Desculpe a resposta tardia - mas vi isso enquanto procurava outra coisa.
Basta fazer o seguinte:
SqlGeography theGeography;
int srid = 4326; // or alternative
DbGeography newGeography = DbGeography.FromText(theGeography.ToString(), srid);
Para reverter:
DbGeography theGeography;
SqlGeography newGeography = SqlGeography.Parse(theGeography.AsText()).MakeValid();
Espero que ajude!
