Incendium.Result 1.0.4

Incendium.Result

Incendium.Result is a small .NET Standard 2.1 library, which provides Error, Result<T> and NullableResult<T> useful types.

These types allow you to return success value or error from asynchronous and synchronous methods without explicit indication of the result type when returning and with convenient type deconstruction during processing the result.

These type also can be used for less error handling through exception mechanisms where possible.

Getting started

Installation

PM> Install-Package Incendium.Result

Result<T>

If you need to return either a not-null value or an error from a method, you can use the Result<T> type:

public async Result<string> GetStringAsync() {
    // ...
    if (condition1) {
        return "Test string result";
    } else {
        return new Error(code: 123, message: "Test error");
    }

    try {
        // ...
    } catch (Exception e) {
        return new Error(code: 321, message: "Test error", exception: e);
    }
}

Then processing the result might look like this:

var (str, error) = await GetStringAsync();

if (error != null) {
    log.LogError(
        error.Exception(),
        "Error with code {@code} and message {@message}",
        error.Code,
        error.Message);
}

The Result<T> instance can be created only from non-null value or from non-null error:

public Result<Foo> GetFooAsync() {
    return new Foo(); // correct
    // return new Error(); // correct
    // return (Foo)null; // incorrect, CS8600 and CS8625 warnings, throws ArgumentNullException
    // return (Foo)null!; // incorrect, throws ArgumentNullException
    // return (Foo?)null; // incorrect, CS8625 warning, throws ArgumentNullException
    // return (Foo?)null!; // incorrect, throws ArgumentNullException
    // return (Error)null; // incorrect, CS8600 and CS8625 warnings, throws ArgumentNullException
    // return (Error)null!; // incorrect, throws ArgumentNullException
    // return (Error?)null; // incorrect, CS8625 warning, throws ArgumentNullException
    // return (Error?)null!; // incorrect, throws ArgumentNullException
}

NullableResult<T>

If the successful return value can be null, you must use the NullableResult<T> type:

public NullableResult<Foo> GetFooAsync() {
    return new Foo(); // correct
    // return new Error(); // correct
    // return (Foo?)null; // correct
    // return (Foo)null; // correct with CS8600 warning
    // return (Foo)null!; // correct
    // return (Error)null; // incorrect, CS8600 and CS8625 warnings, throws ArgumentNullException
    // return (Error)null!; // incorrect, throws ArgumentNullException
    // return (Error?)null; // incorrect, CS8625 warning, throws ArgumentNullException
    // return (Error?)null!; // incorrect, throws ArgumentNullException
}