ASP.NET core is a significant redesign of ASP.NET. ASP.NET core is an open source, cross platform framework for developing the cloud based Application like Web Application IoT Application and the mobile backend Application. It runs on both frameworks; .NET core and full .NET framework. We can develop and run the ASP.NET core Application on the multiple (cross) platform such as Windows, Mac OS, and Linux.
There are a number of changes with ASP.net core framework. ASP.NET Core is not based on "System.Web.dll". The "System.Web.dll" works only with Windows platform for taking certain advantages of Windows features. The removal of "System.Web.dll" makes ASP.NET Core distant from ASP.NET Web Forms. It is based on many small and distinct parts. The advantages of smaller apps are reduced servicing, improved performance and security. Visual Studio 2015 is downloading or importing dependency packages by using NPN, Bower, Grunt and Gulp.
Following are some improvements in ASP.NET Core:
- HTTP request pipeline is now light weight and modular.
- Built-in dependency injection support.
- Ready to integrate to modern client-side frameworks and development Workflows.
- Open source and community focused.
- Build and run cross-platform ASP.NET apps.
- Cloud-ready environment (based configuration).
The new ASP.NET Core framework will have backwards compatibility and be able to run on ASP.NET 4.6 libraries. Currently, Microsoft uses "CORE" terminology and discontinues the old numbering system. We can install .NET framework 4.6 and .NET Core on the same machine. Core has its own core libraries.
.NET Core has core CLR and lightweight .NET runtime, which provides some service, like memory management and garbage collection.
.NET Core is a light weight and a cross platform version of the .NET framework. It contains a subset of class libraries from full NET framework and it is designed to work with the multiple platforms. The .NET core does not contain any libraries, which are depending on windows platform like System.Windows, System.Drawing etc.
.NET core is design to with both core framework and full framework. It also runs on Roslyn and builds are completely dynamic.
![structure]()
ASP.NET Project Structure
.NET Core adds the new concepts of the project structure and it has replaced some legacy elements, found in the previous versions of ASP.NET projects. ASP.NET core runs with the essential components, required to start the Server and serve simple pages. We can add more components in the project, as per the requirement. ASP.NET Core contains built-in IoC (inversion of control) Container, which is used to configure the dependencies. When we create ASP.NET Core project using VS 2015, it looks, as shown below:
![structure]()
As shown in the above image, the new structure includes a "Solution Items" folder and this folder contains a file called "global.json" and our Web project is created within "src" folder within the solution.
Solution contains following files/folders
- global.json
This file is present at the root level directory of the Application and contains solution level settings. Generally, it contains the name of the project and SDK version. The settings under this file are used for all the projects, under the solution.
- wwwroot
This folder contains the static assets like JavaScript, CSS, images, required by the project.
- Dependencies
In this tab, we can add or remove Project Dependencies.
- project.json
This is the replacement of Web.config and pacage.config file. It is in JSON format. This file contains information like the version of .NET Core framework, Compilation options, framework details, dependencies, script for installing front-end dependencies, using NPM, bower or other package managers.
- bower.json and package.json
The bower.json file contains a list of bower dependencies and package.json file contains a list of NPM dependencies to be used in the project. By default, these files are not visible in the project.
- gulpfile.js
This file contains a set of gulp tasks to combine, minify, copy the front-end files and dependencies and the tasks are executed, using a command line. We can also configure to run this command during the build process.
- appsettings.json
This file contains the Application level settings like a database connection string and other custom Application settings. This file is read by the Application in startup.cs file.
- Startup.cs
This is a starting point of the ASP.NET Core Application. This is very similar to OWIN Katana project. This file has static void main method, which is a starting point of the Application. Generally, this static method is used to load the middleware services, configure abstract etc.
- References
This folder details the Server-side references for the project. This is very similar to the previous version of ASP.NET.
Support for Dynamic Compilation
Roslyn (new compiler) supports a dynamic compilation. It enables us to change the code of controller, classes, views etc. The runtime and the compiler will automatically build the Application. The dynamic compilation enables us to run the Application, using Ctrl + F5 and makes a change to the file, save it and refresh, and the application's new changes are immediately in effect. The dynamic compilation feature is working with Visual Studio as well as any code editor.
Open source
.NET Core is now open source and many components have already been made available on GitHub. This includes Roslyn compiler, ASP.NET and Core CLR.
Conclusion
There are many changes introduced in the ASP.NET Core. With this release, it is possible to work outside Visual Studio. We can also download the dependency, using NPN, Bower, Grunt, and Gulp. The Application developed with older framework versions (4.5.2 or previous) works with full .NET runtime (these will not run on core CLR).