ThreadStaticAttribute 类

定义

public ref class ThreadStaticAttribute : Attribute

[System.AttributeUsage(System.AttributeTargets.Field, Inherited=false)]
public class ThreadStaticAttribute : Attribute

[System.AttributeUsage(System.AttributeTargets.Field, Inherited=false)]
[System.Serializable]
public class ThreadStaticAttribute : Attribute

[System.AttributeUsage(System.AttributeTargets.Field, Inherited=false)]
[System.Serializable]
[System.Runtime.InteropServices.ComVisible(true)]
public class ThreadStaticAttribute : Attribute

[<System.AttributeUsage(System.AttributeTargets.Field, Inherited=false)>]
type ThreadStaticAttribute = class
    inherit Attribute

[<System.AttributeUsage(System.AttributeTargets.Field, Inherited=false)>]
[<System.Serializable>]
type ThreadStaticAttribute = class
    inherit Attribute

[<System.AttributeUsage(System.AttributeTargets.Field, Inherited=false)>]
[<System.Serializable>]
[<System.Runtime.InteropServices.ComVisible(true)>]
type ThreadStaticAttribute = class
    inherit Attribute

Public Class ThreadStaticAttribute
Inherits Attribute

继承

Object

Attribute

ThreadStaticAttribute

属性

AttributeUsageAttribute SerializableAttribute ComVisibleAttribute

示例

下面的示例代码演示如何使用 ThreadStaticAttribute 来确保静态字段对每个线程是唯一的。 在代码中，每个线程向线程静态字段分配不同的请求 ID，然后模拟跨多个方法调用的请求处理。

using System;
using System.Threading;

class Program
{
    [ThreadStatic]
    private static string? _requestId;

    static void Main()
    {
        Thread thread1 = new(ProcessRequest);
        Thread thread2 = new(ProcessRequest);

        thread1.Start("REQ-001");
        thread2.Start("REQ-002");

        thread1.Join();
        thread2.Join();

        Console.WriteLine("Main thread execution completed.");
    }

    static void ProcessRequest(object? requestId)
    {
        // Assign the request ID to the thread-static field.
        _requestId = requestId as string;

        // Simulate request processing across multiple method calls.
        PerformDatabaseOperation();
        PerformLogging();
    }

    static void PerformDatabaseOperation()
    {
        Console.WriteLine($"Thread {Environment.CurrentManagedThreadId}: Processing DB operation for request {_requestId}");
    }

    static void PerformLogging()
    {
        Console.WriteLine($"Thread {Environment.CurrentManagedThreadId}: Logging request {_requestId}");
    }
}

open System
open System.Threading

type ThreadLocal() =
    [<ThreadStatic; DefaultValue>]
    static val mutable private requestId: string option

    static member PerformLogging() =
        Console.WriteLine($"Thread {Environment.CurrentManagedThreadId}: Logging request {ThreadLocal.requestId.Value}")

    static member PerformDatabaseOperation() =
        Console.WriteLine($"Thread {Environment.CurrentManagedThreadId}: Processing DB operation for request {ThreadLocal.requestId.Value}")

    static member ProcessRequest(reqId: obj) =
        ThreadLocal.requestId <- Some(reqId :?> string)
        ThreadLocal.PerformDatabaseOperation()
        ThreadLocal.PerformLogging()

[<EntryPoint>]
let main _ =
    let thread1 = Thread(ThreadStart(fun () -> ThreadLocal.ProcessRequest("REQ-001")))
    let thread2 = Thread(ThreadStart(fun () -> ThreadLocal.ProcessRequest("REQ-002")))

    thread1.Start()
    thread2.Start()
    thread1.Join()
    thread2.Join()

    Console.WriteLine("Main thread execution completed.")
    0

Imports System
Imports System.Threading

Module Program

    <ThreadStatic>
    Private _requestId As String

    Sub Main()
        Dim thread1 As New Thread(AddressOf ProcessRequest)
        Dim thread2 As New Thread(AddressOf ProcessRequest)

        thread1.Start("REQ-001")
        thread2.Start("REQ-002")

        thread1.Join()
        thread2.Join()

        Console.WriteLine("Main thread execution completed.")
    End Sub

    Sub ProcessRequest(ByVal requestId As Object)
        ' Assign the request ID to the thread-static field
        _requestId = requestId.ToString()

        ' Simulate request processing across multiple method calls
        PerformDatabaseOperation()
        PerformLogging()
    End Sub

    Sub PerformDatabaseOperation()
        Console.WriteLine($"Thread {Environment.CurrentManagedThreadId}: Processing DB operation for request {_requestId}")
    End Sub

    Sub PerformLogging()
        Console.WriteLine($"Thread {Environment.CurrentManagedThreadId}: Logging request {_requestId}")
    End Sub

End Module

注解

static标记的ThreadStaticAttribute字段在线程之间不共享。 每个执行线程都有一个单独的字段实例，并独立设置并获取该字段的值。 如果在不同的线程上访问该字段，它将包含不同的值。

除了将 ThreadStaticAttribute 属性应用于字段之外，还必须将其定义为 static（在 C# 或 F# 中）或 Shared（Visual Basic）。

按原样使用此属性，不派生自它。

有关使用属性的详细信息，请参阅 “属性”。

另请参阅

• Attribute
• Thread
• AsyncLocal<T>
• 使用属性 扩展元数据
• 托管线程