If you look at the [documentation of StringBuilder](https://msdn.microsoft.com/en-us/library/system.text.stringbuilder(v=vs.110).aspx) it has only 4 properties. One of them is `Length`.

&gt; The length of a StringBuilder object is defined by its number of Char objects.

You can use the [Length](https://msdn.microsoft.com/en-us/library/system.text.stringbuilder.length(v=vs.110).aspx) property:

&gt; Gets or sets the length of the current StringBuilder object.


    StringBuilder sb = new StringBuilder();

    if (sb.Length != 0)
    {
        // you have found some difference
    }

Another possibility would be to treat it as a string by using the [String.IsNullOrEmpty](https://msdn.microsoft.com/en-us/library/system.string.isnullorempty(v=vs.110).aspx) method and condense the builder to a string using the `ToString` method. You can even grab the resulting string and assign it to a variable which you would use if you have found some differences:

	string difference = &quot;&quot;;	
	
	if (!String.IsNullOrEmpty(difference = sb.ToString()))
	{
		Console.WriteLine(difference);		
	}





use the `StringBuilder.Length` Property, here the [doc][1]

 
    if (mySB.Length &gt; 0)
    {
         Console.WriteLine(&quot;Bang! is not empty!&quot;); 
    }

  [1]: https://msdn.microsoft.com/en-us/library/system.text.stringbuilder.length(v=vs.110).aspx

Use this, it will work:

    StringBuilder stringbuilder = new StringBuilder();
    if(string.isnullorempty(Convert.toString(stringbuilder)))




Hi I am studying laravel.
I use Eloquent ORM delete method but I get a different result.Not true or false but null.
I set an resource route and there is a destroy method in UsersController.

    public function destroy($id){
    
      $res=User::find($id)-&gt;delete();
      if ($res){
        $data=[
        &#39;status&#39;=&gt;&#39;1&#39;,
        &#39;msg&#39;=&gt;&#39;success&#39;
      ];
      }else{
        $data=[
        &#39;status&#39;=&gt;&#39;0&#39;,
        &#39;msg&#39;=&gt;&#39;fail&#39;
      ];
      return response()-&gt;json($data);
But I always get a response {&quot;status&quot;:&quot;0&quot;,&quot;msg&quot;:&quot;failed&quot;},the record in the database is deleted.

Then I use dd($res) .It shows null in the page.

But from the course I learn it returns a boolean value true or false.

Is there any error in my code?

Can you tell me some other method that I can get a boolean result when I delete data from database?

laravel Eloquent ORM delete() method

What is the preferred way to achieve a nested ListView, or in other words, ListView Widgets that could be included within a scrollable parent?

Imagine a &quot;Reports&quot; page, where a section is an itemized list.

How to implement Nested ListView in Flutter?

I want to test if the `StringBuilder` is empty but there is no `IsEmpty` method or property.

How does one determine this?

How to check if a StringBuilder is empty?

<p>I want to test if the <code>StringBuilder</code> is empty but there is no <code>IsEmpty</code> method or property.</p>
<p>How does one determine this?</p>


I have a .NET Core xUnit project.  I&#39;m trying to call a WCF service from it but get the following exception:

&lt;!-- language: lang-none --&gt;

    System.InvalidOperationException occurred
      HResult=0x80131509
      Message=An error occurred while loading attribute &#39;ServiceContractAttribute&#39; on type &#39;IMyContract&#39;.  Please see InnerException for more details.
    
    Inner Exception 1:
    FileNotFoundException: Could not load file or assembly &#39;System.ServiceModel, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089&#39;. The system cannot find the file specified.

It works with a Framework 4.7 project with the same Nuget Package `System.ServiceModel.Http.4.3.0`.

System.ServiceModel not found in .NET Core project

I&#39;ve been on quite an adventure to get JWT working on DotNet core 2.0 (now reaching final release today).  There is a *ton* of documentation, but all the sample code seems to be using deprecated APIs and coming in fresh to Core, It&#39;s positively dizzying to figure out how exactly it&#39;s supposed to be implemented. I tried using Jose, but app. UseJwtBearerAuthentication has been deprecated, and there is no documentation on what to do next.

Does anyone have an open source project that uses dotnet core 2.0 that can simply parse a JWT from the authorization header and allow me to authorize requests for a HS256 encoded JWT token?

The class below doesn&#39;t throw any exceptions, but no requests are authorized, and I get no indication _why_ they are unauthorized.  The responses are empty 401&#39;s, so to me that indicates there was no exception, but that the secret isn&#39;t matching.

One odd thing is that my tokens are encrypted with the HS256 algorithm, but I see no indicator to tell it to force it to use that algorithm anywhere.

Here is the class I have so far:

	using System;
	using System.Collections.Generic;
	using System.IO;
	using Microsoft.AspNetCore.Authentication;
	using Microsoft.AspNetCore.Authentication.JwtBearer;
	using Microsoft.AspNetCore.Builder;
	using Microsoft.AspNetCore.Hosting;
	using Microsoft.AspNetCore.Http;
	using Microsoft.Extensions.Configuration;
	using Microsoft.Extensions.DependencyInjection;
	using Microsoft.Net.Http.Headers;
	using Newtonsoft.Json.Linq;
	using Microsoft.IdentityModel.Tokens;
	using System.Text;

	namespace Site.Authorization
	{
		public static class SiteAuthorizationExtensions
		{
			public static IServiceCollection AddSiteAuthorization(this IServiceCollection services)
			{
				var signingKey = new SymmetricSecurityKey(Encoding.ASCII.GetBytes(&quot;SECRET_KEY&quot;));

				var tokenValidationParameters = new TokenValidationParameters
				{
					// The signing key must match!
					ValidateIssuerSigningKey = true,
					ValidateAudience = false,
					ValidateIssuer = false,
					IssuerSigningKeys = new List&lt;SecurityKey&gt;{ signingKey },


					// Validate the token expiry
					ValidateLifetime = true,
				};

				services.AddAuthentication(options =&gt;
				{
					options.DefaultAuthenticateScheme = JwtBearerDefaults.AuthenticationScheme;
					options.DefaultChallengeScheme = JwtBearerDefaults.AuthenticationScheme;


				})
				
				.AddJwtBearer(o =&gt;
				{
					o.IncludeErrorDetails = true;
					o.TokenValidationParameters  = tokenValidationParameters;
					o.Events = new JwtBearerEvents()
					{
						OnAuthenticationFailed = c =&gt;
						{
							c.NoResult();

							c.Response.StatusCode = 401;
							c.Response.ContentType = &quot;text/plain&quot;;

							return c.Response.WriteAsync(c.Exception.ToString());
						}

					};
				});

				return services;
			}
		}
	}

JWT on .NET Core 2.0

I&#39;m trying to migrate my auth stuff to Core 2.0 and having an issue using my own authentication scheme. My service setup in startup looks like this:

    var authenticationBuilder = services.AddAuthentication(options =&gt;
    {
    	options.AddScheme(&quot;myauth&quot;, builder =&gt;
    	{
    		builder.HandlerType = typeof(CookieAuthenticationHandler);
    	});
    })
    	.AddCookie();

My login code in the controller looks like this:

    var claims = new List&lt;Claim&gt;
    {
    	new Claim(ClaimTypes.Name, user.Name)
    };
    
    var props = new AuthenticationProperties
    {
    	IsPersistent = persistCookie,
    	ExpiresUtc = DateTime.UtcNow.AddYears(1)
    };
    
    var id = new ClaimsIdentity(claims);
    await HttpContext.SignInAsync(&quot;myauth&quot;, new ClaimsPrincipal(id), props);

But when I&#39;m in a controller or action filter, I only have one identity, and it&#39;s not an authenticated one:

    var identity = context.HttpContext.User.Identities.SingleOrDefault(x =&gt; x.AuthenticationType == &quot;myauth&quot;);

Navigating these changes has been difficult, but I&#39;m guessing that I&#39;m doing .AddScheme wrong. Any suggestions?

EDIT: Here&#39;s (essentially) a clean app that results not in two sets of Identities on User.Identies:

    namespace WebApplication1.Controllers
    {
        public class Testy : Controller
        {
    	    public IActionResult Index()
    	    {
    		    var i = HttpContext.User.Identities;
    		    return Content(&quot;index&quot;);
    	    }
    
    	    public async Task&lt;IActionResult&gt; In1()
    	    {
    			var claims = new List&lt;Claim&gt; { new Claim(ClaimTypes.Name, &quot;In1 name&quot;) };
    		    var props = new AuthenticationProperties  { IsPersistent = true, ExpiresUtc = DateTime.UtcNow.AddYears(1) };
    		    var id = new ClaimsIdentity(claims);
    		    await HttpContext.SignInAsync(CookieAuthenticationDefaults.AuthenticationScheme, new ClaimsPrincipal(id), props);
    		    return Content(&quot;In1&quot;);
    		}
    
    	    public async Task&lt;IActionResult&gt; In2()
    	    {
    		    var claims = new List&lt;Claim&gt; { new Claim(ClaimTypes.Name, &quot;a2 name&quot;) };
    		    var props = new AuthenticationProperties { IsPersistent = true, ExpiresUtc = DateTime.UtcNow.AddYears(1) };
    		    var id = new ClaimsIdentity(claims);
    		    await HttpContext.SignInAsync(&quot;a2&quot;, new ClaimsPrincipal(id), props);
    		    return Content(&quot;In2&quot;);
    	    }
    
    	    public async Task&lt;IActionResult&gt; Out1()
    	    {
    		    await HttpContext.SignOutAsync(CookieAuthenticationDefaults.AuthenticationScheme);
    		    return Content(&quot;Out1&quot;);
    		}
    
    	    public async Task&lt;IActionResult&gt; Out2()
    	    {
    		    await HttpContext.SignOutAsync(&quot;a2&quot;);
    		    return Content(&quot;Out2&quot;);
    	    }
    	}
    }

And Startup:

    namespace WebApplication1
    {
        public class Startup
        {
            public Startup(IConfiguration configuration)
            {
                Configuration = configuration;
            }
    
            public IConfiguration Configuration { get; }
    		
            public void ConfigureServices(IServiceCollection services)
            {
    			services.AddAuthentication(options =&gt;
    			{
    				options.DefaultScheme = CookieAuthenticationDefaults.AuthenticationScheme;
    		        })
    		        .AddCookie(CookieAuthenticationDefaults.AuthenticationScheme)
    		        .AddCookie(&quot;a2&quot;);
    
    			services.AddMvc();
            }
    		
            public void Configure(IApplicationBuilder app, IHostingEnvironment env)
            {
                app.UseAuthentication();
    
                app.UseMvc(routes =&gt;
                {
                    routes.MapRoute(name: &quot;default&quot;, template: &quot;{controller=Home}/{action=Index}/{id?}&quot;);
                });
            }
        }
    }




How do I setup multiple auth schemes in ASP.NET Core 2.0?

I was reading the announcement of entity framework core 2.0 https://blogs.msdn.microsoft.com/dotnet/2017/08/14/announcing-entity-framework-core-2-0/

It says that they added new Sql functions like `EF.Functions.Like` for performing the SQL `LIKE` operation.

I was wondering, what then would be the difference between `EF.Functions.Like` and `string.Contains`/`StartsWith`?

For example:

    var customers = context.Customers.Where(c =&gt; c.Name.StartsWith(&quot;a&quot;)); // Version A
    var customers = context.Customers.Where(c =&gt; EF.Functions.Like(c.Name, &quot;a%&quot;)); // Version B

What would be the difference between the two versions? 
EF already knows how to translate `string.Contains`/`StartsWith` to the corresponding SQL operations, doesn&#39;t it?

The only reason i can think of is that EF.Functions.Like would allow for more complex patterns like `&quot;a%b%&quot;` (although this one can be written as `StartsWith(&quot;a&quot;) &amp;&amp; Contains(&quot;b&quot;)`)

Is this the reason?

Entity framework EF.Functions.Like vs string.Contains

I am trying to download file from a URL and I have to choose between WebClient and HttpClient. I have referenced [this][1] article and several other articles on the internet. Everywhere, it is suggested to go for HttpClient due to its great async support and other .Net 4.5 privileges. But I am still not totally convinced and need more inputs. 

I am using below code to download file from internet:

**WebClient:**

    WebClient client = new WebClient();
    client.DownloadFile(downloadUrl, filePath);

**HttpClient:**

    using (HttpClient client = new HttpClient())
    {        
        using (HttpResponseMessage response = await client.GetAsync(url))
        using (Stream streamToReadFrom = await response.Content.ReadAsStreamAsync())
        {
    	}
    }

From my perspective, I can see only one disadvantage in using WebClient, that would be the non async call, blocking the calling thread. But what if I am not worried about the blocking of thread or use `client.DownloadFileAsync()` to leverage the async support? 

On the other hand, if I use HttpClient, ain&#39;t I loading every single byte of a file into memory and then writing it to a local file? If the file size is too large, won&#39;t memory overhead be expensive? Which could be avoided if we use WebClient, since it will directly write to local file and not consume system memory.

So, if performance is my utter priority, which approach should I use for download? I would like to be clarified if my above assumption is wrong, and I am open to alternate approach as well.

  [1]: https://stackoverflow.com/questions/20530152/deciding-between-httpclient-and-webclient

Download file with WebClient or HttpClient?

So far whenever I needed to use a conditional statement within a Widget I have done the following (Using Center and Containers as simplified dummy examples): 

    new Center(
      child: condition == true ? new Container() : new Container()
    )

Though when I tried using an if/else statement it would lead to an Dead code warning:

    new Center(
      child: 
        if(condition == true){
          new Container();
        }else{
          new Container();
        }
    )

Interestingly enough I tried with a switch case statement and it gives me the same warning and thus I cannot run the code. Am I doing something wrong or is it so that one cannot use if/else or switch statements without flutter thinking there is dead code?


How to use conditional statement within child attribute of a Flutter Widget (Center Widget)

I want to add a volume to my service, but only if the final user gave a folder for it. Otherwise, no volume should be mounted, for the already-prepared image has valid data in a default folder.

That is, I want to do something like (pseudocode):


    services:
    
      my_awesome_service:
      
        volumes:
          if ${VARIABLE} =&gt; ${VARIABLE}:/app/folder


**Are such conditional statements definable in a docker-compose file?** 

The only way I see to make this possible is to first define a base docker-compose file, which does not have the volume mount, and the call on a second docker-compose file only if the `$VARIABLE` is defined. This is fine for a single or few conditions, but gets nasty if there are many.


Any solution?





Content Type	Original Author	Original Content on Stackoverflow
Question	Boiethios	View Question on Stackoverflow
Solution 1 - C#	Mong Zhu	View Answer on Stackoverflow
Solution 2 - C#	ΦXocę 웃 Пepeúpa ツ	View Answer on Stackoverflow
Solution 3 - C#	Ajith Kumar	View Answer on Stackoverflow

How to check if a StringBuilder is empty?

C# Problem Overview

C# Solutions

Solution 1 - C#

Solution 2 - C#

Solution 3 - C#

How to implement Nested ListView in Flutter?

laravel Eloquent ORM delete() method

Attributions