Tips and Tricks #129: Use Span for Zero-Allocation String Parsing

Eliminate heap allocations when parsing strings by using Span for memory-efficient operations.

Code Snippet

// Before: Creates new string allocations
string input = "key=value";
string[] parts = input.Split('=');
string key = parts[0];
string value = parts[1];

// After: Zero allocations with Span
ReadOnlySpan span = input.AsSpan();
int index = span.IndexOf('=');
ReadOnlySpan key = span[..index];
ReadOnlySpan value = span[(index + 1)..];

Why This Helps

• Eliminates temporary string allocations in hot paths
• Reduces GC pressure significantly in high-throughput scenarios
• Works seamlessly with existing string APIs

How to Test

• Use BenchmarkDotNet to compare allocation counts
• Profile with dotMemory to verify zero allocations

When to Use

High-frequency parsing operations, API request handling, log processing pipelines.

Performance/Security Notes

Span cannot be used in async methods or stored in class fields. Use Memory for those cases.

References

• https://docs.microsoft.com/en-us/dotnet/api/system.span-1

Try this tip in your next project and share your results in the comments!