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CA1309: Use ordinal StringComparison

  • Article
Property Value
Rule ID CA1309
Title Use ordinal StringComparison
Category Globalization
Fix is breaking or non-breaking Non-breaking
Enabled by default in .NET 9 No

Cause

A string comparison operation that is nonlinguistic does not set the StringComparison parameter to either Ordinal or OrdinalIgnoreCase.

Rule description

Many string operations, most importantly the System.String.Compare and System.String.Equals methods, now provide an overload that accepts a System.StringComparison enumeration value as a parameter.

When you specify either StringComparison.Ordinal or StringComparison.OrdinalIgnoreCase, the string comparison is non-linguistic. That is, the features that are specific to the natural language are ignored when comparison decisions are made. Ignoring natural language features means the decisions are based on simple byte comparisons and not on casing or equivalence tables that are parameterized by culture. As a result, by explicitly setting the parameter to either the StringComparison.Ordinal or StringComparison.OrdinalIgnoreCase, your code often gains speed, increases correctness, and becomes more reliable.

How to fix violations

To fix a violation of this rule, change the string comparison method to an overload that accepts the System.StringComparison enumeration as a parameter, and specify either Ordinal or OrdinalIgnoreCase. For example, change String.Compare(str1, str2) to String.Compare(str1, str2, StringComparison.Ordinal).

When to suppress warnings

It is safe to suppress a warning from this rule when the library or application is intended for a limited local audience, or when the semantics of the current culture should be used.

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.

C# 
#pragma warning disable CA1309
// The code that's violating the rule is on this line.
#pragma warning restore CA1309

To disable the rule for a file, folder, or project, set its severity to none in the configuration file.

ini 
[*.{cs,vb}]
dotnet_diagnostic.CA1309.severity = none

For more information, see How to suppress code analysis warnings.

See also