Map & Bind

Map — Transform the Value

Map applies a function to the inner value if it is a success. Errors pass through unchanged — you stay on the “happy rail”.

// Sync
ApiResult<string> title = ApiResult.Ok(todo)
    .Map(t => t.Title.ToUpperInvariant());

// Async
ApiResult<string> title = await ApiResult.Ok(todo)
    .MapAsync(async t => await EnrichTitleAsync(t.Title));

Use Map when transforming data without introducing new failure cases.

Bind — Chain Operations

Bind (flatMap) sequences operations where each step can itself fail. It unwraps the value and passes it to a function that returns a new ApiResult<TResult>, preventing nested ApiResult<ApiResult<T>>.

// Sync
ApiResult<string> result = ApiResult.Ok(42)
    .Bind(id => id > 0
        ? ApiResult.Ok(id.ToString())
        : ApiResult.HttpFail<string>(HttpStatusCode.BadRequest, "Invalid id"));

// Async
ApiResult<string> result = await ApiResult.Ok(42)
    .BindAsync(async id => await FetchUserAsync(id));

Use Bind when the next operation can also fail.

Map vs Bind — at a glance

	Input	Output
`Map`	`T`	`TResult` (transform only)
`Bind`	`T`	`ApiResult<TResult>` (can fail)