Survey Results

namespace Questionable
{
    using System;

    /// <summary>
    /// Providesfor providing error reporting for function calls, without using exceptions.
    /// </summary>
    /// <typeparam name="TResult">The type of the result.</typeparam>
    /// <typeparam name="TError">The type of the error. This is typically an enumeration or a class with more error data.</typeparam>
    public class QuestionableReturn<TResult, TError>
    {
        private TResult result;

        /// <summary>
        /// Initializes a new instance of the <see cref="QuestionableReturn&lt;TResult, TError&gt;"/> class.
        /// </summary>
        /// <param name="result">The result.</param>
        public QuestionableReturn(TResult result)
        {
            this.HasResult = true;

            this.Result = result;
            this.Error = default(TError);
        }

        /// <summary>
        /// Initializes a new instance of the <see cref="QuestionableReturn&lt;TResult, TError&gt;"/> class.
        /// </summary>
        /// <param name="error">The error.</param>
        public QuestionableReturn(TError error)
        {
            this.HasResult = false;

            this.Result = default(TResult);
            this.Error = error;
        }

        /// <summary>
        /// Gets a value indicating whether this instance has a result, as opposed to an error.
        /// </summary>
        /// <value>
        ///     <see langword="true"/> if this instance has a result, as opposed to an error; otherwise, <see langword="false"/>.
        /// </value>
        public bool HasResult
        {
            get;
            private set;
        }

        /// <summary>
        /// Gets the result.
        /// </summary>
        /// <value>The result.</value>
        public TResult Result
        {
            get
            {
                if (this.HasResult)
                {
                    return this.result;
                }
                else
                {
                    throw new InvalidOperationException("A result is not available. Check the Error property for more information.");
                }
            }

            private set
            {
                this.result = value;
            }
        }

        /// <summary>
        /// Gets the error.
        /// </summary>
        /// <value>The error.</value>
        public TError Error
        {
            get;
            private set;
        }
    }

    /// <summary>
    /// A sample error enumeration.
    /// </summary>
    public enum SampleReturnError
    {
        /// <summary>
        /// The operation completed successfully.
        /// </summary>
        None = 0,

        /// <summary>
        /// The item was not found within the data.
        /// </summary>
        ItemNotFound,

        /// <summary>
        /// An internal error occurred.
        /// </summary>
        SomeOtherError
    }

    /// <summary>
    /// A sample class with a method demonstrating the questionable return model.
    /// </summary>
    public class SampleReturnClass
    {
        private static readonly string[] Data = { "FirstItem", "SecondItem", "BadItem" };

        /// <summary>
        /// Finds the string.
        /// </summary>
        /// <param name="index">The index of the string to find.</param>
        /// <returns>A questionable return value containing either a string result or an error.</returns>
        public QuestionableReturn<string, SampleReturnError> FindString(int index)
        {
            QuestionableReturn<string, SampleReturnError> returnValue;

            if (index >= Data.Length)
            {
                returnValue = new QuestionableReturn<string, SampleReturnError>(SampleReturnError.ItemNotFound);
            }
            else
            {
                string dataItem = Data[index];

                if (dataItem.Contains("Bad"))
                {
                    returnValue = new QuestionableReturn<string, SampleReturnError>(SampleReturnError.SomeOtherError);
                }
                else
                {
                    returnValue = new QuestionableReturn<string, SampleReturnError>(dataItem);
                }
            }

            return returnValue;
        }
    }
}

#define NULL 0

#define NULL (void*)

NullPointerException