Solve The Error “a project with an output type of class library cannot be started directly”

C-sharp, commonly known as C#, is a Microsoft developed programing language that works on the .Net framework. With C#, programmers all over the world develop desktop applications, web applications, mobile apps, console applications, and many more. This language has given a lot of liberty to the programmers to design the application just the way they are planning. And, that’s the reason even newbies are learning this language to design marvelous applications and set a foot in the programming world. When working on C#, you may encounter many errors, and “a project with an output type of class library cannot be started directly” is one of those.

We are going to discuss this error in this post, so you don’t need to get worried. You just need to go ahead with the article to resolve the error.

How do you get the error warning?

You land up in the error when you try to debug the project to understand how the algorithm implementation works for you. When you download the project, the folder contains the .sln file and .csproj file (inside a folder with source files).

Till here, there is no issue detected. When you downloaded Visual Studio to open the .sln file, you can have success till here, but as soon as you debug, you get the error warning. Take a look at the error that shows up

A project with an Output type of Class Library cannot be started directly In order to debug this project, add an executable project to this solution which references the library project. Set the executable project as the startup project.

Now that you know how you get into trouble, let’s figure out the solutions to fix it

Solutions to Fix “a project with an output type of class library cannot be started directly”

There are a few highly effective solutions that can help you solve the error in a simpler way. Have a look

Solution 1 – Add a new project with output type

The installed project compiles into a dll assembly along with providing a set of classes with the functionality implemented. A new project needs to be added with the output type of either windows application or console application. Perform a test by implementing logic on your class library of the newly added project.

Once you find the output type of the project, you can change it with the help of the following way

  • In Solution Explorer, right-click on the project, and it opens Properties
  • Open the Properties tab and choose Application. There is ComboBox that is marked with Output Type. 

Solution 2 – Select the correct Project

If you have multiple projects, you need to make sure which project you have opened. You need to open the correct one set as ‘Start Project’ instead of any class library projects. For this, you can try the below steps

  • Tap right-click on the Solution Explorer
  • Select the Properties
  • You need to expand the Common properties tab and select Start Up Project
  • Tap the radio button named Single Start_up project
  • You need to select the Project name
  • In the end, debug the project


The solutions discussed are effective to handle the exception “a project with an output type of class library cannot be started directly”. I hope you can get rid of the error warning. I wish you luck!

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