union type in action.cs

Union<TSuccess, TError> DoSomeWork( ... ) {
    if (/* Happy path */) {
        TSuccess happyResult;
        return happyResult;
    }

    // else
    return new TError();
}

var result = DoSomeWork( ... );
result.Match(
    happyResult => { /* Do some more with happy path result */ },
    err => { /* explicit error handling */ }
);