What does the .csproj file do?

Basically the .csproj file contains the list of files in your project, plus the references to system assemblies etc.

There are a whole bunch of settings - Visual Studio version, project type, Assembly name, Application Icon, Target Culture, Installation Url,...

Everything you need to build your project. While you could assume that you need everything in the current folder, having an explicit list allows you to organise them logically both on the disk and in the project so you can more easily find the files you want.

It's just XML so you can open it in your favourite text editor and take a look.

You get one .csproj file per assembly and the .sln (solution file) ties together all the assemblies that make up your project.

Taken from What is .csproj file?

".csproj" is a Visual Studio .NET C# Project file extension. This file will have information about the files included in that project, assemblies used in that project, project GUID and project version etc. This file is related to your project. It will be automatically generated when we create

".sln" is a structure for organizing projects in Visual Studio. It contains the state information for projects in .sln (text-based, shared) and .suo (binary, user-specific solution options) files. We can add multiple projects inside one solution.

The file contains a list of all the files to be compiled as part of the project, as well as other options like the project name, release and debug configurations, compilation options, and so on.

Updated for .NET 5

This is the most important file in our application. It tells .NET how to build the project.

All .NET projects list their dependencies in the .csproj file. If you have worked with JavaScript before, think of it like a package.json file. The difference is, instead of a JSON, this is an XML file. When you run dotnet restore, it uses this file to figure out which NuGet packages to download and copy to the project folder.

The .csproj file also contains all the information that .NET tooling needs to build the project. It includes the type of the project being built (console, web, desktop, etc.), the platform this project targets and any dependencies on other projects or 3rd party libraries.

Starting in .NET 5, there have been a few major changes to make this file easier to read and maintain, which are listed below.

• In the older versions of .NET, every file in the project had to be listed in the .csproj file. Now they are automatically included and compiled.**
• Previously, GUIDs were used everywhere. Now they are used rarely.
• The path to the DLL files was included, but starting .NET 5, you don't need to specify the path on the disk.

Example:

<!-- Sdk attribute specifies the type of project, which is web. -->
<Project Sdk="Microsoft.NET.Sdk.Web"> 

  <PropertyGroup>
    <!-- TargetFramework is the framework this project will be using, which in this case is .NET 5. -->
    <TargetFramework>net5.0</TargetFramework>
  </PropertyGroup>

  <ItemGroup>
    <!-- PackageReference references the NuGet packages. -->
    <PackageReference Include="Microsoft.AspNetCore.All" Version="2.0.0" />                                              
  </ItemGroup>

</Project>

Note: If you are using Visual Studio, this file will be hidden, but you can right-click on the project and choose edit the project file.