This ReflectionLoadTypeException is most often caused because the DLLs you're using aren't up to date so the dependency chain fails. Use nuget to update your project with the latest DLLs. v0.16.2.2 of the PostgreSql provider requires
- Simple.Data.Core (≥ 0.12.2.2)
- Simple.Data.Ado (≥ 0.12.2.2)
- Npgsql (≥ 2.0.11)
(via Mark Rendle) Try explicitly installing 0.16.2.2 of Simple.Data.Ado first, then installing the Postgres package.