C++ to C# Conversion Cheat Sheet: Syntax Mappings and Tips
Basic syntax mappings
| Concept | C++ | C# |
|---|---|---|
| Namespace / module | namespace MyApp { } | namespace MyApp { } |
| Entry point | int main(int argc, charargv) | static void Main(string[] args) |
| Printing | std::cout << “hi”; | Console.WriteLine(“hi”); |
| Comments | // single-line /* multi-line / | // single-line / multi-line */ |
Types
| C++ | C# | Notes |
|---|---|---|
| int, short, long | int, short, long | sizes differ by platform — prefer C# types |
| unsigned int | uint | Less commonly used in .NET libraries |
| long long | long | C# long = 64-bit |
| float, double | float, double | same names |
| char | char | C# char is UTF-16 |
| string (std::string) | string | Immutable in C#; use StringBuilder for mutations |
| nullptr / NULL | null | C# has nullable reference and value types (T?) |
| bool | bool | same |
Memory and ownership
- No manual delete: C# uses garbage collection; remove delete/new pairings and unmanaged pointer ownership.
- Pointers: Avoid pointers; use safe references. Use unsafe blocks only when necessary.
- RAII: Replace C++ destructors with IDisposable and using statements.
Classes, structs, and members
| C++ | C# |
|---|---|
| class/struct (default private/public depends) | class (reference), struct (value) |
| Constructors / Destructors | Constructors; use IDisposable for cleanup |
| Access specifiers | public / protected / private / internal (C#) |
| Inheritance | single inheritance + interfaces |
| Virtual methods | virtual / override |
Methods and properties
- Method declaration: returnType Name(params) { }
- Properties: Prefer C# properties over getter/setter methods.
- C++: int getX(); void setX(int);
- C#: public int X { get; set; }
Templates → Generics
- C++ templates → C# generics: template -> class MyClass
- No template metaprogramming equivalent; use reflection, generics, or source generators.
Error handling
- C++ error codes / exceptions -> C# exceptions.
- Prefer exceptions; use try/catch/finally and IDisposable for cleanup.
Standard library mappings
| C++ STL | .NET |
|---|---|
| std::vector | List |
| std::map | Dictionary |
| std::unorderedmap | Dictionary |
| std::string | string |
| std::thread | Thread / Task (use Task and async/await) |
| std::mutex | lock (Monitor) / Mutex |
| std::chrono | TimeSpan / DateTime / Stopwatch |
Concurrency
- Prefer Task, async/await, and higher-level constructs (Task.Run, Parallel.For).
- Use lock(obj) for critical sections.
- Avoid manual thread management when possible.
Interop and unsafe code
- P/Invoke replaces many native interop needs.
- Use unsafe and fixed for pointer operations; prefer Span and Memory for performance.
Common pitfalls
- Assuming identical performance characteristics; garbage collection and runtime differ.
- Not converting ownership/cleanup semantics (memory/resource leaks or premature disposal).
- Differences in integer sizes and signed/unsigned behavior.
- Implicit conversions and operator overloading differences.
Migration tips
- Start with design—map architecture, not line-by-line.
- Replace STL containers with .NET collections.
- Convert classes, then APIs, then internals.
- Add unit tests to validate behavior during migration.
- Use automated tools (e.g., code converters) for boilerplate, but review manually.
- Incrementally run and profile to catch semantic/performance issues.
Quick reference: small examples
C++:
cpp
class Point { public: int x; int y; Point(int x,int y): x(x), y(y) {} int Sum() { return x + y; } };
C#:
csharp
public class Point { public int X { get; set; } public int Y { get; set; } public Point(int x,int y) { X = x; Y = y; } public int Sum() => X + Y; }
If you want, I can generate a one-page printable cheat sheet or convert a specific C++ snippet to C#.
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