The CommandType in ADO.NET is quite important. If Dapper can see your command-type at compile-time, but knows that it isn’t something it understands, then it isn’t sure what you want to do. If you genuinely have a need to use an unknown command-type, maybe log an issue, explaining the context!

Bad:

conn.Execute("somesql", commandType: (CommandType)42);

Good:

conn.Execute("somesql", commandType: CommandType.StoredProcedure);