DotNetElements.Core.Result 0.1.9

About

This project provides simple Result and Result<TValue> types to be used as return types of functions as an alternative to exceptions.

The default types have a .IsOk and .IsFail property to check wether the function returned success or failure. In case of a Result<TValue> the result contains the return value of the function.

To include error state in the Result, one has to implement a custom ErrorResult<TValue, TError>. A source generator automatically provides the class implementation.

There are helper functions like Fail(), Ok() or TryGetValue(out string? resultValue) to make working with Results as simple as possible.

Recommended setup

1. Install nuget package > dotnet add package DotNetElements.Core.Result --version <insert-latest-version-here>

2. Add the following to a GlobalUsing.cs

global using static DotNetElements.Core.ResultObject.ResultHelper;

Usage examples for basic Result and Result<TValue> types

Example function using a Result as return type

static Result<string> GetResultFunction(bool expectedResult)
{
    // With logging
    if (!expectedResult)
        return Fail(() => Console.WriteLine("Fail from method"));

    // Without logging
    if (!expectedResult)
        return Fail();

    return "Success from method";
}

Usage example using the .TryGetValue semantic

if (GetResultFunction(true).TryGetValue(out string? resultValue))
{
    Console.WriteLine($"Success from caller with value <{resultValue}>");
}
else
{
    Console.WriteLine("Fail from caller";
}

Usage example using manual check and GetValueUnsafe()

Result<string> result = GetResultFunction(false);

if (result.IsOk)
{
    Console.WriteLine($"Success from caller with value <{result.GetValueUnsafe()}>");
}
else
{
    Console.WriteLine("Fail from caller");
}

Usage example using explicit conversions to prevent data loss for Result with value

Result resultWithoutValue = result.AsResult();

Usage examples for source generated custom ErrorResult<TError> and ErrorResult<TValue, TError> types

Define a custom ErrorResult

namespace MyNamespace;

public enum CrudError
{
  InternalError,
  NotFound,
  DuplicateEntry
}

[ErrorResult<CrudError>]
public partial class CrudResult<TValue>;

Example function using a custom CrudResult as return type

// This is needed to enable the usage of Ok() and Fail methods
// Can be in each file or in a GlobalUsing.cs
using static MyNamespace.CrudResultHelper;

static CrudResult<string> GetCrudResultFunction(bool expectedResult)
{
    // With logging
    if (!expectedResult)
        return Fail(CrudError.InternalError, () => Console.WriteLine("Fail from method"));

    // Without logging
    if (!expectedResult)
        return Fail(CrudError.InternalError);

    return "Success from method";
}

Usage example using the .TryGetValue semantic

if (GetCrudResultFunction(true).TryGetValue(out string? crudValue, out CrudError? error))
{
    Console.WriteLine($"Success from caller with value <{crudValue}>");
}
else
{
    Console.WriteLine($"Fail from caller with error <{error}>");
}

Usage example using manual check and GetValueUnsafe()

CrudResult<string> crudResult = GetCrudResultFunction(false);

if (crudResult.IsOk)
{
    Console.WriteLine($"Success from caller with value <{crudResult.GetValueUnsafe()}>");
}
else
{
    Console.WriteLine($"Fail from caller with error <{crudResult.GetErrorUnsafe()}>");
}

Usage example using explicit conversions to prevent data loss

CrudResult crudResultWithoutValue = crudResult.AsCrudResult();
Result<string> simpleResultWithValue = crudResult.AsResultWithValue();
Result simpleResultWithoutValue = crudResult.AsResult();