"Error occurred in deployment step 'Activate Features': Key cannot be null. Parameter name: key"

In this article you will see how to resolve the error “Error occurred in deployment step 'Activate Features': Key cannot be null. Parameter name: key” in Visual Studio 2010.


Error

I have created a custom Content Type using Visual Studio 2010. The entire solution looks like the following:












When I try to deploy the solution from Visual Studio 2010 by right-clicking on the solution and then click on Deploy, I was getting the error:

"Error occurred in deployment step 'Activate Features': Key cannot be null. Parameter name: key"

Reason

The reason is in the Content Type, the Elements.xml file <FieldRef> tag was closed as </FieldRef> which will be considered as an empty or null element.








How to Resolve

In the Conte