CA1847: Use string.Contains(char) instead of string.Contains(string) with single characters
Property | Value |
---|---|
Rule ID | CA1847 |
Title | Use string.Contains(char) instead of string.Contains(string) with single characters |
Category | Performance |
Fix is breaking or non-breaking | Non-breaking |
Enabled by default in .NET 8 | As suggestion |
Cause
string.Contains(string)
is used when string.Contains(char)
was available.
Rule description
When searching for a single character, using string.Contains(char)
offers better performance than string.Contains(string)
.
How to fix violations
In general, the rule is fixed simply by using a char literal instead of a string literal.
public bool ContainsLetterI()
{
var testString = "I am a test string.";
return testString.Contains("I");
}
Public Function ContainsLetterI() As Boolean
Dim testString As String = "I am a test string."
Return testString.Contains("I")
End Function
This code can be changed to use a char literal instead.
public bool ContainsLetterI()
{
var testString = "I am a test string.";
return testString.Contains('I');
}
Public Function ContainsLetterI() As Boolean
Dim testString As String = "I am a test string."
Return testString.Contains("I"c)
End Function
When to suppress warnings
Suppress a violation of this rule if you're not concerned about the performance impact of the search invocation in question.
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 CA1847
// The code that's violating the rule is on this line.
#pragma warning restore CA1847
To disable the rule for a file, folder, or project, set its severity to none
in the configuration file.
[*.{cs,vb}]
dotnet_diagnostic.CA1847.severity = none
For more information, see How to suppress code analysis warnings.
See also
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