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CA2259: Ensure ThreadStatic is only used with static fields

  • Article
Property Value
Rule ID CA2259
Title Ensure ThreadStatic is only used with static fields
Category Usage
Fix is breaking or non-breaking Non-breaking
Enabled by default in .NET 9 As warning

Cause

The ThreadStaticAttribute attribute is applied to an instance field.

Rule description

ThreadStaticAttribute, which indicates that the value of a field is unique for each thread, only affects static (Shared in Visual Basic) fields. When applied to instance fields, the attribute has no impact on behavior.

How to fix a violation

To fix a violation, remove the ThreadStaticAttribute attribute from the field.

Example

The following code snippet shows a violation of CA2259:

class C
{
    [ThreadStatic]
    public int number = 404;
}

Class C
    <ThreadStatic>
    Public number As Integer = 404
End Class

When to suppress warnings

It's safe to suppress a warning from this rule. However, the [ThreadStatic] attribute is a nop and isn't doing what you intended it to do.

See also