problem with custom serialization in .net 2.0

[C# Programming]

i'm trying to serialize and deserialize an object using xmlSerializer .the serialization part is ok ,but in the deserialization part i don't get "amount" calculated as expected.

following is the code of the object i serialize.


[Serializable]
public class _object
{
public int itemCnt;
public string itemName;
public decimal unitPrice;
[NonSerialized]public decimal amount;


public _object(int _itemCnt,string _itemName,decimal _unitPrice)
{
itemCnt = _itemCnt;
itemName = _itemName;
unitPrice = _unitPrice;
}

protected _object(SerializationInfo info, StreamingContext context)
{
itemCnt = info.GetInt32("itemCnt");
itemName = info.GetString("itemName");
unitPrice = info.GetDecimal("unitPrice");
amount = info.GetDecimal("total");
}

[SecurityPermissionAttribute(SecurityAction.Demand,SerializationFormatter = true)]
public virtual void GetObjectData(SerializationInfo info, StreamingContext context)
{
info.AddValue("itemCnt", itemCnt);
info.AddValue("itemName", itemName);
info.AddValue("unitPrice", unitPrice);
amount = itemCnt * unitPrice;
}

}

any idea why?