Preserve an unknown enum number

Advanced · C#. An unknown member is still a valid stored integer. Keep its width and signedness instead of forcing it into a named application enum.

Run this example

Prerequisites: the repository's .NET 10 SDK and a checkout of this source. Run from the repository root:

dotnet run --project docs/examples/CStructSharp.Docs.Examples.csproj -c Release -- preserve-enum

The runner checks 4294967295 with no known name, unsigned 32-bit backing. Success includes PASS preserve-enum.

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Complete program

The layout, options, input bytes, helper methods, and required types are all included. To adapt it outside the repository, create a .NET 10 console project, add CStructSharp, and replace Program.cs with this complete file. These examples follow the source version; use a matching package when testing a release.

Download the complete C# source.

// Generated from executable documentation examples. Edit the source region, then regenerate.
using System;
using System.IO;
using System.IO.Pipelines;
using System.Linq;
using System.Buffers;
using System.Collections.Generic;
using System.Dynamic;
using System.Globalization;
using System.Numerics;
using System.Runtime.CompilerServices;
using System.Threading;
using System.Threading.Tasks;
using CStructSharp;
using CStructSharp.Codecs;
using CStructSharp.Diagnostics;
using CStructSharp.Introspection;
using CStructSharp.Values;

internal static partial class Program
{
    public static void Main()
    {
        PreserveEnum();
        Console.WriteLine("PASS preserve-enum");
    }

    private static void PreserveEnum()
    {
        var layout = new CStruct("enum state : uint32 { Known = 1 }; struct root { state value; };");
        var value = (EnumValueResult)layout.ReadValue(new byte[] { 0xFF, 0xFF, 0xFF, 0xFF }, "root.value")!;
        Equal(new BigInteger(uint.MaxValue), value.Value);
        Equal(null, value.Name);
        Equal(32, value.BitWidth);
        True(!value.IsSigned, "uint32 enum should be unsigned.");
    }

    private static void Equal<T>(T expected, T actual)
    {
        if (!EqualityComparer<T>.Default.Equals(expected, actual))
        {
            throw new InvalidOperationException($"Expected '{expected}', received '{actual}'.");
        }
    }

    private static void True(bool condition, string message)
    {
        if (!condition)
        {
            throw new InvalidOperationException(message);
        }
    }
}

Try it and diagnose mistakes

Change the input to 01 00 00 00.

Answer: The enum name is Known and its value is 1. The program contains assertions for its original inputs. When changing an input intentionally, update the expected assertion too; an unchanged assertion is not evidence that the new value is wrong.

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Table of Contents

Preserve an unknown enum number

Run this example

Complete program

Try it and diagnose mistakes