Result¶

Represents the result that is either a success or a failure.

It is a struct, preventing you from returning null instead.

This come in two forms:

without a payload - Result
with a payload - Result<T>

There are async version of all the extension methods.

There are extension methods that allow you to easily convert dotnet or third-party dotnet libraries to return Result.

Any method that can fail should return a Result or Result<T>

ResultError¶

Failures are represented as an IResultError.

These represent the context of the error.

Built-in¶

There are a number of built-in IResultError implementations.

You are free to create your own, by implementing either the IResultErrorNonComposite or IResultErrorComposite interfaces.

ResultErrorMessage¶

Represents a string error message, without any other context.

ResultErrorException¶

Represents a exception error.

ResultErrorEmpty¶

Represents an empty error message, this is mainly used internally in the library.

ResultErrorComposite¶

This is a special IResultError, it allows you to have a tree structure of IResultError's.

What to do with them¶

There are two supported ways to get the data from an IResultError:

GetErrorString
GetErrorStructure

GetErrorString¶

This gets a string representing the error(s). Different implementation of IResultError deal with this differently.

ResultErrorComposite will create a string of its children separating them with the specified separator.

GetErrorStructure¶

This gets a tree structure representing the error(s).

This tree structure is serializable to Json.

Extension Methods¶

Combine¶

Allows you to combine multiple Result's into one, if they have the same payload types.

If there is no payload on the Results passed in:¶

If all of the Results passed are success, then return a Result success
If any of the Results passed are failed, then return a Result failure with a ResultError of all of the failure ResultError's

If there are payloads on the Results passed in and they are all the same type:¶

If all of the Results passed are success, then return a Result success with an IEnumerable of all the Result payloads
If any of the Results passed are failed, then return a Result failure with a ResultError of all of the failure ResultError's

If there are IEnumerable payloads on the Results passed in and they are all the same type:¶

If all of the Results passed are success, then return a Result success with an IEnumerable of all the Result payloads concatenated together
If any of the Results passed are failed, then return a Result failure with a ResultError of all of the failure ResultError's

CombineAll¶

Allows you to combine Result's that have different payload types.

You additionally pass in a selector func.

Compensate¶

Allows you to provide a compensating action (that also returns a Result), if there Result is a failure.

CompensateWhen¶

Allows you to provide a compensating action (that also returns a Result), if there Result is a failure of a specific type and optionally matches a predicate.

CompensateWhenAny¶

Allows you to provide a compensating action (that also returns a Result), if there Result is a failure of a specific type and optionally matches a predicate.

Note: this will flatten and search a ResultErrorComposite.

Do - Perform side-effect only on success¶

Executes a side-effect if the Result is success.

DoSwitch - Perform side-effect¶

The DoSwitch extension methods allow you to perform a side-effect on an Result<T>.

You have to say what to do when the value is success and failure.

DoWhenFailure - Perform side-effect only on failure¶

Executes a side-effect if the Result is failure.

EnhanceWithError¶

Allows you to provide additional context to a failure.

Factory¶

Result.Ok and Result.Ok<T>¶

Creates a success Result

or

Creates a success Result<T> with the payload provided

Result.Fail¶

Creates a failure Result with the error provided

or

Creates a failure Result<T> with the error provided

ToResultOk - Result -> Result<T>¶

Creates a success Result<T> with the payload provided

FlatMap¶

Map - Result<T> -> Result<TR>¶

The Map extension methods allow you to transform an Result<T> to an Result<TR>.

The transformation will only occur if there is the Result is success.

It is assumed that the transformation func that you pass in cannot fail, i.e. throw an exception. If it can throw an exception, use then, returning a Result<TR> from the transformation func.

MapSwitch¶

Switch¶

The Switch extension methods allow you to transform an Result<T> to a TR.

You have to say what to return when the value is success and failure.

Then - Result<T> -> Result<TR>¶

The Then extension methods allow you to bind two Result or Result<T> methods together.

ThenSwitch¶

ThenTry¶

This can be a good way to integrate third-party libraries.

ToNonGeneric - Result.Ok<T> -> Result¶

The ToNonGeneric extension methods discards the payload.

Try¶

Will run the func wrapping it in a try / catch.

If an exception is thrown, it will return a Result.Fail
If no exception is thrown it will return a Result.Ok

This can be a good way to integrate third-party libraries.

Unwrap - Result.Ok<T> -> T or Exception¶

Comes out of the Result monad.

If the Result is Ok, then return the value if there is one
If the Result is Fail, then throw an exception, passing through the ResultError data

Enumerable¶

Choose¶

Filter¶

FlatMapAs¶

MapAs¶

Pick¶

PickFailureOrSuccess¶

ThenAs¶

TryToDictionary¶

AsyncEnumerable¶

Choose¶

Filter¶

MapAs¶

Interop with Option¶

Option -> Result¶

You can move between an Option and a Result using the 'ToResult' extension method. You just need to provide the error if the Option is not present.

Result -> Option¶

This is not supported as it would result in the loss of the error context.