Organizing .NET Projects With Solutions

Whenever you create a .NET application, one of the essential files created is the project file. In C#, it is named xxxx.csproj; in VB.NET, it is named xxxx.vbproj; and in F#, it is named xxxx.fsproj.

This file contains key information for the compiler:

Project type - executable, class library, etc
Referenced projects
Referenced nuget packages
Project metadata - assembly name, namespaces, etc.

Most of the time, this is sufficient.

But sometimes, you want to manage multiple projects as a unit. The solution helps in this scenario.

Let us start by creating an empty folder in which to store our code:

mkdir DotNetSolution

We then change into this directory and create a blank class library

dotnet new classlib -o Library

Next, we create a console application

dotnet new console -o ConsoleUI

Our folder structure now looks like this:

DirectoryStrucutre

If we wanted to build both of these, we would need to do it with two commands:

dotnet build Library/Library.csproj 

dotnet build ConsoleUI/ConsoleUI.csproj 

A solution can help in this situation.

The first step is to create a blank solution using the dotnet new sln command.

From within the current directory, type the following:

dotnet new sln

This solution will take the name of the current folder.

You can also change it to whatever you want using the -n switch

dotnet new sln -n WizardApp

The file structure is now as follows:

DirectoryStructureWithSolution

What is in the WizardApp.sln file? It is actually text and can be viewed as follows:

cat WizardApp.sln

This will return the following:

Microsoft Visual Studio Solution File, Format Version 12.00
# Visual Studio Version 17
VisualStudioVersion = 17.0.31903.59
MinimumVisualStudioVersion = 10.0.40219.1
Global
	GlobalSection(SolutionConfigurationPlatforms) = preSolution
		Debug|Any CPU = Debug|Any CPU
		Release|Any CPU = Release|Any CPU
	EndGlobalSection
	GlobalSection(SolutionProperties) = preSolution
		HideSolutionNode = FALSE
	EndGlobalSection
EndGlobal

Currently, it is essentially empty.

We need to add projects to the solution.

This is done using the dotnet sln add command, which takes a project file (csproj,vbproj or fsproj) as a parameter.

dotnet sln add Library/Library.csproj

This will print the following:

Project `Library/Library.csproj` added to the solution.

Similarly, for the console application:

dotnet sln add ConsoleUI/ConsoleUI.csproj

The following will be printed

Project `ConsoleUI/ConsoleUI.csproj` added to the solution.

Now, if we run dotnet build from the current directory:

SolutionBuild

We can see here that both of the projects were built successfully.

If we now examine the contents of the sln file:

Microsoft Visual Studio Solution File, Format Version 12.00
# Visual Studio Version 17
VisualStudioVersion = 17.0.31903.59
MinimumVisualStudioVersion = 10.0.40219.1
Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Library", "Library\Library.csproj", "{377BD026-7E71-47B4-BFFC-A5BA74C012EA}"
EndProject
Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "ConsoleUI", "ConsoleUI\ConsoleUI.csproj", "{F664F180-4385-4ABA-935C-DF24FA652B30}"
EndProject
Global
	GlobalSection(SolutionConfigurationPlatforms) = preSolution
		Debug|Any CPU = Debug|Any CPU
		Debug|x64 = Debug|x64
		Debug|x86 = Debug|x86
		Release|Any CPU = Release|Any CPU
		Release|x64 = Release|x64
		Release|x86 = Release|x86
	EndGlobalSection
	GlobalSection(ProjectConfigurationPlatforms) = postSolution
		{377BD026-7E71-47B4-BFFC-A5BA74C012EA}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
		{377BD026-7E71-47B4-BFFC-A5BA74C012EA}.Debug|Any CPU.Build.0 = Debug|Any CPU
		{377BD026-7E71-47B4-BFFC-A5BA74C012EA}.Debug|x64.ActiveCfg = Debug|Any CPU
		{377BD026-7E71-47B4-BFFC-A5BA74C012EA}.Debug|x64.Build.0 = Debug|Any CPU
		{377BD026-7E71-47B4-BFFC-A5BA74C012EA}.Debug|x86.ActiveCfg = Debug|Any CPU
		{377BD026-7E71-47B4-BFFC-A5BA74C012EA}.Debug|x86.Build.0 = Debug|Any CPU
		{377BD026-7E71-47B4-BFFC-A5BA74C012EA}.Release|Any CPU.ActiveCfg = Release|Any CPU
		{377BD026-7E71-47B4-BFFC-A5BA74C012EA}.Release|Any CPU.Build.0 = Release|Any CPU
		{377BD026-7E71-47B4-BFFC-A5BA74C012EA}.Release|x64.ActiveCfg = Release|Any CPU
		{377BD026-7E71-47B4-BFFC-A5BA74C012EA}.Release|x64.Build.0 = Release|Any CPU
		{377BD026-7E71-47B4-BFFC-A5BA74C012EA}.Release|x86.ActiveCfg = Release|Any CPU
		{377BD026-7E71-47B4-BFFC-A5BA74C012EA}.Release|x86.Build.0 = Release|Any CPU
		{F664F180-4385-4ABA-935C-DF24FA652B30}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
		{F664F180-4385-4ABA-935C-DF24FA652B30}.Debug|Any CPU.Build.0 = Debug|Any CPU
		{F664F180-4385-4ABA-935C-DF24FA652B30}.Debug|x64.ActiveCfg = Debug|Any CPU
		{F664F180-4385-4ABA-935C-DF24FA652B30}.Debug|x64.Build.0 = Debug|Any CPU
		{F664F180-4385-4ABA-935C-DF24FA652B30}.Debug|x86.ActiveCfg = Debug|Any CPU
		{F664F180-4385-4ABA-935C-DF24FA652B30}.Debug|x86.Build.0 = Debug|Any CPU
		{F664F180-4385-4ABA-935C-DF24FA652B30}.Release|Any CPU.ActiveCfg = Release|Any CPU
		{F664F180-4385-4ABA-935C-DF24FA652B30}.Release|Any CPU.Build.0 = Release|Any CPU
		{F664F180-4385-4ABA-935C-DF24FA652B30}.Release|x64.ActiveCfg = Release|Any CPU
		{F664F180-4385-4ABA-935C-DF24FA652B30}.Release|x64.Build.0 = Release|Any CPU
		{F664F180-4385-4ABA-935C-DF24FA652B30}.Release|x86.ActiveCfg = Release|Any CPU
		{F664F180-4385-4ABA-935C-DF24FA652B30}.Release|x86.Build.0 = Release|Any CPU
	EndGlobalSection
	GlobalSection(SolutionProperties) = preSolution
		HideSolutionNode = FALSE
	EndGlobalSection
EndGlobal

The magic is happening here, where each project is assigned a Guid that is used to set some build configurations.

SolutionStructure

Let us now create a new test project:

dotnet new xunit -o Tests

We then add this to the solution:

dotnet sln add Tests/Tests.csproj

We can now see our sln is updated.

Microsoft Visual Studio Solution File, Format Version 12.00
# Visual Studio Version 17
VisualStudioVersion = 17.0.31903.59
MinimumVisualStudioVersion = 10.0.40219.1
Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Library", "Library\Library.csproj", "{377BD026-7E71-47B4-BFFC-A5BA74C012EA}"
EndProject
Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "ConsoleUI", "ConsoleUI\ConsoleUI.csproj", "{F664F180-4385-4ABA-935C-DF24FA652B30}"
EndProject
Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Tests", "Tests\Tests.csproj", "{8D3A15BA-6953-4FB7-BF97-B90366B886E0}"
EndProject

-- The rest trimmed out

We can also remove projects from a solution, using the dotnet sln remove command

dotnet sln remove Tests/Tests.csproj

This will print the following:

Project `Tests/Tests.csproj` removed from the solution.

It is strongly discouraged to directly manipulate this file manually.

You can also list all the projects in a sln file

dotnet sln list

This will print the following:

Project(s)
----------
ConsoleUI/ConsoleUI.csproj
Library/Library.csproj

Finally, having more than one solution file for your own reasons is also possible. Perhaps one will include the test projects, and the other won’t.

In this scenario, pass the solution name as a parameter when building.

dotnet build WizardApp.sln

TLDR

When handling software projects with multiple projects, it is beneficial to organize them into solution (sln) files.

The code is in my GitHub.

Happy hacking!