SharePoint custom workflow activity. “Failed to load toolbox item. It will be removed from toolbox.”

I was getting this error message in Visual Studio 2008 when adding a custom activity to an existing workflow.

Solution

This worked for me, your mileage, may and probably will vary.

It was necessary for me to un-gac the workflow project, then the custom activities could be added to the design surface as expected.

9 thoughts on “SharePoint custom workflow activity. “Failed to load toolbox item. It will be removed from toolbox.””

Maria says:

January 25, 2010 at 2:50 pm

Thank you! Saved me a lot of time!

robert says:

February 12, 2010 at 10:09 pm

Thank you so much! I’ve been banging my head about this for the whole day…
How can one develop for sharepoint then, since the workflow libraries go into GAC everytime you deploy?

Pankaj Bajpai says:

July 15, 2010 at 12:01 pm

Thanks a lot…

Jennifer says:

July 22, 2010 at 1:56 pm

Thank you very much!! I couldn’t figure out why I was getting this error. That solved the problem.

RB says:

August 30, 2010 at 3:11 pm

just close the visual studio and open again… worked for me

MB says:

January 8, 2015 at 6:52 pm

you saved my life. Thanks a lot.

Reply

maratgaleyev says:

July 23, 2011 at 1:07 pm

Thank you, sir!

Boris Gomiunik says:

September 13, 2012 at 12:06 pm

Crazyyyyy simple and logical. Thanks for sharing this.

Jacob Mathew says:

January 28, 2013 at 4:48 pm

thank for this it saved my time

Edward Wilde

Developer | Diver