CA2265: Do not compare `Span<T>` to `null` or `default`

#Cause

A System.Span instance is compared to null or default.

#Rule description

Comparing a span to null or default might not do what you intended. default and the null literal are implicitly converted to Span<T>.Empty.

#How to fix violations

Remove the redundant comparison or make the code more explicit by calling System.Span.IsEmpty instead.

#Example

The following code snippet shows two violations of CA2265 and the fix for the violations.

sample · csharpdocs/fundamentals/code-analysis/quality-rules/snippets/csharp/all-rules/ca2265.cs1

using System;

namespace ca2265;
class CA2265
{
    public static void RunIt()
    {
        // <Snippet1>
        Span<int> span = new([1, 2, 3]);
        // CA2265 violation.
        if (span == null) { }
        // CA2265 violation.
        if (span == default) { }

        // Fixes the violation.
        if (span.IsEmpty) { }
        // </Snippet1>
    }
}

#When to suppress warnings

It's safe to suppress this warning if you meant to compare the span to the empty span.

#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 CA2265
// The code that's violating the rule is on this line.
#pragma warning restore CA2265

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

[*.{cs,vb}]
dotnet_diagnostic.CA2265.severity = none

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

#See also

• dotnet/runtime issue 84265