Fix: A project with an Output type of Class Library cannot be started directly

April 27, 2009 .NET, Development 13

You will sometimes come across the following error in a message box if you execute an ASP.NET application using Visual Studio 2005/2008

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. 

Resolution

In order to fix the above error, right click the Solution name in Visual Studio 2005/2008 and select Set as StartUp Project option from the popup menu.

Applicability

Visual Studio 2005
Visual Studio 2008

Anand Narayanaswamy
Anand Narayanaswamy is the editor-in-chief of Learnxpress. He was a Microsoft Most Valuable Professional (MVP) for a period of 9 years. He is a ASPInsider based in Trivandrum, Kerala State, India. Anand is the author of Community Server Quickly published by Packt Publishing.

13 Comments

  1. Yoav

    Thank you so much!

    July 27, 2009
  3. Bobby

    Thank you, it worked!!

    March 6, 2010
  4. Alex

    Thank You!

    March 12, 2010
  5. Salim

    Thanks alot dear!!!
    IT WORKED

    March 16, 2010
  6. Babak

    It did not work. This has worked for me in the past, but not this time. I have r-clicked on default.aspx, I have chosen it as the startup page, and I have default.aspx open as I hit the debug button.

    April 7, 2010
  7. Mariner Eccles

    This did not work for me. What I did was I took a project written on VS2008, converted it to VS2010, and got the error on debugging. When I attempted the resolution, I still got the error. So how would this work in VS2010, or can VS2008 projects that get converted to VS2010 lose debug cappabilities?

    Thanks.

    September 20, 2010
  8. DLeh

    Works in vs2010 too, for reference.

    January 14, 2011
  9. Euclides Marques

    Thanks !!!

    January 26, 2011
  10. KONAH

    THANKS!it works!!

    June 3, 2011
  11. SMR

    thanks alot…

    July 11, 2011
  12. Swetha

    Thanks a ton, it solved one of my big problem in running the code and debuggin it !!!

    September 12, 2011
  13. Rubi86

    Thankyou. It Works!

    September 23, 2011
  14. koajca

    Thank you! 😀
    It workds!

    January 3, 2012

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