Find a matching item with a fallback.
C#: Use the FirstOrDefault overload with an explicit default value.
using System;
using System.IO;
using System.Linq;
using System.Text;
using System.Text.Json;
using System.Text.RegularExpressions;
using System.Collections.Generic;
using System.Globalization;
using System.Security.Cryptography;
using System.Threading;
using System.Threading.Tasks;
Console.WriteLine(new[] {3, 8, 10}.FirstOrDefault(n => n % 2 == 0, -1));Expected output EXAMPLE
8
Details
Use Program.cs in a .NET 8 console project and run dotnet run. Uses only the .NET standard libraries. Use the FirstOrDefault overload with an explicit default value.
Tested on Ubuntu 24.04.5 LTS · · 8.0.425 · libc6 2.39-0ubuntu8.9
Test inputs, results and environment
The exact published code ran in a dedicated Linux test container with prepared inputs. Unprivileged snippet process, external networking disabled, read-only root filesystem, and a fresh temporary working directory. Fixtures and output records are isolated from the application database. Testing covers this example and its stated checks, not every input, operating system, or runtime version. The Linux container shares its host's kernel; this is not a native Windows test.
- Architecture / host kernel
- x86_64 / 6.18.54.1-microsoft-standard-WSL2
- Snippet identity / locale
- uid=65534, gid=65534 (unprivileged) / C.UTF-8
- Interpreter invocation
dotnet build --no-restore && dotnet out/csharp.dll- Container image ID
sha256:32dc2d998158b6554c99b73b533f423696a0f3e31e8cbea9db10b5eee9a2fadd- Code SHA-256
9940bd31fb5bdc7642c6f00b1d5716d3c9033a6a9afa80f9f1469c030b9f1f77- Dependencies
- libc6 2.39-0ubuntu8.9
Test input setup
These are the prepared inputs used by the test harness. See Details above for the prerequisites and how to run this example.
# No input files required.
Observed standard output
8
Exit code: 0. Standard error: empty. Validation: Exact stdout comparison. System-dependent values above are one recorded run.