.NET 10 Performance: SearchValues

In .NET 8, Microsoft introduced SearchValues<T>, a specialized type that optimized searching for a set of values (like bytes or chars) within a span. It vectorized the search, making it significantly faster than IndexOfAny.

In .NET 10, this power has been extended to strings. SearchValues<string> allows you to search for multiple substrings simultaneously with incredible performance.

The Use Case: Parsing and Filtering

Imagine you are writing a parser or a sanitizer that needs to check if a text contains any of a specific list of forbidden words or tokens.

The Old Way (Slow)

private static readonly string[] Forbidden = { "drop", "delete", "truncate" };

public bool ContainsSqlInjection(ReadOnlySpan<char> input)
{
    foreach (var word in Forbidden)
    {
        if (input.Contains(word, StringComparison.OrdinalIgnoreCase))
            return true;
    }
    return false;
}

This is O(N * M) where N is input length and M is the number of words. It scans the string repeatedly.

The New Way: SearchValues

With .NET 10, you can pre-compute the search strategy.

using System.Buffers;

// 1. Create the optimized searcher (do this once, statically)
private static readonly SearchValues<string> SqlTokens = 
    SearchValues.Create(["drop", "delete", "truncate"], StringComparison.OrdinalIgnoreCase);

public bool ContainsSqlInjection(ReadOnlySpan<char> input)
{
    // 2. Search for ANY of them in one pass
    return input.ContainsAny(SqlTokens);
}

Performance Impact

Under the hood, SearchValues.Create analyzes the patterns.

• If they share common prefixes, it builds a trie-like structure.
• It uses Aho-Corasick or Teddy algorithms depending on the pattern density.
• It leverages SIMD (AVX-512) to match multiple characters in parallel.

For a set of 10-20 keywords, SearchValues can be 50x faster than a loop or a Regex.

Finding the Location

You aren’t limited to a boolean check. You can find where the match occurred:

int index = input.IndexOfAny(SqlTokens);
if (index >= 0)
{
    Console.WriteLine($"Found distinct token at index {index}");
}

Summary

SearchValues<string> in .NET 10 brings high-performance text searching to the masses without requiring external libraries. If you are doing any kind of text processing, log analysis, or security filtering, replace your foreach loops with SearchValues immediately.