Controlling order of serialization in C#

[XmlElementAttribute(Order = 1)] 
public int Field1 {...} 

[XmlElementAttribute(Order = 2)] 
public int Field2 {...} 

Catch: You must specify the Order for all of your members.

Be careful - deserialization will only work if the properties in the XML document are in the same order. Otherwise it will silently ignore out-of-order properties.

XmlElementAttribute.Order, which controls "the explicit order in which the elements are serialized or deserialized".