## MEF catalogs implement IEnumerable and therefore can no longer be used to create a serializer

### Scope
Major

### Version Introduced
4.5

### Source Analyzer Status
Available

### Change Description

Starting with the .NET Framework 4.5, MEF catalogs implement IEnumerable and
therefore can no longer be used to create a serializer
(<xref:System.Xml.Serialization.XmlSerializer?displayProperty=name> object).
Trying to serialize a MEF catalog throws an exception.

- [ ] Quirked
- [ ] Build-time break

### Recommended Action

Can no longer use MEF to create a serializer

### Affected APIs
* Not detectable via API analysis

### Category
Managed Extensibility Framework (MEF)

<!-- breaking change id: 12 -->