• What's changed with new command in .NET Core 2.0

    Microsoft has released a major revision to the .NET Core framework around mid of August bumping the version to 2.0. This release includes not only the upgrade to the core framework but also include ASP.NET Core 2.0 and Entity Framework 2.0. Also along with this .NET Standard 2.0 is also released and it's now supporting around 32K + APIs and is a huge leap from what we had until now. You can read more about it by going to the announcement here.

    One of the changes among these is that the dotnet restore is now an implicit command which means that there is no need to execute the restore command explicitly for commands which needed to do a restore before executing it. 

    For example in .NET Core 1.1 whenever we executed a dotnet new command for creating a project we needed to execute the restore command before doing a build or execution. With .NET Core 2.0 when we execute the new command, the restore is now run automatically as part of the tooling. The following are the list of the commands which have got implicit support for restoration.


    Categories: ASP.NET Core

  • Override Default port and Host Name Used By ASP.NET Core Toolset

    .NET Core is the brand new modular framework from Microsoft for creating a wide variety of applications targeting Windows, Web, Cloud, IoT devices etc. Along with that they have introduced a cross platform toolchain for the command line which will help you to create and execute .NET core apps from the command line. 

    So for creating a normal web app in the .NET Core we will execute the following command.

    > dotnet run -t Web

    Then you will restore the packages by executing the command given below

    > dotnet restore

    After that you will execute the run command to build and host the application locally

    > dotnet run

    When this command is executed, it will first compile the application and upon successful build it will then host it using the built-in web server named Kestrel. Kestrel will use the port number 5000 by default for listening the requests for your app.

    From the screenshot you can see that the app is using port #5000 and is binded to localhost. This will be perfectly ok in a Dev enviroment since the developer will creating the application and is hosting it in the same machine. But this won't work in a production environment, where the requests to our app will be coming to the server from different machines out in the wild. That means, if you try to access the site using the ip address of the machine instead of localhost you will get a 404 error.

    Categories: ASP.NET Core

  • Compile a ASP.NET Core Web App on the fly using dotnet watch command

    One of the mostly used feature in Visual Studio while developing ASP.NET web applications is the ablity to make changes on the fly in the source code and able to see the changes in the browser without doing a compilation process manually. Actually Visual Studio tracks the changes made in the code and when you save the modifications, VS will automatically compile the changes in the background and restrats the session.

    In the .NET Core world, most of the development is happening with code editors such as Notepad, Visual Studio Code etc. These are vanilla text editors and lacks most of the features found in Visual Studio. So .NET Core team has created a command line tool called dotnet watch to achieve this ability for .NET Core. It's basically a file watcher which restarts the specified application whenever there is change is made in the source code. You can read more about it in the documentation hosted in GitHub.

    To add this functionlity in your code, you need to add the reference in the tools section in the project.json file as shown below.

    "tools": {
        "Microsoft.DotNet.Watcher.Tools": "1.0.0-preview2-final"  

    After adding the entry in the tools, you needs to restore the package using the dotnet restore command to get all the required files for the watch tool.


    dotnet watch <dotnet arguments>

    The watch tool can be used to compile, run application or test and publish whenever there is a change in the source code. So the <dotnet arugments> can be compile, run, publish etc. For the run command the usage is as shown below


    dotnet watch run

    Now, if you make any changes in server side code, the application will be automatically compiled and the reflected changes can be seen by just refreshing the browser.  In the following animation, if you look closely in the Terminal Window you can see that the application is stopped and compiled automatically when the source code is saved after making the changes.

    So using this tool, whenever we need to make change in the source code there is no need to stop the running instance and executing the dotnet run command again. Similary it can be used along with any other dotnet command as discussed in the post here in the documentation.

    Categories: DotNet CLI, ASP.NET Core

  • Deploying an Optimized Image of your ASP.NET Core MVC Web App in Docker

    In one of the posts I authored in the blog, I have shown you how to deploy an ASP.NET Core Web application in a Docker container, but the approach in the post has got a significant disadvantage. In that approach we always copied the entire contents of the directory which included all the static files, source code files etc, then restores all the packages inside the container and builds the application before it’s hosted in the container. This increases the boot up time of the container as well as the file size of the container.

    In this post, I will show you how to publish a web application into the container rather than copying all the files into container and then build the application inside that. I am going to create an .NET Core MVC web application using the dotnet new command, you can read more about that my post here.

    Step 1 : Create Project

    dotnet new –t web

    Step 2 : Restore Packages

    dotnet restore //restores all the packages referenced in the project.json files

    Step 3 : Publish Project

    dotnet publish –c Release –o publish

    Publishes the output of the project to the publish folder using the Release configuration. Before running the command make sure that node, bower and gulp is installed in your machine otherwise the publish command will fail

    If you look inside the publish folder you will find that it has copied all our static files and resources along with the dlls of our application and the dependencies used in it

    Categories: DotNet CLI, ASP.NET Core, Docker, MVC

  • Scaffolding an ASP.NET Core MVC application using dotnet command

    We all know that the dotnet new command will create a new console project containing a two files Program.cs and project.json out of the box for you

    dotnet new

    dotnet new console app


    dotnet new console app directory

    It was of great help in getting started with a console application in .NET Core, but this command was missing a more important feature – the ability to create a ASP.NET Core Web project from the command line. So, we developers relied on scaffolding tools such as yeoman to generate Web/MVC/Web API projects targeting .NET Core. So whenever the .NET team made changes to the framework and tools, we faced some incompatibilities. Either we needed to wait till the template is upgraded to support the new changes or needed to manually update the files after the project is created.

    This is now a thing of the past with the latest update to the .NET Core project implementing to facility to scaffold an MVC project targeting the Core  framework.


    dotnet new –t web


    dotnet new mvc project

    dotnet new mvc project directory

    The process of building and running the web project remains the same by using the following statements

    dotnet restore //restores the referenced packages
    dotnet run //compiles the project if it’s not and then hosts the application in the default port 5000

    dotnet restore mvc core app

    dotnet run web app

    web app in browser

    Categories: DotNet CLI, ASP.NET Core

  • Consuming Rest API methods in .NET Core MVC application

    Up until we need to rely on third party libraries for consuming a Web API in .NET Core applications. Even though Microsoft has got the Microsoft.AspNet.WebApi.Client library that can be used for consuming API methods, the support for .NET Core was not there until now. This library had a dependency on Microsoft.Net.Http library which was not supported in .NET Core. So with the release of the 5.2.3 version of Microsoft.AspNet.WebApi.Client they have fixed this issue and now it's available for you to use in .NET Core web applications too.

    Step 1 : Add reference in project.json

    You need to add following entries under dependencies section in the project.json file as given below.

    The Microsoft.AspNet.WebApi.Client is dependent on System.Net.Http and System.Runtime.Serialization.Xml libraries and that's why we need to add the above ones in the json file

    Step 2 : Use HttpClient to consume API

    We will use an object of the HttpClient class in the System.Net.Http namespace which was rebuilt for supporting .NET Core in latest version to invoke a connection to the service and for consuming the method. Then we will the base address and request headers using the BaseAddress and DefaultRequestHeaders methods respectively. To consume the web method, we will use the GetAysnc method which returns a resposne stream object containing the response from the Web API and by using the ReadAsAsync to read the result from the stream

    For other operations such as Post, Put and Delete we can use PostAsAsync, PutAsJsonAsync, DeleteAsync

    For more please refer here: http://www.asp.net/web-api/overview/advanced/calling-a-web-api-from-a-net-client

    Categories: ASP.NET Core, MVC

  • Using Nginx as a Reverse Proxy for ASP.NET Core Web App in Docker

    One of the main features of .NET Core framework is the ability to run the applications on variety of environments such as Linux, MacOS etc. It includes a light weight server known as Kestrel which is used to run web apps targeting the .NET Core framework. But one of the main disadvantage of Kestrel is that it is primarily a development server and is not recommended for production environments. We always used IIS as server for hosting .NET Web app, but in the case of .NET Core since it's cross platform and we can't rely on IIS for platforms other than Windows. In the case of Linux, Nginx is one of the most popular web server out there and is very good at serving static content. But, for the example in this post we are going to make use of the reverse proxy(passing requests to other servers) feature in Nginx to serve our core web app from a docker container running on a Linux distro.

    I had already written a post about the on how to get started with Nginx and I recommend you to go through the post here if you are working with Nginx for the first time. In this post, I am going to host a .NET Core web app in a Docker container using Nginx and Kestrel to serve the site on a Linux machine.

    Before I get started with coding, here's a little advice for all you guys. It is always a recommended thing to follow a proper structure for your source files in your project. In this case, I have created two folders, one for putting all the files related to .NET and one for putting all those related to Nginx as shown in the screenshot below.

    Step 1 : Create .NET Core App

    Create a sample mvc core application under the dotnet folder. I created this one using the boiler plate template provided by yeoman which generated all the folders and files showed in the above image. If you run the application now using the dotnet run command, it will host the application in Kestrel and can be accessed by using the url http://localhost:5000. I have modified the sample page to show the name of the server using the below code.

    Served By : @System.Environment.MachineName 

    Since I'm running it from the local machine, the page will show the name of my local box as the server name as shown in the image below.

    Since we are going to host our application inside the Docker container, let's create a docker file which contains some instructions to Docker to set up the container. It basically tells which base image should be used, copies the files from the current folder to a folder called app inside the container and sets it's as the working directory. Then it executes two dotnet commands to restore the packages first and then executes the build. Once the build is completed it exposes the port #8018 for serving the app from the container. The ENTRYPOINT command is used execute the application when we start the container and in our case it will execute the run command to host the application.

    Categories: Ubuntu, Web Developement, ASP.NET Core, Docker, nginx

  • Bundling & Minification in ASP.NET Core MVC Application

    Bundling is the process of concatnating a set of files into one single file and Minification is removing all the whitespaces and comments in the code, removing extra statements to make the file smaller in size. By doing bundling and minification in our application will reduced the request payloads as well as the number of requests to the server for downloading the assets such as CSS and JS files.

    .NET Framework had an in-built bundling and minification feature for sometime and since the advent of .NET Core they moved to use Grunt and Gulp for doing the same in both the RC versions. These tools primarily used JavaScript for operations such as file manipulation, automation, bundling and minification. Using these tools, we can also schedule tasks to run during a build or a publish event and is very useful in setting up a workflow for these opertions. The only downfall of these were we need to have some knowledge of programming in JavaScript and if you are not a fan of JavaScript then you will have some difficulties playing with it.

    So Mads Kristensen created an extension which automates these processes and the functionality can be achieved with no code. So when Microsoft released .NET Core 1.0 they integrated this into the ASP.NET Core Web project template and is now available for you out of the box, if you are using Visual Studio 2015 for your developement. Basically it supports

    • Bundling your assets into a single file
    • Minification of your assets
    • Create triggers for doing re-bundling automatically
    • Globbing patterns
    • MSBuild support

    Also the same is available as a NuGet package so that non Visual Studio users will also be able to use that in their projects. In this post, I am going to show how to do this a ASP.NET Core MVC project using Visual Studio Code and .NET CLI tools.

    Adding Reference & Configuring BundlerMinifier

    The first is to add the BundlerMinifier package in your json file as shown below

    tools": {
        "BundlerMinifier.Core": "2.0.238",
        "Microsoft.AspNetCore.Razor.Tools": "1.0.0-preview2-final",
        "Microsoft.AspNetCore.Server.IISIntegration.Tools": "1.0.0-preview2-final"

    Now we need to add a configuration file in which we will specifiy the files that needs to be bundled and minified. The default name for the config file is bundleconfig.json, the advantage being that the tool will take it automatically by the bundle command. If we specify a different filename, then we need to set it explicitly while executing the command for bundling.

    As you can see from the above snippet, we can specify multiple files that needed to be bundled into a single file as input and when the bundling operation is completed the unified file will be named using the value set in the outputFileName property. To minify the files, just set the value as true for the enabled property in the minify element.

    Categories: DotNet CLI, Visual Studio Code, ASP.NET Core

  • Logging into Console in ASP.NET Core MVC Application

    One of the important upgrades happened in .NET Core is the complete rewrite of the diagnostic logging pipeline which emits different events for logging errors. .NET Core now supports logging framework out of the box and also supports extensibility to make use of third party logging frameworks such as Log4Net, NLog etc. Logging can be implemented in quick time with a minimal amount of code in your application.

    Microsoft uses Microsoft.Extensions.Logging namespace for implement logging functionality and acts a wrapper for third party logging frameworks. This eradicates the need of writing our own logging framework to provide abstraction for third party frameworks such NLog, Log4Net etc. Also it has got inbuilt providers for supporting logging into Console, Event log, Trace Logging etc.

    Console logging in ASP.NET Core MVC application.

    As I said earlier logging has got inbuilt support provided by the ILogger class in .NET Core. For that, first we need to add a reference to the Microsoft.Extensions.Logging package in project.json file. Add the following entries under dependencies section in the json file for implementing providers for console and debug logging. 

    "Microsoft.Extensions.Logging": "1.0.0-rc2-final",
    "Microsoft.Extensions.Logging.Console": "1.0.0-rc2-final",
    "Microsoft.Extensions.Logging.Debug": "1.0.0-rc2-final",

    Categories: DotNet CLI, Visual Studio Code, ASP.NET Core

  • Custom Error Pages in ASP.NET Core MVC Application Using StatusCodePages Middleware

    While developing a web application, one of the best practice every developer should follow is to set up a custom error page for the site. Showing that dreaded yellow page to the user during the occurance of an exception is highly unprofessional and is prone to security risks. In one of the earlier post in the blog, I have explained the use of StatusCodePages middleware and various approaches for implementing it in a ASP.NET Core web application.

    In this post, I am going to implement custom error handling in an ASP.NET Core MVC application using the StatusCodePages Middleware. I will use the UseStatusCodePagesWithReExecute method provided by the middleware for showing the error the page in the case of an error. So let's add the following line in the Configure method in the Startup.cs file as shown below


    This method is telling the web server to execute the action method name Index in the ErrorController. Since we are using the ReExecute method the redirection will happen in the server itself thereby avoiding a round trip between the server and the client.

    Now, we need to create the controller and the action method in it. Create a file in the Controller folder, save it as ErrorController.cs and add the following lines in it

    Categories: DotNet CLI, Visual Studio Code, ASP.NET Core

  • Hosting ASP.NET Core Web App in Docker and Accessing it from outside

    In one of the earlier posts here, I have explained the steps needed to deploy a console application created in your local machine into a docker container. Today, I am going to go through the various steps needed for deploying a .NET Core web app into a Docker container using a dockerfile.

    Please refer the links given towards the bottom of the post to know more about Docker for Windows and .NET Core Apps.

    Creating the Project.

    In this post, I am going to use Yeoman for scaffolding a ASP.NET Core web app from the command prompt. You can read more about Yeoman and how to set it up in machine by referring the links given below.

    Getting Started With Yeoman
    Scaffolding Using Yeoman

    The command used for scaffolding a ASP.NET Core web app is

    yo aspnet

    When this command is executed, Yeoman will list the available options as shown in the image below.

    Categories: DotNet CLI, ASP.NET Core, Docker

  • Using StatusCodePages middleware in ASP.NET Core Application

    In ASP.NET Web and MVC applications, we have a customErrors.Mode property in the web.config file to specify custom error pages for exceptions happening in the application.

    In an ASP.NET Core web application we can make use of the UseStatusPages middleware to return a custom error page or a error message to the output stream. The middleware can be used to return a custom error message or page when there is an invlid response code between 400 and 600. Normally, the 4xx error is used for client errors where as 5xx is used for server errors.

    To explain the various options available in the middleware, I am going to use a ASP.NET Core web application created using Visual Studio Code and .NET CLI tools to run the application. You can also do the same using Visual Studio IDE too.

    Let's create a empty MVC project and run the application using the dotnet run command. It will self host the application and exposes port# 5000 for accessing the site. Open the site in the default browser by typing in http://localhost:5000/ and if you try to access a page which doesn't exists in the project, the browser will show an empty page or a page with a message saying that Page not found. Given below is the screenshot of the page I got in Chrome. If you open up the developer tools by pressing F12, you can see that the response from the server has 404 as status code.

    Categories: DotNet CLI, Visual Studio Code, ASP.NET Core