Flatten nested collections with SelectMany.
C#: Concatenate the items from several sequences into one sequence.
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;
var rows = new[] {new[] {1, 2}, new[] {3}};
Console.WriteLine(string.Join(",", rows.SelectMany(row => row)));Expected output EXAMPLE
1,2,3
Details
Use Program.cs in a .NET 8 console project and run dotnet run. Uses only the .NET standard libraries. Concatenate the items from several sequences into one sequence.
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
2e8df81ec91152f055374420605448fa33e7595d25865125e86ba8e7385bdfe0- 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
1,2,3
Exit code: 0. Standard error: empty. Validation: Exact stdout comparison. System-dependent values above are one recorded run.