Question

I’m currently rewriting an older AddIn for Excel 2007 that another developer write about 2 years ago. But when I want to debug it in VS 2008, the following error occurs;

Error   1   The type or namespace name 'Extensions' does not exist in the namespace 'Microsoft.Office.Tools.Excel' (are you missing an assembly reference?) 6   36  E:\..\doc.cs

I have Offie 2007 installed, as well as Power tools and virtually any package I could find when searching the internet for this assembly. But nothing contained it.

So now I desperately ask for your help on where to get this assembly from…

Answer 1

Microsoft.Office.Tools.Excel.Extensions is from VSTO 2005 SE and doesn’t work in VSTO 3.0 or higher. If it’s not working in VS 2008, that means you have VSTO 3.0 installed and are targeting it.

• Solution: Make sure you have
  Visual Studio 2008 SP1 installed
  (yes, VS2008 SP1, not
  only .NET 3.5 SP1 or VSTO 3.0 SP1). This will fix the issue. Download here: Microsoft Visual Studio 2008 Service Pack 1 (Installer)