Code Inspection: [ThreadStatic] doesn't work with instance fields

The ThreadStaticAttribute makes a field thread-local. This means that every thread has its own reference corresponding to the field. Fields marked with ThreadStaticAttribute must be static and not initialized statically.

This attribute does not affect instance fields. If you need a thread-local instance field you can use the ThreadLocal<> type that has been introduced in .NET 4.0.

If a static field has an initializer, this initializer is invoked only once - on the thread that executes the static constructor. If initialization on all threads is needed, then the field can be encapsulated by a lazy-initialized property:

[ThreadStatic]
private static object myFoo;
public static object Foo
{
  get
  {
    if (myFoo == null)
      myFoo = new object();
    return myFoo;
  }
}
            

<ThreadStatic>
Private Shared Dim myFoo As Object
Public Shared ReadOnly Property Foo As Object
  Get
    If (myFoo Is Nothing) Then myFoo = New Object()
    Return myFoo
  End Get
End Property
            

Alternatively, the ThreadLocal<>class can be used (as of .NET 4.0):

private ThreadLocal<object> myFoo = new ThreadLocal<object>(() => new object());
            

Dim myFoo As ThreadLocal(Of Object) = new ThreadLocal(Of Object)(Function() New Object())
            

Last modified: 07 April 2022