dotnet-csharp-type-design-performance

Choosing between a struct and a class in C# depends on size, lifetime, and identity. Structs avoid heap allocation overhead for small, short-lived data, while classes are better for larger objects requiring reference semantics and shared mutability.

Using a readonly struct in .NET eliminates defensive copies when passing value types to methods. This ensures immutability while reducing unnecessary memory allocations and CPU overhead during high-frequency calculations.

Ref structs and Span<T> optimize memory access by enabling stack-allocated or contiguous data manipulation without heap allocations. This minimizes garbage collection pressure and improves throughput for high-performance data processing.

Choose FrozenDictionary for immutable, lookup-heavy data created once, ConcurrentDictionary for thread-safe concurrent updates, and ImmutableDictionary for immutable updates. Dictionary remains the standard for general-purpose mutable key-value storage.

Type design directly impacts memory allocation costs in .NET 8.0 applications. Selecting appropriate structs, readonly structs, or ref structs minimizes heap allocations, reduces garbage collection cycles, and lowers overall copy costs.

Ref structs in C# are confined to the stack and cannot be boxed, stored as fields in classes, or used across async boundaries. These limitations ensure safe memory access but restrict their use to narrow, high-performance scopes.