Pipeline error "Key cannot be null - Parameter name: key"

I was going through the Microsoft BizTalk 2004 Unleashed book and came across an error when adding the pipelines.

Here were my steps:

1. Manually type an XML document
2. Use VS2005 to create a schema
3. Open the schema in VS BizTalk
4. Tried to compile:

Node "<Schema>" - Schema reference "" is not a valid reference or does not exist in the current project.

I continued on, create a pipeline and added a XML disassembler to it. When I clicked on the Document schemas property, the error "Key cannot be null, Parameter name: key". This error popped up on many other options.

I thought that the error message just meant that it didn't have a namespace. I added namespaces, changed Root references, blah blah... and hoped it would eventually clear up - in short - it didn't!

The problem was that the schema creator of VS2005 was not understood by BizTalk 2006. I re-created the Schema creating the layout by hand, compiled and it worked fine! Clicked the Document schemas, and away you go.

Morale: Don't ignore your compilation errors, even if they are cryptic :-)

Even if you do ignore them - you wouldn't get anywhere