Purpose of the .csproj File in .NET

July 6, 2021   • dotnet

The project file, i.e. the file with the .csproj extension tells dotnet how to build the ASP.NET application. It’s one of the most important files in an ASP.NET project. If you are familiar with Node.js, think of a project file as a package.json file.

An ASP.NET project can depend on third-party libraries developed by other developers. Usually, these libraries are installed as Nuget packages using Nuget package manager. Once you install a package using Nuget, the name of the package along with its version is listed in the project file.

Upon running the ‘dotnet restore’ command, dotnet uses the project file to determine the packages to install from Nuget.

To compile an ASP.NET application, the compiler needs information such as the version of the dotnet framework, the type of the application, etc. A project file stores all this information that allows dotnet to build and compile the project.

Consider the following example of a project file that contains the various Nuget packages that an ASP.NET application depends on, along with other information dotnet tooling needs to build the application.

<?xml version="1.0" encoding="UTF-8"?>
<Project Sdk="Microsoft.NET.Sdk.Web">
      <PackageReference Include="SQLite" Version="3.13.0" />
      <PackageReference Include="Microsoft.Data.Sqlite.Core" Version="6.0.0-preview.4.21253.1" />
      <PackageReference Include="Microsoft.Extensions.Primitives" Version="6.0.0-preview.4.21253.7" />
      <PackageReference Include="Newtonsoft.Json" Version="13.0.1" />
      <PackageReference Include="log4net" Version="2.0.12" />

In this example, the file tells dotnet that it’s a web application that depends on .NET 5 framework. It also lists various dependencies such as SQLite and logfornet that the application depends upon.

Here are some of the benefits of the project file in ASP.NET Core vs. the older versions of ASP.NET:

  1. Automatic file includes: In older versions of ASP.NET, the project file contained a listing for every file in the project. Now, the files are automatically included.
  2. No GUIDs: Previously, the project file contained many GUIDs. Now they are rarely used.
  3. No DLL paths: Previously you had to include the path to the Nuget .DLL files that your project depended on. The new version allows you to directly refer to the Nuget packages without having to specify the path on the disk.