A project with output type of class library cannot be started directly - with a startup exe

Question

Firstly I\'m completely aware of this message and why it happens normally. It\'s not that I\'m just trying to run a dll (like this question).

I have a project that c

Answer 1

I had this problem with projects that were created as "Windows Control Library" that somehow forget their status. Unloading and reloading the project usually did the trick.

If it was created as a "Class Library" then to make it a "Windows Control Library" I manually add the following to the .csproj file. It was the only difference I could see between a class library and windows control library project.

BTW - starting a Windows Control Library starts the User Control Test Container - allows you to test any user control in the library. Very cool.

<Service Include="{94E38DFF-614B-4cbd-B67C-F211BB35CE8B}" />

add that inside of an <itemgroup> element.

Answer 2

Going to resurrect this thread, I have just been experiencing similar issues, when right clicking a project and start new instance..

So instead of right clicking the project and selecting start new instance, I right clicked and clicked set as startup project.

Low and behold a class library project was set to bold, certainly not the one I was right clicking.

I tried selecting a different executable project and setting that as the startup project. Same class library was highlighted as the start up project.

Realised that the current open file was from that project, possibly all the open files were from that project...

closed all open files and tried again.... Problem solved, behaviour as expected for both set as start up project and start new instance options...

Definitely a bug, hope this helps others..

• Microsoft Visual Studio 2010 Version 10.0.40219.1 SP1Rel
• Microsoft .NET Framework Version 4.0.30319 SP1Rel

Answer 3

Typically problems in VS are caused by:

• Add-ins: Run VS without and see if the problems is solved
• Corrupted files in your solution: Delete / rename all files created by Visual Studio which are not part of your project, i.e. all .suo, .ncb files and a like.

Answer 4

This sounds like a transient Visual Studio problem. Reinstallation or upgrade may solve your problem.

Answer 5

If you plan to use/create/add extra dll's or just have more than one project in your solution, you may get this kind of problem, especially if you forgot a simple rule: 1. In your "Solution Explorer" window. Right click and chose "Set StartUp Projects..." 2. Under "Start Up Project" select and change "Single startup project" to your working entity.

Answer 6

Another colleague suggested it's because after clicking Debug > Start new instance, while I'm waiting for it to start up, I click on a different project. I don't do it for any reason, just randomly selecting things as I wait for the project to start up. Maybe Visual Studio looks at the selected project sometime after I clicked the menu, gets confused, and shows the error message?

Anyone able to confirm this matches their experience?