string
The value to use in the Content-Type header, or null.
Returns the value to use in the Content-Type header for this form section.
If this property returns a non-null, non-empty string, then the returned string will be set as the Content-Type of this form section.
If this property returns null or an empty string, then the Content-Type header will be omitted from this form section. How the server will handle this data is left up to the individual server.