Immutable — Once a Result is created, it cannot be changed.
Detailed on Failure — A Result, when failed, contains a specific Error class.
Thread safe — Results are immutable and by nature, safe to work with in multithreaded scenarios.
Extensible — Extend the Error class by introducing your very own Error classes.
Fully tested — The code has full coverage.
Usage
Result objects can hold values or simply be used as flow state control. The values can be anything. A class, a
value-type, a struct, anything.
Creating a Result
Typically, the Result class is being used by methods that don't return a value.
var result = Result.Success();
var result = Result.Fail();
// the error can also hold a message
var error = new Error("An error occured.");
var result = Result.Fail(error);
// the error can also hold an exception
var error = new Error("An error occured.", new Exception());
var result = Result.Fail(error);
An example usage of the Result class.
public async Task<Result> ExecuteJob()
{
try
{
var jobId = ExecuteCleanupJob();
if (jobId == 0)
{
// create an Error indicating the reason of failure
var error = new Error("Cleanup job was not executed.");
return Result.Fail(error);
}
return Result.Success();
}
catch (Exception ex)
{
// create an Error and attach the exception
var error = new Error("An unexpected error occured while trying execute Cleanup job.", ex);
return Result.Fail(error);
}
}
The Result<T> class is being used by methods that return a value.
var result = Result<int>.Success(1);
var result = Result<int>.Fail();
// the error can also hold a message
var error = new Error("An error occured.");
var result = Result.Fail(error);
// the error can also hold an exception
var error = new Error("An error occured.", new Exception());
var result = Result<int>.Fail(error);
An example usage of the Result<T> class.
public async Task<Result<int>> ExecuteJob()
{
try
{
var jobId = ExecuteCleanupJob();
if (jobId == 0)
{
// create an Error indicating the reason of failure
var error = new Error("Cleanup job was not executed.");
return Result<int>.Fail(error);
}
return Result<int>.Success(jobId);
}
catch (Exception ex)
{
// create an Error and attach the exception
var error = new Error("An unexpected error occured while trying execute Cleanup job.", ex);
return Result<int>.Fail(error);
}
}
The anatomy of a Result
A Result holds certain information about itself.
var result = Result.Success();
result.IsSuccessful // true
result.IsFailed // false
result.Error // throws InvalidOperationException as the result is not in a failed state
var result = Result.Fail();
result.IsSuccessful // false
result.IsFailed // true
result.Error // Error instance
When the Result<T> holds a return value.
var result = Result<int>.Success(1);
result.IsSuccessful // true
result.IsFailed // false
result.Value // 1
result.Error // throws InvalidOperationException as the result is not in a fail state
var result = Result<int>.Fail();
result.IsSuccessful // false
result.IsFailed // true
result.Value // throws InvalidOperationException as the result is not in a success state
result.Error // IError instance
Extending
You can introduce your very own Error classes by extending the existing one.
The below custom NotFoundError class is being used when an application might need to return a NotFound 404 response.
public interface IHttpError : IError
{
public HttpStatusCode HttpStatusCode { get; }
}
public sealed class NotFoundError : Error, IHttpError
{
public HttpStatusCode HttpStatusCode => HttpStatusCode.NotFound;
public NotFoundError(string message)
: base(message)
{
}
}
An example of the above custom Error class.
public async Task<Result<IEnumerable<Project>>> GetProjects()
{
try
{
var projects = await GetProjects();
if (!projects.Any())
{
var error = new NotFoundError("The request resource was not found."); // <-- the new NotFoundError Error class
return Result<IEnumerable<Project>>.Fail(error);
}
return Result<IEnumerable<Project>>.Success(jobId);
}
catch (Exception ex)
{
// create an Error and attach the exception
var error = new Error("An unexpected error occured while trying execute Cleanup job.", ex);
return Result<IEnumerable<Project>>.Fail(error);
}
}
The Error class provides 2 constructors, so you are free to use whichever suits your needs
best. See definition
