c# - XmlSerializer: How to Deserialize an enum value that no longer exists

Question

I am using the XMLSerializer to save this class to a file. The class has a string and an enum as shown below:

public class IOPoint
{
     string Name {get; set;}
     TypeEnum {get; set;}
}


public enum TypeEnum
{
    Temperature,
    Pressure,
    Humidity,
}

When serialized it looks like this.

<IOPoint>
  <Name>Relative Humidity</Name>
  <TypeEnum>Humidity</TypeEnum>
</IOPoint>

I've been serializing and deserializing this object with no problems for several versions. I no longer want to support Humidity, so I removed it from the enum. However, this causes an exception when deserializing from XML because the value in the TypeEnum field, Humidity, is not a valid value for the TypeEnum. This makes sense, but how to handle this?

What I'd like to do is just ignore this error. And leave the value as null. I've tried implementing the OnUnknownElement XmlDeserilizationEvent class. Unfortunately, this does not catch this error.

Any ideas on how to catch and ignore this error (I can clean up after the deserialization is complete).

Mitch

Answer 1

You can mark the member Obsolete

public enum TypeEnum
{
    Temperature,
    Pressure,
    [Obsolete]
    Humidity
}