Result<T, E> API

Every method on Result<TOk, TErr>, grouped by what it does.

Result<TOk, TErr> holds either a success value (Ok<TOk, TErr>) or a failure (Err<TOk, TErr>). Neither side can hold null.

This is the lookup. If you are learning the type rather than looking a method up, read the Result<T, E> guide first.

The five categories match the Option<T> reference exactly, so a reader who knows one tree can navigate the other.

Creation

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Method	What it does
Result.Ok<TOk, TErr>(value)	The success case. Throws on null.
Result.Err<TOk, TErr>(error)	The failure case. Throws on null.
Result.Ok<TOk>(value)	The same, defaulting TErr to Error.
Result.Err<TOk>(error)	The same, defaulting TErr to Error.
Result.Try(factory, onError)	Runs a factory that might throw.
Result.Try<TOk>(factory)	The same, converting the exception with Error.FromException.
Result.TryAsync(…)	The same, for a factory returning a Task.

Transform

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Method	What it does
Map	Changes the success value.
MapErr	Changes the error.
AndThen	Chains a step that itself returns a Result, without nesting.
And	The second result, if the first was Ok.
Or	The first Ok of the two.
OrElse	The same, building the second only if needed.

Consume

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Member	What it does
IsOk / IsErr	The state, as a bool.
IsOkAnd / IsErrAnd	The state combined with a predicate.
Match	Both branches, one plain value out.
Deconstruct	Lets C# pattern matching bind either side positionally.
Unwrap	The success value, or an UnwrapException.
UnwrapErr	The error, or an UnwrapException.
UnwrapOr	The success value, or the fallback you supplied.
UnwrapOrElse	The success value, or one built from the error.
UnwrapOrDefault	The success value, or default(TOk).
UnwrapOrNull	The success value, or null. Value types only.
Expect	Like Unwrap, with your own exception message.
ExpectErr	Like UnwrapErr, with your own exception message.
MapOr	Transforms the success value, or returns your fallback.
MapOrElse	The same, building the fallback from the error.
MapOrDefault	The same, falling back to default(TOut).
MapOrNull	The same, falling back to null. Value types only.

Side effects

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Method	What it does
Inspect	Runs an action on the success value and hands the result back.
InspectErr	The same, on the error.

Nesting and conversion

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Method	What it does
Flatten	Collapses a Result<Result<TOk, TErr>, TErr>.
Transpose	Turns a Result<Option<T>, E> into an Option<Result<T, E>>.
GetOk	Converts to an Option, keeping the success value.
GetErr	Converts to an Option, keeping the error.

Collections

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Method	What it does
Flatten	Keeps the successes, drops the failures.
FlattenErr	Keeps the failures, drops the successes.
Partition	Both halves, reading the source once.
Collect	Ok of every value, or Err carrying the first failure.
CollectAsync	The same, over an IAsyncEnumerable.
AsEnumerable	Treats one result as a sequence of nothing or one.

Async

Every method above has an Async counterpart. They are extension methods on the task that wraps the result, not on the result itself — see Async.

State overloads

Most methods that take a delegate also take one that receives your data instead of capturing it. See State overloads.