Let’s assume we have this simple C# class which represents some XML data (i.e. it’s serialized to XML eventually)

[XmlType(AnonymousType = true)]
public partial class Employee
{
   [XmlAttribute(AttributeName = "id")]
   public string Id { get; set; }

   [XmlAttribute(AttributeName = "name")]
   public string Name { get; set; }

   [XmlAttribute(AttributeName = "age")]
   public int Age { get; set; }
}

Under certain circumstances we may prefer to not include elements in the XML if the values are not suitable.

We could handle this is a simplistic manner by setting a DefaultValueAttribute on a property and obviously the data will not be serialized unless the value differs from the default, but this is not so useful if you wanted more complex functionality to decide whether a value should be serialized or not, for example what if we don’t want to serialize Age if it’s less than 1 or greater than 100. Or not serialize Name if it’s empty, null or the string length is less than 3 characters and so on.

ShouldSerializeXXX

Note: You should not use ShouldSerializeXXX method and the DefaultValueAttribute on the same property

So, we can now achieve this more complex logic using the ShouldSerializeXXX method. If we create a partial class (shown below) and add the ShouldSerializName method we can tell the serializer to not bother serializing the Name property under these more complex circumstances

public partial class Employee
{
   public bool ShouldSerializeName()
   {
      return !String.IsNullOrEmpty(Name) || Name.Length < 3;
   }
}

When serializing this data the methods are called by the serializer to determine whether a property should be serialized and obviously if it should not be, then the element/attribute will not get added to the XML.