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Async Programming with Monads

Both Result<T> and Maybe<T> provide full async support for all major operations.

Async Result Operations​

Async Map​

var result = await Result.Success("file.txt")
    .Map(async fileName => await File.ReadAllTextAsync(fileName));

Async Bind​

public async Task<Result<User>> GetUserAsync(int id) =>
    await ValidateId(id)
        .Bind(async validId => await database.GetUserAsync(validId));

Async Side Effects​

var result = await CreateUserAsync(email)
    .IfSuccess(async user => await SendWelcomeEmailAsync(user))
    .IfFailure(async error => await LogErrorAsync(error));

Async Match​

var message = await result.Match(
    async user => await FormatUserDetailsAsync(user),
    async error => await FormatErrorMessageAsync(error)
);

Async Ensure​

var validated = await result
    .Ensure(async user => await IsUserActiveAsync(user),
            new LogicError("User is not active"));

Async Maybe Operations​

Async Map​

var maybe = await Maybe.Some("data")
    .Map(async data => await ProcessDataAsync(data));

Async Bind​

var result = await Maybe.Some(userId)
    .Bind(async id => await FindUserAsync(id));

Async Side Effects​

await maybe
    .IfSome(async value => await ProcessValueAsync(value))
    .IfNone(async () => await HandleMissingValueAsync());

Task Extensions​

All methods work seamlessly with Task<Result<T>> and Task<Maybe<T>>:

public async Task<Result<ProcessedData>> ProcessUserDataAsync(int userId)
{
    return await GetUserAsync(userId)          // Task<Result<User>>
        .Bind(async user => await GetUserDataAsync(user.Id))
        .Map(async data => await ProcessDataAsync(data))
        .IfSuccess(async result => await CacheResultAsync(result));
}

Safe Async Execution​

// Catches exceptions as RuntimeError
var result = await Result.Execute(async () =>
    await RiskyAsyncOperation()
);

See Also​