Table of Contents

Struct Result<TValue>

Namespace
FunctionalDdd
Assembly
FunctionalDdd.RailwayOrientedProgramming.dll

Represents either a successful computation (with a value) or a failure (with an Error).

public readonly struct Result<TValue> : IResult<TValue>, IResult, IEquatable<Result<TValue>>

Type Parameters

TValue

Success value type.

Implements
IResult<TValue>
Inherited Members
Extension Methods

Examples

// Creating results
Result<User> success = Result.Success(user);
Result<User> failure = Error.NotFound("User not found");

// Pattern matching
var message = result switch
{
    { IsSuccess: true } => $"Found user: {result.Value.Name}",
    { IsFailure: true } => $"Error: {result.Error.Detail}"
};

// Chaining operations
var finalResult = GetUser(id)
    .Bind(user => ValidateUser(user))
    .Map(user => user.Name);

Remarks

Result is the core type for Railway Oriented Programming. It forces explicit handling of both success and failure cases, making error handling visible in the type system. Use Result when an operation can fail in a predictable way that should be handled by the caller.

Properties

Error

Gets the error if the result is a failure; otherwise throws.

public Error Error { get; }

Property Value

Error

The error describing why the result failed.

Remarks

Always check IsFailure before accessing this property, or use TryGetError(out Error) instead.

Exceptions

InvalidOperationException

Thrown when accessing Error on a successful result.

IsFailure

True when the result represents failure.

public bool IsFailure { get; }

Property Value

bool

True if failed; otherwise false.

IsSuccess

True when the result represents success.

public bool IsSuccess { get; }

Property Value

bool

True if successful; otherwise false.

Value

Gets the underlying value if the result is successful; otherwise throws.

public TValue Value { get; }

Property Value

TValue

The success value.

Remarks

Always check IsSuccess before accessing this property, or use TryGetValue(out TValue) instead.

Exceptions

InvalidOperationException

Thrown when accessing Value on a failed result.

Methods

Deconstruct(out bool, out TValue?, out Error?)

Deconstructs the result into its components for pattern matching.

public void Deconstruct(out bool isSuccess, out TValue? value, out Error? error)

Parameters

isSuccess bool

True if the result is successful; otherwise false.

value TValue

The success value if successful; otherwise default.

error Error

The error if failed; otherwise null.

Examples

var (success, value, error) = GetUser(id);
if (success)
    Console.WriteLine($"User: {value.Name}");
else
    Console.WriteLine($"Error: {error.Detail}");

Equals(Result<TValue>)

Determines whether the specified result is equal to the current result.

public bool Equals(Result<TValue> other)

Parameters

other Result<TValue>

The result to compare with the current result.

Returns

bool

True if the specified result is equal to the current result; otherwise false.

Remarks

Two results are equal if they have the same success/failure state and equal values/errors.

Equals(object?)

Determines whether the specified object is equal to the current result.

public override bool Equals(object? obj)

Parameters

obj object

The object to compare with the current result.

Returns

bool

True if the specified object is a Result and is equal to the current result; otherwise false.

GetHashCode()

Returns a hash code for the current result.

public override int GetHashCode()

Returns

int

A hash code for the current result.

ToString()

Returns a string representation of the result.

public override string ToString()

Returns

string

A string in the format "Success(value)" or "Failure(ErrorCode: detail)".

TryGetError(out Error)

Attempts to get the error without throwing.

public bool TryGetError(out Error error)

Parameters

error Error

When this method returns true, contains the error; otherwise, null.

Returns

bool

True if the result is a failure; otherwise false.

Remarks

This is the recommended safe way to access the error without exception handling.

TryGetValue(out TValue)

Attempts to get the success value without throwing.

public bool TryGetValue(out TValue value)

Parameters

value TValue

When this method returns true, contains the success value; otherwise, the default value.

Returns

bool

True if the result is successful; otherwise false.

Remarks

This is the recommended safe way to access the value without exception handling. Similar to the TryParse pattern in .NET.

Operators

operator ==(Result<TValue>, Result<TValue>)

Determines whether two results are equal.

public static bool operator ==(Result<TValue> left, Result<TValue> right)

Parameters

left Result<TValue>

The first result to compare.

right Result<TValue>

The second result to compare.

Returns

bool

True if the results are equal; otherwise false.

implicit operator Result<TValue>(Error)

Implicitly converts an error to a failed result.

public static implicit operator Result<TValue>(Error error)

Parameters

error Error

The error to wrap in a failed result.

Returns

Result<TValue>

A failed result containing the error.

implicit operator Result<TValue>(TValue)

Implicitly converts a value to a successful result.

public static implicit operator Result<TValue>(TValue value)

Parameters

value TValue

The value to wrap in a success result.

Returns

Result<TValue>

A successful result containing the value.

operator !=(Result<TValue>, Result<TValue>)

Determines whether two results are not equal.

public static bool operator !=(Result<TValue> left, Result<TValue> right)

Parameters

left Result<TValue>

The first result to compare.

right Result<TValue>

The second result to compare.

Returns

bool

True if the results are not equal; otherwise false.

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