Result.cs

Result.cs

    public class Result
    {
        public ICollection<string> Messages { get; set; } = new List<string>();
        public ResultStatus Status = ResultStatus.Ok;

        public static Result<bool> Validate(bool condition, string error)
            => condition
                   ? new Result<bool>()
                   : new Result<bool> {Status = ResultStatus.Invalid, Messages = new List<string> {error}};
    }

    public class Result<T> : Result
    {
        public T Data { get; set; }
    }

    public enum ResultStatus
    {
        Ok,
        Invalid,
        Failed,
    }

    public static class ResultExtensions
    {
        public static Result<T> Validate<T>(this Result<T> prevResult,
                                            bool condition,
                                            string error) =>
            prevResult.Status switch
            {
                ResultStatus.Failed => prevResult,
                _ => condition
                         ? prevResult
                         : new Result<T>
                         {
                             Messages = prevResult.Messages.Concat(new[] {error}).ToList(),
                             Status = ResultStatus.Invalid
                         }
            };

        public static Result<T> Validate<T>(this Result<T> prevResult,
                                            Func<T, bool> condition,
                                            string error) =>
            prevResult.Status switch
            {
                ResultStatus.Failed => prevResult,
                _ => condition(prevResult.Data)
                         ? prevResult
                         : new Result<T>
                         {
                             Status = ResultStatus.Invalid,
                             Messages = prevResult.Messages.Concat(new[] {error}).ToList()
                         }
            };

        public static Result<F> Map<T, F>(this Result<T> prevResult, Func<T, F> function) =>
            prevResult.Status switch
            {
                ResultStatus.Ok => new Result<F> {Data = function(prevResult.Data)},
                _ => new Result<F> {Status = ResultStatus.Failed, Messages = prevResult.Messages}
            };
    }