在 VB.NET 中创建一个新线程

Create a new thread in VB.NET

提问by Matt9Atkins

I am trying to create a new thread using an anonymous function but I keep getting errors. Here is my code:

我正在尝试使用匿名函数创建一个新线程，但我不断收到错误消息。这是我的代码：

New Thread(Function() 
    // Do something here
End Function).Start

Here are the errors I get:

以下是我得到的错误：

New:

新的：

Syntax Error

语法错误

End Function:

结束函数：

'End Function' must be preceded by a matching 'Function'.

'End Function' 前面必须有一个匹配的 'Function'。

回答by MrMDavidson

There's two ways to do this;

有两种方法可以做到这一点；

1. With the AddressOfoperator to an existing method

   Sub MyBackgroundThread()
     Console.WriteLine("Hullo")
   End Sub
   

   And then create and start the thread with;

   Dim thread As New Thread(AddressOf MyBackgroundThread)
   thread.Start()
   

2. Or as a lambda function.

   Dim thread as New Thread(
     Sub() 
       Console.WriteLine("Hullo")
     End Sub
   )
   thread.Start()
   

1. 使用AddressOf操作符对现有方法进行操作

   Sub MyBackgroundThread()
     Console.WriteLine("Hullo")
   End Sub
   

   然后创建并启动线程；

   Dim thread As New Thread(AddressOf MyBackgroundThread)
   thread.Start()
   

2. 或者作为 lambda 函数。

   Dim thread as New Thread(
     Sub() 
       Console.WriteLine("Hullo")
     End Sub
   )
   thread.Start()
   

回答by Hans Passant

It is called a lambda expressionin VB. The syntax is all wrong, you need to actually declare a variable of type Thread to use the New operator. And the lambda you create must be a valid substitute for the argument you pass to the Thread class constructor. None of which take a delegate that return a value so you must use Sub, not Function. A random example:

它在 VB 中称为lambda 表达式。语法全错了，你需要实际声明一个 Thread 类型的变量才能使用 New 运算符。您创建的 lambda 必须是您传递给 Thread 类构造函数的参数的有效替代品。其中没有一个接受返回值的委托，因此您必须使用 Sub，而不是 Function。一个随机的例子：

Imports System.Threading

Module Module1

    Sub Main()
        Dim t As New Thread(Sub()
                                Console.WriteLine("hello thread")
                            End Sub)
        t.Start()
        t.Join()
        Console.ReadLine()
    End Sub

End Module

回答by IvanH

What is called has to be a functinon not a sub.

所谓的必须是函数而不是子函数。

Single line(has to return value):

单行（必须返回值）：

Dim worker As New Thread(New ThreadStart(Function() 42))

Multiline:

多行：

Dim worker As New Thread(New ThreadStart(Function()
                                                     ' Do something here
                                                 End Function))

Source: Threading, Closures, and Lambda Expressions in VB.Net

来源：VB.Net 中的线程、闭包和 Lambda 表达式