GridView's UpdateCommand throws the error "Procedure or function editArea has too many arguments specified" even though the exact input and ouput parameters are specified in the UpdateParameters section of the SqlDataSource.
Removing output parameters from the UpdateParameters list results in the following error: Procedure or function 'xxx' expects parameter '@xxx', which was not supplied.
Follow these steps:
*** Note: The parameters in the Parameters list do not need the @; leave the names as they appear. However in the Command text, use the same name, but add @.
The SqlDataSource should look similar to this: