If you are building a WCF Workflow Service in Visual Studio 2010 the build may fail with one of two errors if there is a ; (semicolon) character in the path.

The error that you get may be one of the following:

Unable to delete file "C:\WFProjects\Valid;Path\WorkflowConsoleApplication1\DeclarativeServiceLibrary1\obj\Debug\DeclarativeServiceLibrary1.dll". Access to the path 'C:\WFProjects\Valid;Path\WorkflowConsoleApplication1\DeclarativeServiceLibrary1\obj\Debug\DeclarativeServiceLibrary1.dll' is denied.

Could not write to output file 'C:\WFProjects\Valid;Path\WorkflowConsoleApplication1\DeclarativeServiceLibrary1\obj\Debug\DeclarativeServiceLibrary1.dll' -- 'The process cannot access the file because it is being used by another process. '

To resolve this error, close all workflow designer windows in the project and rebuild.