Cause

AnIndexOfAny orContainsAny method is called with many constant values in a way that can benefit from usingSearchValues instead.

The rule doesn't flag calls that use up to five values, as those already use an optimal implementation.

Rule description

Using a cachedSearchValues<T> instance is more efficient than passing values toIndexOfAny orContainsAny directly.

How to fix violations

Create and cache aSearchValues<T> instance in astatic readonly field, then pass that instance to theIndexOfAny orContainsAny call instead.

Acode fix that automatically performs this transformation is available.

Example

The following code snippet shows two violations of CA1870:

static readonly char[] MyValues = new[] { 'a', 'b', 'c', 'x', 'y', 'z' };static int IndexOfMyValues(ReadOnlySpan<char> text){    return text.IndexOfAny(MyValues);}static bool ContainsOnlyMyValues(ReadOnlySpan<char> text){    return !text.ContainsAnyExcept("abcxyz");}

The following code snippet fixes the violations:

private static readonly SearchValues<char> s_myValues = SearchValues.Create("abcxyz");static int IndexOfMyValues(ReadOnlySpan<char> text){    return text.IndexOfAny(s_myValues);}static bool ContainsOnlyMyValues(ReadOnlySpan<char> text){    return !text.ContainsAnyExcept(s_myValues);}

If there are multiple calls toIndexOfAny with the same set of values,s_myValues should be reused.

When to suppress warnings

It's safe to suppress this warning if performance isn't a concern.

Suppress a warning

If you just want to suppress a single violation, add preprocessor directives to your source file to disable and then re-enable the rule.

#pragma warning disable CA1870// The code that's violating the rule is on this line.#pragma warning restore CA1870

To disable the rule for a file, folder, or project, set its severity tonone in theconfiguration file.

[*.{cs,vb}]dotnet_diagnostic.CA1870.severity = none

For more information, seeHow to suppress code analysis warnings.