Debugging C#

Last reviewed May 28, 2026 Content v20260528

Track mode: server_compiled
Means: Compiled runner
Reading: ~1 min
Level: advanced

This lesson

This lesson teaches Debugging C#: the syntax, patterns, and safety habits you need before advancing in C#.

Teams still ship Debugging C# in C# codebases—skipping it leaves gaps in debugging and code reviews.

You will apply Debugging C# in contexts like: .NET services, Unity games, and Windows-centric tooling.

Write C# with Console.WriteLine (top-level or Program), click Run on server—the dev runner uses dotnet build/run on a temp net8 project (requires .NET SDK; LEARNING_RUNNER_ENABLED=true).

When pointers, structs, and basic control flow from intermediate lessons are familiar.

Debugging compiled C# uses IDE breakpoints, watches, and call stacks—like gdb for C++ but integrated with Roslyn symbols. Build Debug configurations include symbols; Release optimizes away easy stepping.

Practices

Run dotnet build -c Debug during development
Set breakpoints on lines; inspect locals and exception details
Use dotnet test to reproduce failures with assertions
Enable analyzers and nullable warnings early—cheaper than runtime-only bugs

Logging vs debugging

Structured logging (ILogger) complements breakpoints in production—this lesson focuses on interactive debugging locally.

Important interview questions and answers

Q: Debug vs Release?
A: Debug includes symbols and fewer optimizations; Release is faster but harder to step through.
Q: Conditional breakpoints?
A: Break only when an expression is true—essential for loops with many iterations.

Self-check

Which build configuration includes full debug symbols?
What CLI command runs automated tests?

Tip: Build Debug locally for symbols—breakpoints map to source lines; Release strips debug info for production.

Interview prep

Debug vs Release?: Debug includes symbols and disables optimizations; Release optimizes for production and strips debug info.
Conditional breakpoints?: Break only when an expression is true—speeds up debugging loops in large datasets.

Interview tip Lesson completion confidence

Can you explain this lesson in 30 seconds without reading notes?

Self-reflection (saved on this device)

Not saved yet.

Playground

Runs on the configured server runner (dev: npm run runner with LEARNING_RUNNER_ENABLED=true). Output appears below the editor.

Code runner not available

Server runner is disabled. Set LEARNING_RUNNER_ENABLED=true and LEARNING_RUNNER_URL in .env (see .env.example).

Check yourself

Multiple choice — immediate feedback.

Discussion

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Starter discussion topics

Debugger attach?
Conditional breakpoint?

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