Unable to load referenced library The process cannot access the file because it is being used by another process.

Question

We are getting the error message noted in the subject line. It just started today.

Environment:

• OS - WinXP SP3 with all the latest updates.
• Visual Studio 2008 with all the latest updates.

Steps to recreate the problem:

1. Open Visual Studio and create a VB Class Library project. Add the following property and property method to Class1:

   Protected mProperty1 As String

   Public Property Property1() As String Get Return mProperty1 End Get Set(ByVal pProperty1 As String) mProperty1 = Left(pProperty1, 100) End Set End Property

2. Compile the project.

3. Open a second copy of Visual Studio and create a VB Windows Application project.

4. Add a reference to \Projects\ClassLibrary1\bin\debug\ClassLibrary1.dll

5. Compile the project.

6. Alt-tab to the Class Library project and change the Left(pProperty1, 100) to Left(pProperty1, 50).

7. Compile the project.

8. Alt-tab to the Windows Application project.

9. The error list shows two errors:

Error 1 Unable to load referenced library 'D:\Visual Studio 2008\Projects\ClassLibrary1\bin\Debug\ClassLibrary1.dll': The process cannot access the file because it is being used by another process.

Error 2 Unable to load referenced library 'D:\Visual Studio 2008\Projects\ClassLibrary1\bin\Debug\ClassLibrary1.dll': The process cannot access the file because it is being used by another process. D:\Visual Studio 2008\Projects\ClassLibrary1\bin\Debug\ClassLibrary1.dll

If I close the Windows Application project (leaving Visual Studio open) and re-open it, the error goes away and the project compiles.