title: Default values for EF Core with enum to string Value Conversion
body: <p>EF Core 2.1+ supports <a href="https://docs.microsoft.com/en-us/ef/core/modeling/value-conversions" rel="nofollow noreferrer">Value Conversions</a>. You can use the built-in <code>EnumToStringConverter&lt;&gt;</code> to automatically convert an Enum to string, and vice versa.</p>
  
  <p>I'm connecting to an existing database and would like one of the columns to be converted to an Enum, so <code>EnumToStringConverter&lt;&gt;</code> seems to be right up my alley. However, the database is also outside of my control (I only have read access) so what happens if anyone inserts a row into the table with a string value that does not match any of my enum definitions?</p>
  
  <p>Preferrably I would like any unknown values to be mapped to an <code>Unknown</code> enum value, but I can't find any documentation on how to do this other than to manually create my own <code>ValueConverter</code> object where I implement my own manual parsing of all string values and map them to the appropriate enum value. This seems a bit cumbersome and adds additional maintenance, so I would very much like to have some automation here... meaning that if an unknown string value is found in the database, EFCore automatically maps this to my custom <code>Unknown</code> enum value.</p>
  
  <p>Is this possible?</p>