Repair an invalid path

Beginner · C#. Paths are case-sensitive. Fix the selected name instead of changing valid bytes.

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 -- invalid-path

The runner checks Header.kind fails; header.kind reads 2. Success includes PASS invalid-path.

Try the related browser lesson.

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()
    {
        InvalidPath();
        Console.WriteLine("PASS invalid-path");
    }

    private static void InvalidPath()
    {
        var layout = new CStruct("struct header { uint16 kind; uint32 length; };");
        byte[] bytes = [2, 0, 6, 0, 0, 0];
#pragma warning disable CSG200 // The analyzer reports the wrong path at build time; this recipe shows the runtime failure.
        Throws<CStructPathException>(() => layout.ReadValue(bytes.AsSpan(), "Header.kind"));
#pragma warning restore CSG200
        Equal((ushort)2, (ushort)layout.ReadValue(bytes.AsSpan(), "header.kind")!);
    }

    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 Throws<TException>(Action action)
        where TException : Exception
    {
        try
        {
            action();
        }
        catch (TException)
        {
            return;
        }

        throw new InvalidOperationException($"Expected {typeof(TException).Name}.");
    }
}

Try it and diagnose mistakes

Misspell kind as kinds.

Answer: The selected read raises CStructPathException. Restore kind to fix it. 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.

Continue with the related guide or choose another recipe.