Set dispositions to "N/A" on all affected documents with action set to "Revise"

I added this method under the "Server Events" tab, client-side, C# but it does not work. What is incorrect?

if (this.getProperty("action") == "Revise" && this.getProperty("item_type") == "Document") {
    this.setProperty("dispo_assemble","N/A");
    this.setProperty("dispo_repairs","N/A");
    this.setProperty("dispo_stock_kit","N/A");
    this.setProperty("dispo_supplier_stock","N/A");
    this.setProperty("dispo_wip","N/A");    
}
return this;