How to create a Custom Subject with a VF E-Mail Template?

Question

I am trying to create the custom Subject in a VF Email Template, as follows

Subject - Case Descrition - {!Case.Description}

When I was using the above code while creating it

The HTML Email Content specified in Step 3 is not valid. Please go back 
to Step 3 and correct the following problem: Unknown property
'core.email.template.EmailTemplateComponentController.Case'

In the HTML Email Case why can we use Subject Case Description - {!Case.Description}, but not in a VF Email Template?

Answer 1

You should define the subject inside a messaging:emailTemplate tag.

<messaging:emailTemplate subject="Case Description - {!relatedTo.Description}"
recipientType="User" 
relatedToType="Case">

and put your dummy subject in that screen. Do not use the merge fields which you are currently using.