Set affected document dispositions all to N/A

I am trying to set all of the CN affected document dispositions to N/A when the action is "Revise". I get an error when checking the syntax that reads, "The method is not fully specified"

My item type name is a_CN_Affected_Item

I am adding the method under the Server Events tab, server-side, C#

if (this.getProperty("action") == "Revise" && this.getProperty("item_type") == "Document"){
return this;

Can you tell me what i have incorrect?