to make it re-appear.



My original error message...

&gt; Error	7	Assembly &#39;System.Web.Http.Owin, Version=5.1.0.0,
&gt; Culture=neutral, PublicKeyToken=31bf3856ad364e35&#39; uses
&gt; &#39;System.Web.Http, Version=5.1.0.0, Culture=neutral,
&gt; PublicKeyToken=31bf3856ad364e35&#39; which has a higher version than
&gt; referenced assembly &#39;System.Web.Http, Version=4.0.0.0,
&gt; Culture=neutral,
&gt; PublicKeyToken=31bf3856ad364e35&#39;	e:\user\project1\src\packages\Microsoft.AspNet.WebApi.Owin.5.1.1\lib\net45\System.Web.Http.Owin.dll	Smots.Core



How do I get System.Web.Http.Owin?

I had a version number problem with system.web.http.owin.
So I removed it from my projects package references, with the idea that I would re-added it to see if it fixed the problem. However it has disappeared completely. I.e. in visual studio if I go:
solution explorer > myProject > references > RMC > add reference >
and then search for <code>system.web.http.owin</code> it doesn't appear.
Any ideas what has gone wrong or what package I need to install to make it re-appear.
My original error message...
> Error	7	Assembly 'System.Web.Http.Owin, Version=5.1.0.0,
> Culture=neutral, PublicKeyToken=31bf3856ad364e35' uses
> 'System.Web.Http, Version=5.1.0.0, Culture=neutral,
> PublicKeyToken=31bf3856ad364e35' which has a higher version than
> referenced assembly 'System.Web.Http, Version=4.0.0.0,
> Culture=neutral,
> PublicKeyToken=31bf3856ad364e35'	e:\user\project1\src\packages\Microsoft.AspNet.WebApi.Owin.5.1.1\lib\net45\System.Web.Http.Owin.dll	Smots.Core

When planning out my programs, I often start with a chain of thought like so:

&gt; A football team is just a list of football players. Therefore, I should represent it with:

&gt;     var football_team = new List&lt;FootballPlayer&gt;();

&gt;The ordering of this list represent the order in which the players are listed in the roster.

But I realize later that teams also have other properties, besides the mere list of players, that must be recorded. For example, the running total of scores this season, the current budget, the uniform colors, a `string` representing the name of the team, etc..

So then I think:

&gt; Okay, a football team is just like a list of players, but additionally, it has a name (a `string`) and a running total of scores (an `int`). .NET does not provide a class for storing football teams, so I will make my own class. The most similar and relevant existing structure is `List&lt;FootballPlayer&gt;`, so I will inherit from it:

&gt;     class FootballTeam : List&lt;FootballPlayer&gt; 
    { 
        public string TeamName; 
        public int RunningTotal 
    }

But it turns out that [a guideline says you shouldn&#39;t inherit from `List&lt;T&gt;`][1]. I&#39;m thoroughly confused by this guideline in two respects.

Why not?
--------

Apparently [`List` is somehow optimized for performance][2]. How so? What performance problems will I cause if I extend `List`? What exactly will break?

Another reason I&#39;ve seen is that `List` is provided by Microsoft, and I have no control over it, so [I cannot change it later, after exposing a &quot;public API&quot;][3]. But I struggle to understand this. What is a public API and why should I care? If my current project does not and is not likely to ever have this public API, can I safely ignore this guideline? If I do inherit from `List` *and* it turns out I need a public API, what difficulties will I have?

Why does it even matter? A list is a list. What could possibly change? What could I possibly want to change?

And lastly, if Microsoft did not want me to inherit from `List`, why didn&#39;t they make the class `sealed`?

What else am I supposed to use?
-------------------------------

Apparently, for custom collections, Microsoft has provided a `Collection` class which should be extended instead of `List`. But this class is very bare, and does not have many useful things, [such as `AddRange`][4], for instance. [jvitor83&#39;s answer][5] provides a performance rationale for that particular method, but how is a slow `AddRange` not better than no `AddRange`?

Inheriting from `Collection` is way more work than inheriting from `List`, and I see no benefit. Surely Microsoft wouldn&#39;t tell me to do extra work for no reason, so I can&#39;t help feeling like I am somehow misunderstanding something, and inheriting `Collection` is actually not the right solution for my problem.

I&#39;ve seen suggestions such as implementing `IList`. Just no. This is dozens of lines of boilerplate code which gains me nothing.

Lastly, some suggest wrapping the `List` in something: 

    class FootballTeam 
    { 
        public List&lt;FootballPlayer&gt; Players; 
    }

There are two problems with this:

1. It makes my code needlessly verbose. I must now call `my_team.Players.Count` instead of just `my_team.Count`. Thankfully, with C# I can define indexers to make indexing transparent, and forward all the methods of the internal `List`... But that&#39;s a lot of code! What do I get for all that work?

2. It just plain doesn&#39;t make any sense. A football team doesn&#39;t &quot;have&quot; a list of players. It *is* the list of players. You don&#39;t say &quot;John McFootballer has joined SomeTeam&#39;s players&quot;. You say &quot;John has joined SomeTeam&quot;. You don&#39;t add a letter to &quot;a string&#39;s characters&quot;, you add a letter to a string. You don&#39;t add a book to a library&#39;s books, you add a book to a library.

I realize that what happens &quot;under the hood&quot; can be said to be &quot;adding X to Y&#39;s internal list&quot;, but this seems like a very counter-intuitive way of thinking about the world.

## My question (summarized) ##

What is the correct C# way of representing a data structure, which, &quot;logically&quot; (that is to say, &quot;to the human mind&quot;) is just a `list` of `things` with a few bells and whistles?

Is inheriting from `List&lt;T&gt;` always unacceptable? When is it acceptable? Why/why not? What must a programmer consider, when deciding whether to inherit from `List&lt;T&gt;` or not?

  [1]: https://stackoverflow.com/a/5376343/1042555
  [2]: https://stackoverflow.com/a/5376358/1042555
  [3]: https://stackoverflow.com/questions/5376203/inherit-listt#comment6077237_5376343
  [4]: https://stackoverflow.com/questions/1474863/addrange-to-a-collection
  [5]: https://stackoverflow.com/a/12039943/1042555

Why not inherit from List&lt;T&gt;?

Ok, I have an old batch file that does exactly what I need.  However, with out new administration we can&#39;t run the batch file anymore so I need to start up with C#.

I&#39;m using Visual Studio C# and already have the forms set up for the application I need to build. (I&#39;m learning as I go)

Here is what I need to accomplish in C# (This is the batch guts)

    sqlcmd.exe -S .\PDATA_SQLEXPRESS -U sa -P 2BeChanged! -d PDATA_SQLEXPRESS  -s ; -W -w 100 -Q &quot;SELECT tPatCulIntPatIDPk, tPatSFirstname, tPatSName, tPatDBirthday  FROM  [dbo].[TPatientRaw] WHERE tPatSName = &#39;%name%&#39; &quot;

Basically it uses `SQLCMD.exe` with the already existing datasource called `PDATA_SQLExpress`.  
I&#39;ve searched and gotten close but I&#39;m still at a loss on where to start. 


How to directly execute SQL query in C#?

I have a cursor file in project. I have given the absolute path in code i.e  
  

    F:/r.cur  

 the problem is this is hard-coded path And i Want relative path so that if i move my solution to another system the code should not effect.

please suggest how to set relative path
  
  
    //current code i am using 
     p.Cursor = new Cursor(&quot;F:/r.cur&quot;);
  


How to get current working directory path c#?

After FxCop 10 Microsoft stopped shipping a separate installer for FxCop.
Officially one can currently only run code analysis (FxCop 12.0 / 14.0 / 15.0) after installing Visual Studio 2013 / 2015 / 2017.
However, we are adamant about not installing Visual Studio on the build agents (the installation needs then to be kept in-sync with what we have got on the developer computers etc.).

So how would i go about getting FxCop 12.0 / 14.0 / 15.0 to work on a build agent, preferrably without installing anything else? I would accept adding a few binaries and msbuild files to source control, though.
Otherwise: Is there a way to only install the FxCop stuff using Visual Studio 2013 / 2015 / 2017 installer?

Note: we are using Teamcity as build server.

## Answers ##
As there are multiple valid answers for specific environments and FxCop versions, I&#39;ve taken the liberty of linking them here for easier access:

 - [FxCop 15.0 (Visual Studio 2017)](https://stackoverflow.com/a/49115418/684096)
 - [FxCop 14.0 (Visual Studio 2015)](https://stackoverflow.com/a/21731245/684096)
 - [FxCop 12.0 (Visual Studio 2013)](https://stackoverflow.com/a/32093939/684096)
 - [SonarQube](https://stackoverflow.com/a/37720315/684096)

Running Code Analysis (FxCop &gt; 10) on build agent without installing Visual Studio

I&#39;m struggling to find a modern example of some asynchronous C# code that uses RestSharp with `async` and `await`. I know there&#39;s [been a recent update by Haack][1] but I don&#39;t know how to use the new methods.

Also, how can I provide a cancellation token so that the operation can be canceled (say, if a person is sick of waiting and presses the Cancel button in the app&#39;s UI).

  [1]: http://haacked.com/archive/2013/09/18/restsharp-104-2-0-released.aspx/

How to use RestSharp with async/await

I have copied a previous project and renamed it. Once I had successfully renamed all the name spaces and it build correctly. I got the following error when I ran the application:

    The following errors occurred while attempting to load the app.
    - The OwinStartup attribute discovered in assembly &#39;User Manager Interface&#39; referencing    startup type &#39;User_Manager_Interface.Startup&#39; conflicts with the attribute in assembly   &#39;Service Monitor Web Interface&#39; referencing startup type  &#39;Service_Monitor_Web_Interface.Startup&#39; because they have the same FriendlyName &#39;&#39;. Remove or   rename one of the attributes, or reference the desired type directly.
    To disable OWIN startup discovery, add the appSetting owin:AutomaticAppStartup with a value of &quot;false&quot; in your web.config.
    To specify the OWIN startup Assembly, Class, or Method, add the appSetting owin:AppStartup with the fully qualified startup class or configuration method name in your web.config.


I have figured out that if I comment out the first line below then the error goes away.

    //[assembly: OwinStartupAttribute(typeof(Service_Monitor_Web_Interface.Startup))]
    namespace Service_Monitor_Web_Interface
    {
    public partial class Startup
    {
        public void Configuration(IAppBuilder app)
        {
            ConfigureAuth(app);
        }
    }
    }


I renamed my solution from User_Manager_Interface to Service_Monitor_Web_Interface.

I cant seem to find any places with the old name, howevel in the error it mentions it.

Error renaming ASP.NET MVC project

I am working on an Asp.Net MVC 4 Application in which I am using SignalR 2.0.1 and I Mapped it using Owin Startup class and it worked fine at first.

All of a sudden when I tried to rebuild my app it said that the type are namespace `IAppbuilder` could not be found.

Following is my start up class

    using Microsoft.Owin;
    using Owin;
    using WhiteBoardApp;
    
    namespace WhiteBoardApp
    {
        public class Startup
        {
            public void Configuration(IAppBuilder app)
            {
                app.MapSignalR();
            }
        }
    }


I have installed `Owin` package too, and for some reasons I could not find Owin Startup class so I just added a normal class and included all the references that are needed. 
May I know where I am making a mistake

The type or namespace IAppBuilder could not be found(missing using a directive pr an assembly reference)

This is driving me insane. 

I&#39;m using latest signalR release (2.0.2). This is my hub code (OnConnected)

            public override Task OnConnected()
            {
                //User is null then Identity and Name too.
                Connections.Add(Context.User.Identity.Name, Context.ConnectionId);
                return base.OnConnected();
            }

And this is my Controller&#39;s login method:

   

            [HttpPost]
            [AllowAnonymous]
            [ValidateAntiForgeryToken]
            public async Task&lt;ActionResult&gt; Login(LoginViewModel model, string returnUrl)
            {
                if (ModelState.IsValid)
                {
                  var user = await UnitOfWork.UserRepository.FindAsync(model.UserName,  model.Password);
                    
                    if (user != null)
                    {
                        await SignInAsync(user, model.RememberMe);
    
                        return RedirectToLocal(returnUrl);
                    }
                }
    
                TempData[&quot;ErrorMessage&quot;] = Resources.InvalidUserNameOrPassword;
    
                // If we got this far, something failed, redisplay form
                return RedirectToAction(&quot;Index&quot;,&quot;Home&quot;);
            }


I found that some people are having this issue on OnDisconnected, I don&#39;t even make it there.

I&#39;m using MCV5 template.

Do you have any idea what is wrong?


Context.User.Identity.Name is null with SignalR 2.X.X. How to fix it?

**Update 2017!**

The issue I had when I posted the original question has got nothing to do with the recent changes Facebook made when they forced everyone to version 2.3 of their API.  For a solution to that specific problem, see **sammy34&#39;s answer below**.  Version 2.3 of the /oauth/access_token endpoint now returns JSON instead of form-encoded values

**For historical reasons, here&#39;s my original question/issue:**

I&#39;ve got an MVC5 Web application which is using the built-in support for authentication via Facebook and Google.  When we built this app a few months ago, we followed this tutorial: http://www.asp.net/mvc/tutorials/mvc-5/create-an-aspnet-mvc-5-app-with-facebook-and-google-oauth2-and-openid-sign-on and everything worked great.

Now, all of a sudden, the Facebook authentication has just stopped working alltogether.  The Google authentication still works great.

Description of the problem: We click the link to connect using Facebook, we are redirected to Facebook where we are prompted if we wan&#39;t to allow our Facebook app access to our profile.  When we click &quot;OK&quot; we are redirected back to our site, but instead of being logged in we simply end up at the login screen.

I&#39;ve gone through this process in debug mode and I&#39;ve got this ActionResult in my account controller as per the tutorial mentioned above:

    // GET: /Account/ExternalLoginCallback
    [AllowAnonymous]
    public async Task&lt;ActionResult&gt; ExternalLoginCallback(string returnUrl)
    {
        var loginInfo = await AuthenticationManager.GetExternalLoginInfoAsync();
        if (loginInfo == null)
        {
            return RedirectToAction(&quot;Login&quot;);
        }
        ............

When stepping through the code and upon returning from Facebook, the loginInfo object is always NULL, which causes the user to be redirected back to the login.

In order to understand what is actually happening behind the scenes, I installed Fiddler and monitored the HTTP traffic.  What I disovered is that upon clicking &quot;OK&quot; at the Facebook permission dialog, Facebook redirects back to our application with this URL:

    https://localhost/signin-facebook?code=&lt;access-token&gt;

This URL is not an actual file and probably handled by some controller/handler built into this OWIN framework I&#39;m guessing.  Most likely, it is connecting back to Facebook using the given code to query information about the user which is trying to login.  Now, the problem is that instead of doing that, we are redirected to:

    /Account/ExternalLoginCallback?error=access_denied

Which I&#39;m sure is something Facebook is doing, that is, instead of giving us the user data, it&#39;s redirecting us back with this error message.

This causes the `AuthenticationManager.GetExternalLoginInfoAsync();` to fail and always return NULL.

I&#39;m completely out of ideas.  As far as we know, we did not change anything on our end.

I&#39;ve tried creating a new Facebook app, I&#39;ve tried following the tutorial again but I always have the same problem.

Any ideas welcome!

**Update!**

OK, this is driving me insane!  I&#39;ve now manually gone through the steps required to perform the authentication and everything works great when I do that.  Why on earth is this not working when using the MVC5 Owin stuff?

This is what I did:

        // Step 1 - Pasted this into a browser, this returns a code
        https://www.facebook.com/dialog/oauth?response_type=code&amp;client_id=619359858118523&amp;redirect_uri=https%3A%2F%2Flocalhost%2Fsignin-facebook&amp;scope=&amp;state=u9R1m4iRI6Td4yACEgO99ETQw9NAos06bZWilJxJrXRn1rh4KEQhfuEVAq52UPnUif-lEHgayyWrsrdlW6t3ghLD8iFGX5S2iUBHotyTqCCQ9lx2Nl091pHPIw1N0JV23sc4wYfOs2YU5smyw9MGhcEuinvTAEql2QhBowR62FfU6PY4lA6m8pD3odI5MwBYOMor3eMLu2qnpEk0GekbtTVWgQnKnH6t1UcC6KcNXYY
    
    I was redirected back to localhost (which I had shut down at this point to avoid being redirected immediately away).  The URL I was redirected to is this:
    
    https://localhost/signin-facebook?code=&lt;code-received-removed-for-obvious-reasons&gt;
    
    Now, I grabbed the code I got and used it in the URL below:
    
    // Step 2 - opened this URL in a browser, and successfully retrieved an access token
    https://graph.facebook.com/oauth/access_token?client_id=619359858118523&amp;redirect_uri=https://localhost/signin-facebook&amp;client_secret=&lt;client-secret&gt;&amp;code=&lt;code-from-step-1&gt;
    
    // Step 3 - Now I&#39;m able to query the facebook graph using the access token from step 2!
    
    https://graph.facebook.com/me?access_token=&lt;access-token-from-step-2&gt;


No errors, everything works great!  Then why the hell is this not working when using the MVC5 Owin stuff?  There&#39;s obviously something wrong with the OWin implementation.

ASP.NET MVC5 OWIN Facebook authentication suddenly not working

I have been searching for an hour trying to figure out why this isn&#39;t working.

I have a ASP.Net MVC 5 application with a WebAPI.  I am trying to get Request.GetOwinContext().Authentication, however I can&#39;t seem to find how to include GetOwinContext.  Here is my code:

    using System;
    using System.Collections.Generic;
    using System.Linq;
    using System.Net;
    using System.Net.Http;
    using System.Web;
    using System.Web.Mvc;
    using System.Web.Security;
    using TaskPro.Models;

    namespace TaskPro.Controllers.api
    {
        public class AccountController : ApiController
        {
            [HttpPost]
            [AllowAnonymous]
            public ReturnStatus Login(LoginViewModel model)
            { 
                if (ModelState.IsValid)
                {
                    var ctx = Request.GetOwinContext(); // &lt;-- Can&#39;t find this

                    return ReturnStatus.ReturnStatusSuccess();
                }

                return base.ReturnStatusErrorsFromModelState(ModelState);
            }
        }
    }

From what I&#39;ve read, it should be part of the System.Net.Http, but I&#39;ve included that and it still isn&#39;t resolving.  Ctrl-Space doesn&#39;t give me any intellisense options either.

What am I missing here?


Content Type	Original Author	Original Content on Stackoverflow
Question	spiderplant0	View Question on Stackoverflow
Solution 1 - .Net	Wallace Kelly	View Answer on Stackoverflow

How do I get System.Web.Http.Owin?

.Net Problem Overview

.Net Solutions

Solution 1 - .Net

Reactjs - setting inline styles correctly

When should I use a button (<button>) or a link (<a>) in HTML?

Attributions