Serializing a Nullable<DateTime> in to XML

Question

I am trying to serialize a class several of the data-members are Nullable objects, here is a example

[XmlAttribute("AccountExpirationDate")] public Nullable<DateTime> AccountExpirationDate  {    get { return userPrincipal.AccountExpirationDate; }    set { userPrincipal.AccountExpirationDate = value; }  } 

However at runtime I get the error

Cannot serialize member 'AccountExpirationDate' of type System.Nullable`1[System.DateTime]. XmlAttribute/XmlText cannot be used to encode complex types.

However I checked and Nullable is a SerializableAttribute. What am I doing wrong?

Answer 1

If you just want it to work, then perhaps:

using System; using System.ComponentModel; using System.Xml.Serialization; public class Account {     // your main property; TODO: your version     [XmlIgnore]     public Nullable<DateTime> AccountExpirationDate {get;set;}      // this is a shim property that we use to provide the serialization     [XmlAttribute("AccountExpirationDate")]     [Browsable(false), EditorBrowsable(EditorBrowsableState.Never)]     public DateTime AccountExpirationDateSerialized     {         get {return AccountExpirationDate.Value;}         set {AccountExpirationDate = value;}     }      // and here we turn serialization of the value on/off per the value     [Browsable(false), EditorBrowsable(EditorBrowsableState.Never)]     public bool ShouldSerializeAccountExpirationDateSerialized()     {         return AccountExpirationDate.HasValue;     }      // test it...     static void Main()     {         var ser = new XmlSerializer(typeof(Account));         var obj1 = new Account { AccountExpirationDate = DateTime.Today };         ser.Serialize(Console.Out, obj1);         Console.WriteLine();         var obj2 = new Account { AccountExpirationDate = null};         ser.Serialize(Console.Out, obj2);     } } 

This will only include the attribute when there is a non-null value.