C# Cheat Sheet

C# cheat sheet with real commands and snippets for setup, core workflows, debugging, and production-safe automation patterns. If you are working across tools, pair this with the SQL Cheat Sheet and Docker Cheat Sheet.

Setup and Tooling

Goal: Install and verify language toolchain

# Run dotnet command
dotnet --version

# Run dotnet command
dotnet new console -n App

# Run cd command
cd App

Core Workflows

Goal: Run and build source code

# Execute dotnet workflow
dotnet run

# Execute dotnet workflow
dotnet build

Goal: Use a practical code snippet

using System;

public class Program
{
    public static void Main()
    {
        Console.WriteLine("Hello C#");
    }
}

Testing and Formatting

Goal: Run automated tests

# Execute test-related command
dotnet test

# Execute test-related command
dotnet test --collect:"XPlat Code Coverage"

Goal: Run lint and formatter checks

# Execute quality command
dotnet format

# Execute quality command
dotnet build -warnaserror

Automation and CI

Goal: Create a repeatable CI shell step

# Run strict shell mode for CI step
set -euo pipefail

# Install dependencies deterministically
npm ci || pip install -r requirements.txt || true

# Run tests and fail fast on errors
dotnet test

Debugging and Troubleshooting

Goal: Trace runtime issues

# Print runtime and package manager versions
node --version || python --version || true

# Search stack traces and TODO markers
rg "Traceback|Exception|TODO" .

# Re-run tests with verbose output
dotnet test -v || dotnet test --verbose || true

Common Gotchas

• Pin C# language/runtime versions in local and CI environments.
• Keep formatting and linting automated to avoid noisy diffs in code review.
• Prefer explicit dependency lock files for reproducible builds.
• Write small, deterministic tests that can run quickly in pre-commit checks.
• Document compiler/interpreter flags used in production builds.

Related Sheets

• SQL Cheat Sheet — query patterns, joins, and data analysis.
• Docker Cheat Sheet — container build, run, and image lifecycle workflows.
• CSS Cheat Sheet — daily CSS commands and production-ready examples.