c# - Partial Class Instance Initialization Null Reference Exception -

i have service reference code below:

[system.xml.serialization.soaptypeattribute(namespace="urn:customer")] public partial class receipt : object, system.componentmodel.inotifypropertychanged {      private int counternofield;      private double activekwhfield;       /// <remarks/>     [system.xml.serialization.soapelementattribute("counter-no")]     public int counterno {         {             return this.counternofield;         }         set {             this.counternofield = value;             this.raisepropertychanged("counterno");         }     }      /// <remarks/>     [system.xml.serialization.soapelementattribute("active-km")]     public double activekm {         {             return this.activekm field;         }         set {             this.activekmfield = value;             this.raisepropertychanged("activekm");         }     }      public event system.componentmodel.propertychangedeventhandler propertychanged;      protected void raisepropertychanged(string propertyname) {         system.componentmodel.propertychangedeventhandler propertychanged = this.propertychanged;         if ((propertychanged != null)) {             propertychanged(this, new system.componentmodel.propertychangedeventargs(propertyname));         }     } } [system.xml.serialization.soaptypeattribute(namespace="urn:customer")] public partial class arrayofreceipt : object, system.componentmodel.inotifypropertychanged {      private receipt[] itemfield;      /// <remarks/>     public receipt[] item {         {             return this.itemfield;         }         set {             this.itemfield = value;             this.raisepropertychanged("item");         }     }      public event system.componentmodel.propertychangedeventhandler propertychanged;      protected void raisepropertychanged(string propertyname) {         system.componentmodel.propertychangedeventhandler propertychanged = this.propertychanged;         if ((propertychanged != null)) {             propertychanged(this, new system.componentmodel.propertychangedeventargs(propertyname));         }     } } 

and, when want create instance of "arrayofreceipt" or set value, or access it, encounter same problem: system.nullreferenceexception. code when try create:

var prev_cons = new myservice.receipt(); prev_cons.counterno = 1; prev_cons.activekm = 3265; myservice.arrayofreceipt prev_consarr = new myservice.arrayofreceipt(); prev_consarr.item.setvalue(prev_cons, 0); 

unfortunatelly, prev_consarr.item null, , cannot initialize it. please show me way initialize , set value object. in advance.

the way code written, can initialize prev_consarr.item this:

prev_consarr.item = new receipt[3]; 

that create new arrayofreceipt hold 3 receipt objects. create constructor arrayofreceipt class initializes item. either of these methods eliminate nullreferenceexception

looking @ way using arrayofreceipt class, may want consider changing type of item list<receipt>. make easier change number of receipt classes storing.

depending on trying do, may want create addreceipt method in arrayofreceipts , move yourpropertychanged event method. right now, propertychanged event fire when arrayofreceipts class overwrites array of receipts.