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European ASP.NET Core Hosting :: Using Docker to Store ASP.NET Core Kestrel Certificates

clock March 22, 2019 08:48 by author Scott

When working with ASP.Net Core in Docker containers, it can be cumbersome to deal with certificates. While there is a documentation about setting certificate for dev environment, there’s no real guidance on how to make it work when deploying containers in a Swarm for example.
In this article we are going to see how to take advantage of Docker secrets to store ASP.Net Core Kestrel certificates in the context of Docker Swarm.

Hosting the service

First of all, we are going to create à Swarm service on our machine that use the sample Asp.Net Core app. The purpose of this article is to make SSL work in the container withoutchanging anything to an existing image.

docker service create --name mywebsite --publish published=8080,target=80,mode=host microsoft/dotnet-samples:aspnetapp

We are creating service mywebsite, publishing only one port 8080 bound to the port 80 in the container using the host mode and using the image microsoft/dotnet-samples:aspnetapp. Please note that you can use others configuration (for example expose port in routing mesh mode).

Preparing the certificate

We need a certificate. It can be created via an external certificate authority but here for the sake of the article, we are going to create a self signed certificate (of course, don’t use this in production). We are using Powershell for this task (you can skip this if you already have a pfx certificate signed by a real CA).

$cert = New-SelfSignedCertificate -DnsName "mywebsite" -CertStoreLocation "cert:\LocalMachine\My"
$password = ConvertTo-SecureString -String "mylittlesecret" -Force -AsPlainText
$cert | Export-PfxCertificate -FilePath c:\temp\mywebsite.pfx -Password $password

Once you have your pfx, we are goind to unprotect it from the password. It might be seem unsecure but when it will be added to the Docker secret store, it will be stored securedly. For this task I will use OpenSSL (not possible with Powerhsell as far as I know). OpenSSL is provided with Git for example.

& 'C:\Program Files\Git\mingw64\bin\openssl.exe' pkcs12 -in c:\temp\mywebsite.pfx -nodes -out c:\temp\mywebsite.pem -passin pass:mylittlesecret
& 'C:\Program Files\Git\mingw64\bin\openssl.exe' pkcs12 -export -in c:\temp\mywebsite.pem -out c:\temp\mywebsite.unprotected.pfx -passout pass:

Now that the pfx is un protected, we can add it to the docker store certificate and display it.

docker secret create kestrelcertificate c:\temp\mywebsite.unprotected.pfx

docker secret ls

ID                          NAME                 DRIVER              CREATED             UPDATED

iapy6rolt7po1mwm9aw6z0qc5   kestrelcertificate                       13 minutes ago      13 minutes ago

Our secret being in the store, you can delete (or store securely somewhere else your pfx).

Making it work

We can now update our service to take in account this secret. When adding a secret to a service, Docker will create a file in a specific directory containing the value of the secret. On Windows it’s c:\programdata\docker\secrets.

Let’s update our service and see what happened inside the container.

docker service update --secret-add kestrelcertificate mywebsite

docker exec 4b51e736ce65 cmd.exe /c dir c:\programdata\docker\secrets

 Volume in drive C has no label.
 Volume Serial Number is 3CBB-E577

 Directory of c:\programdata\docker\secrets

11/15/2018  10:38 PM    <DIR>          .
11/15/2018  10:38 PM    <DIR>          ..
11/15/2018  10:38 PM    <SYMLINK>      kestrelcertificate [C:\ProgramData\Docker\internal\secrets\iapy6rolt7po1mwm9aw6z0qc5]
               1 File(s)              0 bytes
               2 Dir(s)  21,245,009,920 bytes free

We can see that our secret exists and is named kestrelcertificate, as we named it in the command line.

We can therefore update our service to remove the old binding on port 80, replace it with a binding on port 443, tell Kestrel to use this port and finally give Kestrel the path of our secret.
This can be done with only one command:

docker service update --publish-rm published=8080,target=80,mode=host --publish-add published=8080,target=443,mode=host --env-add ASPNETCORE_URLS=https://+:443 --env-add Kestrel__Certificates__Default__Path=c:\programdata\docker\secrets\kestrelcertificate mywebsite

Wait a while that your service update, try to browse and it should work ! Well, actually it should only works on Linux.

Making it work on Windows

If you try to have a look a the logs generated by your service, you should end with something like this.

docker service logs mywebsite

mywebsite.1.uy3vm8txwxec@nmarchand-lt    | crit: Microsoft.AspNetCore.Server.Kestrel[0]
mywebsite.1.uy3vm8txwxec@nmarchand-lt    |       Unable to start Kestrel.
mywebsite.1.uy3vm8txwxec@nmarchand-lt    | Internal.Cryptography.CryptoThrowHelper+WindowsCryptographicException: Unspecified error
mywebsite.1.uy3vm8txwxec@nmarchand-lt    |    at Internal.Cryptography.Pal.CertificatePal.FromBlobOrFile(Byte[] rawData, String fileName, SafePasswordHandle password, X509KeyStorageFlags keyStorageFlags)
mywebsite.1.uy3vm8txwxec@nmarchand-lt    |    at System.Security.Cryptography.X509Certificates.X509Certificate..ctor(String fileName, String password, X509KeyStorageFlags keyStorageFlags)
mywebsite.1.uy3vm8txwxec@nmarchand-lt    |    at System.Security.Cryptography.X509Certificates.X509Certificate2..ctor(String fileName, String password)
mywebsite.1.uy3vm8txwxec@nmarchand-lt    |    at Microsoft.AspNetCore.Server.Kestrel.KestrelConfigurationLoader.LoadCertificate(CertificateConfig certInfo, String endpointName)
mywebsite.1.uy3vm8txwxec@nmarchand-lt    |    at Microsoft.AspNetCore.Server.Kestrel.KestrelConfigurationLoader.LoadDefaultCert(ConfigurationReader configReader)
mywebsite.1.uy3vm8txwxec@nmarchand-lt    |    at Microsoft.AspNetCore.Server.Kestrel.KestrelConfigurationLoader.Load()
mywebsite.1.uy3vm8txwxec@nmarchand-lt    |    at Microsoft.AspNetCore.Server.Kestrel.Core.KestrelServer.ValidateOptions()
mywebsite.1.uy3vm8txwxec@nmarchand-lt    |    at Microsoft.AspNetCore.Server.Kestrel.Core.KestrelServer.StartAsync[TContext](IHttpApplication`1 application, CancellationToken cancellationToken)
mywebsite.1.uy3vm8txwxec@nmarchand-lt    |
mywebsite.1.uy3vm8txwxec@nmarchand-lt    | Unhandled Exception: Internal.Cryptography.CryptoThrowHelper+WindowsCryptographicException: Unspecified error
mywebsite.1.uy3vm8txwxec@nmarchand-lt    |    at Internal.Cryptography.Pal.CertificatePal.FromBlobOrFile(Byte[] rawData, String fileName, SafePasswordHandle password, X509KeyStorageFlags keyStorageFlags)
mywebsite.1.uy3vm8txwxec@nmarchand-lt    |    at System.Security.Cryptography.X509Certificates.X509Certificate..ctor(String fileName, String password, X509KeyStorageFlags keyStorageFlags)
mywebsite.1.uy3vm8txwxec@nmarchand-lt    |    at System.Security.Cryptography.X509Certificates.X509Certificate2..ctor(String fileName, String password)
mywebsite.1.uy3vm8txwxec@nmarchand-lt    |    at Microsoft.AspNetCore.Server.Kestrel.KestrelConfigurationLoader.LoadCertificate(CertificateConfig certInfo, String endpointName)
mywebsite.1.uy3vm8txwxec@nmarchand-lt    |    at Microsoft.AspNetCore.Server.Kestrel.KestrelConfigurationLoader.LoadDefaultCert(ConfigurationReader configReader)
mywebsite.1.uy3vm8txwxec@nmarchand-lt    |    at Microsoft.AspNetCore.Server.Kestrel.KestrelConfigurationLoader.Load()
mywebsite.1.uy3vm8txwxec@nmarchand-lt    |    at Microsoft.AspNetCore.Server.Kestrel.Core.KestrelServer.ValidateOptions()
mywebsite.1.uy3vm8txwxec@nmarchand-lt    |    at Microsoft.AspNetCore.Server.Kestrel.Core.KestrelServer.StartAsync[TContext](IHttpApplication`1 application, CancellationToken cancellationToken)
mywebsite.1.uy3vm8txwxec@nmarchand-lt    |    at Microsoft.AspNetCore.Hosting.Internal.WebHost.StartAsync(CancellationToken cancellationToken)
mywebsite.1.uy3vm8txwxec@nmarchand-lt    |    at Microsoft.AspNetCore.Hosting.WebHostExtensions.RunAsync(IWebHost host, CancellationToken token, String shutdownMessage)
mywebsite.1.uy3vm8txwxec@nmarchand-lt    |    at Microsoft.AspNetCore.Hosting.WebHostExtensions.RunAsync(IWebHost host, CancellationToken token)
mywebsite.1.uy3vm8txwxec@nmarchand-lt    |    at Microsoft.AspNetCore.Hosting.WebHostExtensions.Run(IWebHost host)
mywebsite.1.uy3vm8txwxec@nmarchand-lt    |    at aspnetapp.Program.Main(String[] args) in C:\app\aspnetapp\Program.cs:line 18

We can see a nasty bug of Windows here (Github issue).
What did happen ? If you look closely at the dir command we made in the container, you’ll see that the secret is not really a file but instead a symbolic link to an other file. Unfortunately, Windows is unable to use a certificate that is a symlink. One solution could be to manually read the certificate with File.ReadAllBytes() and pass it to the constructor of X509Certificate. However, it would be against the purpose of this article which is to not modify the Docker image.

We can find a workaround by browsing the Docker documentation which states that the real file containing the secret (which in fact is the target of the symlink) can be found in the path c:\programdata\docker\internal\secrets\<secretid> where secretid is the id of the secret (as shown by docker secret ls).

We can update our service to change the path by updating the environment variable. It now works also on windows!

docker service update --env-rm
Kestrel__Certificates__Default__Path=c:\programdata\docker\secrets\kestrelcertificate --env-add Kestrel__Certificates__Default__Path=c:\programdata\docker\internal\secrets\iapy6rolt7po1mwm9aw6z0qc5 mywebsite

docker logs 7b54cdc42a86

Hosting environment: Production
Content root path: C:\app
Now listening on: https://[::]:443
Application started. Press Ctrl+C to shut down.

Final word

We have seen in this article how to use Docker secrets to store ASP.Net Core Kestrel certificates in our Docker Swarm. However, please keep in mind that the Windows workaround should be used with care as written in the Docker documentation.

Another word also about SSL Offloading : I know that usually the reverse proxy (Nginx, Traefik, etc.) is used to be the SSL termination but sometimes you still want SSL end to end. 



European ASP.NET Core Hosting :: ASP.NET Core with MySQL and Entity Framework Core

clock March 14, 2019 07:58 by author Scott

This article shows how to use MySQL with ASP.NET Core 2.1 using Entity Framework Core.

The Entity Framework MySQL package can be downloaded using the NuGet package Pomelo.EntityFrameworkCore.MySql. At present no official provider from MySQL exists for Entity Framework Core which can be used in an ASP.NET Core application.

The Pomelo.EntityFrameworkCore.MySql package can be added to the csproj file.

<Project Sdk="Microsoft.NET.Sdk"> 

  <PropertyGroup>
    <TargetFramework>netcoreapp2.2</TargetFramework>
    <AssemblyName>DataAccessMySqlProvider</AssemblyName>
    <PackageId>DataAccessMySqlProvider</PackageId>
  </PropertyGroup> 

  <ItemGroup>
    <ProjectReference Include="..\DomainModel\DomainModel.csproj" />
  </ItemGroup> 

  <ItemGroup>
    <PackageReference Include="Microsoft.AspNetCore.App"  />
    <PackageReference Include="Microsoft.EntityFrameworkCore.Tools" Version="2.2.0" PrivateAssets="All" />
    <PackageReference Include="Pomelo.EntityFrameworkCore.MySql" Version="2.0.1" />
  </ItemGroup> 

  <ItemGroup>
    <Folder Include="Properties\" />
  </ItemGroup> 

</Project>

The web project which loads the project with EF Core needs to support migrations if you wish to create a database this way.

<Project Sdk="Microsoft.NET.Sdk.Web"> 

  <PropertyGroup>
    <TargetFramework>netcoreapp2.1</TargetFramework>
    <AssemblyName>AspNetCoreMultipleProject</AssemblyName>
    <PackageId>AspNet5MultipleProject</PackageId>
  </PropertyGroup> 

  <ItemGroup>
    <Content Update="wwwroot\**\*;Views;Areas\**\Views;appsettings.json;config.json;web.config">
      <CopyToPublishDirectory>PreserveNewest</CopyToPublishDirectory>
    </Content>
  </ItemGroup> 

  <ItemGroup>
    <ProjectReference Include="..\DataAccessMsSqlServerProvider\DataAccessMsSqlServerProvider.csproj" />
    <ProjectReference Include="..\DataAccessMySqlProvider\DataAccessMySqlProvider.csproj" />
    <ProjectReference Include="..\DataAccessPostgreSqlProvider\DataAccessPostgreSqlProvider.csproj"
/>
    <ProjectReference Include="..\DataAccessSqliteProvider\DataAccessSqliteProvider.csproj" />
    <ProjectReference Include="..\DomainModel\DomainModel.csproj" />
  </ItemGroup>   

  <ItemGroup>
    <PackageReference Include="Microsoft.AspNetCore.App"  />
    <PackageReference Include="Microsoft.EntityFrameworkCore.Tools" Version="2.2.0" PrivateAssets="All" />
  </ItemGroup>
  <ItemGroup>
    <DotNetCliToolReference Include="Microsoft.VisualStudio.Web.CodeGeneration.Tools" Version="2.0.0" />
  </ItemGroup>
    <ItemGroup>
      <Folder Include="Migrations\" />
    </ItemGroup>
</Project>

An EfCore DbContext can be added like any other context supported by Entity Framework Core.

using System;
using System.Linq;
using DomainModel.Model;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Configuration; 

namespace DataAccessMySqlProvider
{
    // >dotnet ef migration add testMigration
    public class DomainModelMySqlContext : DbContext
    {
        public DomainModelMySqlContext(DbContextOptions<DomainModelMySqlContext> options) :base(options)
        { }         

        public DbSet<DataEventRecord> DataEventRecords { get; set; } 

        public DbSet<SourceInfo> SourceInfos { get; set; } 

        protected override void OnModelCreating(ModelBuilder builder)
        {
            builder.Entity<DataEventRecord>().HasKey(m => m.DataEventRecordId);
            builder.Entity<SourceInfo>().HasKey(m => m.SourceInfoId); 

            // shadow properties
            builder.Entity<DataEventRecord>().Property<DateTime>("UpdatedTimestamp");
            builder.Entity<SourceInfo>().Property<DateTime>("UpdatedTimestamp"); 

            base.OnModelCreating(builder);
        } 

        public override int SaveChanges()
        {
            ChangeTracker.DetectChanges(); 

            updateUpdatedProperty<SourceInfo>();
            updateUpdatedProperty<DataEventRecord>(); 

            return base.SaveChanges();
        } 

        private void updateUpdatedProperty<T>() where T : class
        {
            var modifiedSourceInfo =
                ChangeTracker.Entries<T>()
                    .Where(e => e.State == EntityState.Added || e.State == EntityState.Modified); 

            foreach (var entry in modifiedSourceInfo)
            {
                entry.Property("UpdatedTimestamp").CurrentValue = DateTime.UtcNow;
            }
        }
    }
}

In an ASP.NET Core web application, the DbContext is added to the application in the startup class. In this example, the DbContext is defined in a different class library. The MigrationsAssembly needs to be defined, so that the migrations will work. If the context and the migrations are defined in the same assembly, this is not required.

public Startup(IHostingEnvironment env)
{
    var builder = new ConfigurationBuilder()
        .SetBasePath(env.ContentRootPath)
        .AddJsonFile("appsettings.json", optional: true, reloadOnChange: true)
        .AddJsonFile("config.json", optional: true, reloadOnChange: true); 

    Configuration = builder.Build();
}         
public void ConfigureServices(IServiceCollection services)
{  
    var sqlConnectionString = Configuration.GetConnectionString("DataAccessMySqlProvider"); 

    services.AddDbContext<DomainModelMySqlContext>(options =>
        options.UseMySQL(
            sqlConnectionString,
            b => b.MigrationsAssembly("AspNetCoreMultipleProject")
        )
    );
}

The application uses the configuration from the config.json. This file is used to get the MySQL connection string, which is used in the Startup class.

{
    "ConnectionStrings": { 
        "DataAccessMySqlProvider": "server=localhost;userid=store;password=3333;database=store;"
        }
    }
}

MySQL workbench can be used to add the schema ‘store to the MySQL database. The user ‘store is also required, which must match the defined user in the connection string. If you configure the MySQL database differently, then you need to change the connection string in the config.json file.

Now the database migrations can be created and the database can be updated.

>
> dotnet ef migrations add mySqlMigration --context DomainModelMySqlContext
>
> dotnet ef database update --context DomainModelMySqlContext
>

If successful, the tables are created.

The MySQL provider can be used in a MVC controller using construction injection.

using System.Collections.Generic;
using DomainModel;
using DomainModel.Model;
using Microsoft.AspNetCore.Mvc;
using Newtonsoft.Json; 

namespace AspNet5MultipleProject.Controllers
{
    [Route("api/[controller]")]
    public class DataEventRecordsController : Controller
    {
        private readonly IDataAccessProvider _dataAccessProvider; 

        public DataEventRecordsController(IDataAccessProvider dataAccessProvider)
        {
            _dataAccessProvider = dataAccessProvider;
        } 

        [HttpGet]
        public IEnumerable<DataEventRecord> Get()
        {
            return _dataAccessProvider.GetDataEventRecords();
        } 

        [HttpGet]
        [Route("SourceInfos")]
        public IEnumerable<SourceInfo> GetSourceInfos(bool withChildren)
        {
            return _dataAccessProvider.GetSourceInfos(withChildren);
        } 

        [HttpGet("{id}")]
        public DataEventRecord Get(long id)
        {
            return _dataAccessProvider.GetDataEventRecord(id);
        } 

        [HttpPost]
        public void Post([FromBody]DataEventRecord value)
        {
            _dataAccessProvider.AddDataEventRecord(value);
        } 

        [HttpPut("{id}")]
        public void Put(long id, [FromBody]DataEventRecord value)
        {
            _dataAccessProvider.UpdateDataEventRecord(id, value);
        } 

        [HttpDelete("{id}")]
        public void Delete(long id)
        {
            _dataAccessProvider.DeleteDataEventRecord(id);
        }
    }
}

The controller api can be called using Fiddler:

POST http://localhost:5000/api/dataeventrecords HTTP/1.1
User-Agent: Fiddler
Host: localhost:5000
Content-Length: 135
Content-Type: application/json;  

{
  "DataEventRecordId":3,
  "Name":"Funny data",
  "Description":"yes",
  "Timestamp":"2015-12-27T08:31:35Z",
   "SourceInfo":
  {
    "SourceInfoId":0,
    "Name":"Beauty",
    "Description":"second Source",
    "Timestamp":"2015-12-23T08:31:35+01:00",
    "DataEventRecords":[]
  },
 "SourceInfoId":0
}

The data is added to the database as required.



European ASP.NET Core Hosting :: Smart Logging Middleware for ASP.NET Core

clock March 13, 2019 09:44 by author Scott

ASP.NET Core comes with request logging built-in. This is great for getting an app up-and-running, but the events are not as descriptive or efficient as hand-crafted request logging can be. Here is a typical trace from a single GET request to /about:



If the request fails because of an error, you'll see instead:



While these fine-grained events are sometimes useful, they take up storage space and bandwidth, and add noise to the log.

Spreading the information across many events also makes it harder to perform some analyses, for example, the HTTP method and elapsed time are on different events, making it hard to separate the timings of GET and POST requests to the same RequestPath.

In production we want:

One "infrastructure" event per normal request, with basic HTTP information attached

Extra information to help with debugging if a request fails due to a server-side (5xx) error

The same format and event type for all requests, so that logs from both successful and failed requests can be easily grouped, sorted and analyzed together

Here's the format we're aiming for, expanded so that you can see all of the attached properties:

Instead of five infrastructure events + one application event, just a single infrastructure event is logged. This makes the application's own "Hello" event much easier to spot.

This post includes the full source code for the middleware, so you can take it and modify it to include the information you find most useful.

Step 1: Install and Configure Serilog

ASP.NET Core includes some basic logging providers, but to get the most out of it you'll need to plug in a full logging framework like Serilog. If you haven't done that already, these instructions should have you up and running quickly.

Step 2: Turn off Information events from Microsoft and System

Where Serilog is configured, add level overrides for the Microsoft and System namespaces:

Log.Logger = new LoggerConfiguration() 
    .MinimumLevel.Override("Microsoft", LogEventLevel.Warning)
    .MinimumLevel.Override("System", LogEventLevel.Warning)
    // Other logger configuration

These can be turned back on for debugging when they're needed.

If you're using appsettings.json configuration, check out the level overrides example in the README.

Step 3: Add the SerilogMiddleware class

The SerilogMiddleware class hooks into the request processing pipeline to collect information about the requests:

using Microsoft.AspNetCore.Http; 
using Serilog; 
using Serilog.Events; 
using System; 
using System.Collections.Generic; 
using System.Diagnostics; 
using System.Linq; 
using System.Threading.Tasks;

namespace Datalust.SerilogMiddlewareExample.Diagnostics 
{
    class SerilogMiddleware
    {
        const string MessageTemplate =
            "HTTP {RequestMethod} {RequestPath} responded {StatusCode} in {Elapsed:0.0000} ms";

        static readonly ILogger Log = Serilog.Log.ForContext<SerilogMiddleware>();

        readonly RequestDelegate _next;

        public SerilogMiddleware(RequestDelegate next)
        {
            if (next == null) throw new ArgumentNullException(nameof(next));
            _next = next;
        }

        public async Task Invoke(HttpContext httpContext)
        {
            if (httpContext == null) throw new ArgumentNullException(nameof(httpContext));

            var sw = Stopwatch.StartNew();
            try
            {
                await _next(httpContext);
                sw.Stop();

                var statusCode = httpContext.Response?.StatusCode;
                var level = statusCode > 499 ? LogEventLevel.Error : LogEventLevel.Information;

                var log = level == LogEventLevel.Error ? LogForErrorContext(httpContext) : Log;
                log.Write(level, MessageTemplate, httpContext.Request.Method, httpContext.Request.Path, statusCode, sw.Elapsed.TotalMilliseconds);
            }
            // Never caught, because `LogException()` returns false.
            catch (Exception ex) when (LogException(httpContext, sw, ex)) { }
        }

        static bool LogException(HttpContext httpContext, Stopwatch sw, Exception ex)
        {
            sw.Stop();

            LogForErrorContext(httpContext)
                .Error(ex, MessageTemplate, httpContext.Request.Method, httpContext.Request.Path, 500, sw.Elapsed.TotalMilliseconds);

            return false;
        }

        static ILogger LogForErrorContext(HttpContext httpContext)
        {
            var request = httpContext.Request;

            var result = Log
                .ForContext("RequestHeaders", request.Headers.ToDictionary(h => h.Key, h => h.Value.ToString()), destructureObjects: true)
                .ForContext("RequestHost", request.Host)
                .ForContext("RequestProtocol", request.Protocol);

            if (request.HasFormContentType)
                result = result.ForContext("RequestForm", request.Form.ToDictionary(v => v.Key, v => v.Value.ToString()));

            return result;
        }
    }
}

I've deliberately kept this to a single (somewhat ugly!) source file so that it's easy to copy, paste and modify.

There are a lot of design details and trade-offs involved. You can see that when a request is deemed to have failed, some additional information is attached, including the headers sent by the client, and the form data if any.

Step 4: Add the middleware to the pipeline

In your application's Startup.cs file, you can add the middleware either before or after the outermost exception handling components. If you add it before this, you won't get the full Exception information in any error events, but you will always be able to record the exact status code returned to the client. Adding the middleware into the pipeline inside the exception handling components (i.e., after them in the source code) will provide all exception detail but has to assume that the status code is 500 in this case.

public void Configure(IApplicationBuilder app, IHostingEnvironment env, 
                      ILoggerFactory loggerFactory)
{
    loggerFactory.AddSerilog();

    if (env.IsDevelopment())
    {
        app.UseDeveloperExceptionPage();
        app.UseBrowserLink();
    }
    else
    {
        app.UseExceptionHandler("/Home/Error");
    }

    app.UseMiddleware<SerilogMiddleware>();

    app.UseStaticFiles();

    app.UseMvc(routes =>
    {
        routes.MapRoute(
            name: "default",
            template: "{controller=Home}/{action=Index}/{id?}");
    });
}

Step 5: Profit!

Now you have a stream of request log events each with paths, status codes, timings, and exceptions:

We've seen how a simple customized logging strategy can not only produce cleaner events, but also reduce the volume of infrastructure log events.



ASP.NET Core Hosting :: How to Upload File using C# | SFTP Server

clock March 4, 2019 07:56 by author Scott

Although there are many Graphical Tools available for sending files to a server using SFTP. But as a developer, we may have a scenario where we need to upload a file to SFTP Serverfrom our Code.

A few days ago a job assigned to me was to develop a Task Scheduler for generating XML files daily on a specific time of the day & send these files on a Remote Server using File Transfer Protocol in a secure way.

In .Net Framework there are many Libraries available for uploading files to another machine using File Transfer Protocol but most of the libraries don’t work with .Net Core. In this Tutorial, we will develop a very simple SFTP client using C# for .Net Core.

Before start let’s have a quick look at SFTP.

What is SFTP?

SFTP stands for SSH File Transfer Protocol or Secure File Transfer Protocol. It is a protocol used to transfer files between remote machines over a secure shell.

 

In almost all cases, SFTP is preferable over FTP because of security features. FTP is not a secure protocol & it should only be used on a trusted network.

Choosing Library for C#

A lot of search & after testing many libraries I finally met with SSH.NET which was working perfectly with .Net Core 2.2 project & the good thing was that It does its job in a very few lines of Code.

So we’ll use SSH.NET

What is SSH.NET?

SSH.NET is an open-source library available at Nuget for .NET to work over SFTP. It is also optimized for parallelism to achieve the best possible performance. It was inspired by Sharp.SSH library which was ported from Java. This library is a complete rewrite using .Net, without any third party dependencies.

Here are the features of SSH.NET: 

Creating Project

I’m in love with VS Code right after its first release so I’m going to use VS Code for creating project to upload/transfer a file to a remote server using SFTP.

Create a console application using this command

dotnet new console

Installing SSH.NET

I won’t recommend you to install the latest version of SSH.NET. It has a bug, it can be stuck on transferring the file to the remote location.

version 2016.0.0 is perfect. 

run this command to install the library from NuGet

using package manager

Install-Package SSH.NET -Version 2016.0.0

or using .Net CLI

dotnet add package SSH.NET --version 2016.0.0

Code

Finally, It’s time to create a class for SFTP Client Code.

Create a file with the name as “SendFileToServer” & add the below code

using Renci.SshNet

public static class SendFileToServer
{
// Enter your host name or IP here
private static string host = "127.0.0.1";

// Enter your sftp username here
private static string username = "sftp";

// Enter your sftp password here
private static string password = "12345";
public static int Send(string fileName)
{
var connectionInfo = new ConnectionInfo(host, "sftp", new PasswordAuthenticationMethod(username, password));

// Upload File
using (var sftp = new SftpClient(connectionInfo)){

sftp.Connect();
//sftp.ChangeDirectory("/MyFolder");
using (var uplfileStream = System.IO.File.OpenRead(fileName)){
sftp.UploadFile(uplfileStream, fileName, true);
}
sftp.Disconnect();
}
return 0;
}
}

Now you can call this Method to transfer a file to SFTP Server like this

SendFileToServer.Send("myFile.txt");

“myFile.txt” is the name of the file which should be located in your project root directory. 



European ASP.NET Core Hosting :: How to Use HTTP-REPL tool to test WEB API in ASP.NET Core 2.2

clock February 26, 2019 07:37 by author Scott

Today there are no tools built into Visual Studio to test WEB API. Using browsers, one can only test http GET requests. You need to use third-party tools like PostmanSoapUIFiddler or Swagger to perform a complete testing of the WEB API. In ASP.NET Core 2.2, a CLI based new dotnet core global tool named “http-repl” is introduced to interact with API endpoints. It’s a CLI based tool which can list down all the routes and execute all HTTP verbs. In this post, let’s find out how to use HTTP-REPL tool to test WEB API in ASP.NET Core 2.2.

HTTP-REPL Tool to test WEB API in ASP.NET Core 2.2

The “http-repl” is a dotnet core global tool and to install this tool, run the following command. At the time of writing this post, the http-repl tool is in preview stage
and available for download at 
dotnet.myget.org

dotnet tool install -g dotnet-httprepl --version 2.2.0-* --add-source https://dotnet.myget.org/F/dotnet-core/api/v3/index.json

Once installed, you can verify the installation using the following command.

dotnet tool list -g



Now the tool is installed, let’s see how we can test the WEB API. For this tool to work properly, the prerequisite here is that your services will have Swagger/OpenAPI available that describes the service.

We need to add this tool to web browser list so that we can browse the API with this tool. To do that, follow the steps given in the below image.



The location of HTTP-REPL tool executable is "C:\Users\<username>\.dotnet\tools". Once added, you can verify it in the browser list.

Run the app (make sure HTTP REPL is selected in browser list) and you should see a command prompt window. As mentioned earlier, it’s a CLI based experience so you can use commands like dir, ls, cdand cls. Below is an example run where I start-up a Web API.

You can use all the HTTP Verbs, and when using the POST verb, you should set a default text editor to supply the JSON. You can set Visual Studio Code as default text editor using the following command.

pref set editor.command.default "C:\Program Files (x86)\Microsoft VS Code\Code.exe"

Once the default editor is set, and you fire POST verb, it will launch the editor with the JSON written for you. See below GIF.

You can also navigate to the Swagger UI from the command prompt via executing ui command. Like,

Similarly, you can also execute the DELETE and PUT. In case of PUT command, you should use following syntax and in the default code editor, supply the updated data.

> delete 2 //This would delete the record with id 2.
>
> put 2010 -h "Content-Type: application/json"

When you fire PUT command, the behavior is same as the POST verb. The text editor will open with the JSON written for you, just supply the updated value to execute PUT command.

Pros and Cons

Pros

  • Helps in debugging WEB API
  • Fast and quickly switch between API endpoints
  • Descriptive error response shown

Cons:

  • Dependency on Swagger/Open API specification
  • Not as informative as UI tools

After playing with this for a while, I strongly feel it’s command line version of the Swagger UI and it would be very handy when there are many API endpoints. You can easily navigate or switch between the APIs and execute it. 



European ASP.NET Core Hosting :: ASP.NET Core 2.0 MVC Filters

clock January 28, 2019 09:58 by author Scott

The following is tutorial how to run code before and after MVC request pipeline in ASP.NET Core.

Solution

In an empty project update Startup class to add services and middleware for MVC:

        public void ConfigureServices
            (IServiceCollection services)
        {
            services.AddMvc();
        } 

        public void Configure(
            IApplicationBuilder app,
            IHostingEnvironment env)
        {
            app.UseMvc(routes =>
            {
                routes.MapRoute(
                    name: "default",
                    template: "{controller=Home}/{action=Index}/{id?}");
            });
        }

Add the class to implement filter:

    public class ParseParameterActionFilter : Attribute, IActionFilter
    {
        public void OnActionExecuting(ActionExecutingContext context)
        {
            object param;
            if (context.ActionArguments.TryGetValue("param", out param))
                context.ActionArguments["param"] = param.ToString().ToUpper();
            else
                context.ActionArguments.Add("param", "I come from action filter");
        } 

        public void OnActionExecuted(ActionExecutedContext context)
        {
        }
    }

In the Home controller add an action method that uses Action filter:

        [ParseParameterActionFilter]
        public IActionResult ParseParameter(string param)
        {
            return Content($"Hello ParseParameter. Parameter: {param}");
        }

Browse to /Home/ParseParameter, you’ll see:

 

Discussion

Filter runs after an action method has been selected to execute. MVC provides built-in filters for things like authorisation and caching. Custom filters are very useful to encapsulate reusable code that you want to run before or after action methods.

Filters can short-circuit the result i.e. stops the code in your action from running and return a result to the client. They can also have services injected into them via service container, which makes them very flexible.

Filter Interfaces

Creating a custom filter requires implementing an interface for the type of filter you require. There are two flavours of interfaces for most filter type, synchronous and asynchronous:

    public class HelloActionFilter : IActionFilter
    {
        public void OnActionExecuting(ActionExecutingContext context)
        {
            // runs before action method
        } 

        public void OnActionExecuted(ActionExecutedContext context)
        {
            // runs after action method
        }
    } 

    public class HelloAsyncActionFilter : IAsyncActionFilter
    {
        public async Task OnActionExecutionAsync(
            ActionExecutingContext context,
            ActionExecutionDelegate next)
        {
            // runs before action method
            await next();
            // runs after action method
        }
    }

You can short-circuit the filter pipeline by setting the Result (of type IActionResult) property on context parameter (for Async filters don’t call the next delegate):

    public class SkipActionFilter : Attribute, IActionFilter
    {
        public void OnActionExecuting(ActionExecutingContext context)
        {
            context.Result = new ContentResult
            {
                Content = "I'll skip the action execution"
            };
        } 

        public void OnActionExecuted(ActionExecutedContext context)
        { }
    } 

    [SkipActionFilter]
    public IActionResult SkipAction()
    {
       return Content("Hello SkipAction");
    }

For Result filters you could short-circuit by setting the Cancel property on context parameter and sending a response:

        public void OnResultExecuting(ResultExecutingContext context)
        {
            context.Cancel = true;
            context.HttpContext.Response.WriteAsync("I'll skip the result execution");
        } 

        [SkipResultFilter]
        public IActionResult SkipResult()
        {
            return Content("Hello SkipResult");
        }

Filter Attributes

MVC provides abstract base classes that you can inherit from to create custom filters. These abstract classes inherit from Attribute class and therefore can be used to decorate controllers and action methods:

  • ActionFilterAttribute
  • ResultFilterAttribute
  • ExceptionFilterAttribute
  • ServiceFilterAttribute
  • TypeFilterAttribute

Filter Types

There are various type of filters that run at different stages of the filter pipeline. Below a figure from official documentation illustrates the sequence:

 

 

Authorization

 

 

This is the first filter to run and short circuits request for unauthorised users. They only have one method (unlike most other filters that have Executing and Executed methods). Normally you won’t write your own Authorization filters, the built-in filter calls into framework’s authorisation mechanism.

Resource

They run before model binding and can be used for changing how it behaves. Also they run after the result has been generated and can be used for caching etc.

Action

They run before and after the action method, thus are useful to manipulate action parameters or its result. The context supplied to these filters let you manipulate the action parameters, controller and result.

Exception

They can be used for unhandled exception before they’re written to the response. Exception handling middleware works for most scenarios however this filter can be used if you want to handle errors differently based on the invoked action.

Result

They run before and after the execution of action method’s result, if the result was successful. They can be used to manipulate the formatting of result.

Filter Scope

Filters can be added at different levels of scope: Action, Controller and Global. Attributes are used for action and controller level scope. For globally scoped filters you need to add them to filter collection of MvcOptions when configuring services in Startup:

            services.AddMvc(options =>
            {
                             // by instance
                options.Filters.Add(new AddDeveloperResultFilter("Tahir Naushad")); 

                // by type
                options.Filters.Add(typeof(GreetDeveloperResultFilter));
            });

Filters are executed in a sequence:

1. The Executing methods are called first for Global > Controller > Action filters.

2. Then Executed methods are called for Action > Controller > Global filters.

Filter Dependency Injection

In order to use filters that require dependencies injected at runtime, you need to add them by Type. You can add them globally (as illustrated above), however, if you want to apply them to action or controller (as attributes) then you have two options:

ServiceFilterAttribute

This attributes retrieves the filter using service container. To use it:

Create a filter that uses dependency injection:

    public class GreetingServiceFilter : IActionFilter
    {
        private readonly IGreetingService greetingService; 

        public GreetingServiceFilter(IGreetingService greetingService)
        {
            this.greetingService = greetingService;
        } 
        public void OnActionExecuting(ActionExecutingContext context)
        {
            context.ActionArguments["param"] =
                this.greetingService.Greet("James Bond");
        } 

        public void OnActionExecuted(ActionExecutedContext context)
        { }
    }

Add filter to service container:

services.AddScoped<GreetingServiceFilter>();

Apply it using ServiceFilterAttribute:

[ServiceFilter(typeof(GreetingServiceFilter))]
public IActionResult GreetService(string param)

TypeFilterAttribute

This attributes doesn’t need registering the filter in service container and initiates the type using ObjectFactory delegate. To use it:

Create a filter that uses dependency injection:

    public class GreetingTypeFilter : IActionFilter
    {
        private readonly IGreetingService greetingService; 

        public GreetingTypeFilter(IGreetingService greetingService)
        {
            this.greetingService = greetingService;
        } 

        public void OnActionExecuting(ActionExecutingContext context)
        {
            context.ActionArguments["param"] = this.greetingService.Greet("Dr. No");
        } 

        public void OnActionExecuted(ActionExecutedContext context)
        { }
    }

Apply it using TypeFilterAttribute:

[TypeFilter(typeof(GreetingTypeFilter))]
public IActionResult GreetType1(string param)

You could also inherit from TypeFilterAttribute and then use without TypeFilter:

public class GreetingTypeFilterWrapper : TypeFilterAttribute
{
   public GreetingTypeFilterWrapper() : base(typeof(GreetingTypeFilter))
   { }


[GreetingTypeFilterWrapper]
public IActionResult GreetType2(string param)
 



European ASP.NET Core Hosting - HostForLIFE.eu :: How to Setup Webpack in ASP.NET Core

clock February 10, 2017 11:11 by author Scott

Webpack is a great tool for bundling the client side assets in your web application. In this post we'll briefly discuss why you should create bundles and see how Webpack can automate that for us in ASP.NET Core.

Why should I bundle

When building web applications, regardless of the server side framework, you'll need to get your client side resources over to the browser. You may have dozens of JavaScript and CSS files in your project but having to reference each of them individually in your HTML markup is just not ideal for production deployments.

Each browser only allows so many concurrent requests per hostname. BrowserScope has some data on this that you can view on their site. If your web application makes more than the allowed number of simultaneous requests then the additional requests will end up being queued. This leads to longer load times and a not so smooth experience for your users; especially on mobile devices.

It would be much better to group resources into bundles so that the browser would have fewer files to download and thus fewer requests to make. This will help in keeping bandwidth usage low and even with battery life on your users' devices.

What is Webpack?

Webpack is a module bundler for the static assets in your web application. Essentially, you point Webpack at the main entry point(s) of your code then it will determine the dependencies, run transformations and create bundles that you can provide to your browser. What's even better is that in addition to JavaScript Webpack can also handle CSS, LESS, TypeScript, CoffeeScript, images, web fonts and more.

Setting up

We're going to start by setting up a new ASP.NET Core project using the dotnet cli tooling. If you don't have tooling installed, you can find can setup files and instructions here. If you're not a Windows user, the tooling works on Windows, OSX and Linux so no need to worry.

Let's get started by opening a terminal and creating an empty directory. Now, we'll generate a new ASP.NET Core project by running the following command:

dotnet new -t web 

Currently, the generated project includes .bowerrc and bower.json files. You can delete these since we'll be using NPM to install packages. If you don't have NodeJS installed on your system, make sure you do so before continuing.

The next thing we'll do is create a folder called Scripts in the root of your project. You'll find out why later on. Also add an empty webpack.config.js to the root of your project. As you might have guessed, this is the file we'll use to configure Webpack. Your project layout should look something like this.

Configuring Webpack

Before we start configuring Webpack, let's check out where our assets actually are. ASP.NET Core places all the files destined for the browser inside of the wwwroot folder by default. If you take a peep inside that folder, you'll see sub folders for your your JavaScript, CSS and image files. Note, the names of these sub folders aren't important. Feel free to rename them if you wish.

Personally, I prefer to reserve the wwwroot folder for the bundles that I want to provide to the browser. What we'll do is use the Scripts directory that was created earlier for the working files that will get included in the bundles.

Let's add two pretty trivial JavaScript files to our Scripts folder.

//other.js
function func() {
    alert('loaded!');
}
module.exports = func;

//main.js
var other = require('./other');

other();

Our scripts have been written using the CommonJS module syntax. The main.js file imports other.jsand calls the exported function. Ok, simple enough. Let's take a look at webpack.config.js.

var path = require('path');

module.exports = {
    entry: {
        main: './Scripts/main'
    },
    output: {
       publicPath: "/js/",
       path: path.join(__dirname, '/wwwroot/js/'),
       filename: 'main.build.js'
    }
};

The webpack.config.js file is a CommonJS module that we'll use to setup Webpack. The sample above shows a fairly bare bones Webpack configuration. Inside of entry, we define a main module and point it to the location of main.js file since that's where our app starts. The name of the bundle can be changed to something else if you like. There's no requirement for it to be called main. Inside of output, we let Webpack know what to name the bundle file and where to place it. The publicPath property configures the relative URL that the browser will use to reference our bundles.

Alright, that's good for now. Before we generate our bundle, make sure you have Webpack installed globally on your machine. Type the following command in your terminal. You'll only have to do this once.

npm i -g webpack 

Now we're ready to create our bundle. Make sure your terminal path is at the root of your project directory. Now run

webpack 

Your terminal output should look similar to below.

In your code editor, open Views/_Layout.cshtml. Near the bottom of the file, add a script reference to our bundle.

<script src="~/js/main.build.js"></script>

The generated ASP.NET Core template adds a few scripts tags wrapped in environment tag helpers. Go ahead and remove these for now.

<environment names="Development">
        <script src="~/lib/jquery/dist/jquery.js"></script>
        <script src="~/lib/bootstrap/dist/js/bootstrap.js"></script>
        <script src="~/js/site.js" asp-append-version="true"></script>
</environment>

Finally, we can run our application and see if our bundle works. Execute the following commands in the command terminal.

dotnet restore
dotnet run

Navigate to http://localhost:5000 in your browser. If everything works as expected, you should see an alert with loaded! in the browser window.

Tying the builds together

We can reduce the number of commands we have to type by leveraging the build events in project.json. Update the scripts section to include the precompile event. To see the other available events, head over to the .NET Core Tools docs.

"scripts": {
    "precompile": ["webpack"],
  },

Now running dotnet run or dotnet build will also run Webpack to generate the bundle.

Conclusion

In this post, we got a short introduction to setting up Webpack in ASP.NET Core. Webpack often gets labeled as overly complex and difficult to setup. Hopefully, this post showed you how easy it is to get started and made you a little more curious about what else it can do.



About HostForLIFE.eu

HostForLIFE.eu is European Windows Hosting Provider which focuses on Windows Platform only. We deliver on-demand hosting solutions including Shared hosting, Reseller Hosting, Cloud Hosting, Dedicated Servers, and IT as a Service for companies of all sizes.

We have offered the latest Windows 2016 Hosting, ASP.NET Core 2.2.1 Hosting, ASP.NET MVC 6 Hosting and SQL 2017 Hosting.


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