.net - 将多个参数传递给多个线程

Question

我有一个创建多个线程的循环:

SomeClass..

Dim someNumber As Integer = 0
Dim somethingElse As Integer = 10
Dim myThread(500) As System.Threading.Thread

For i As Integer = 0 To 500
    someNumber += 1
    somethingElse += 10

    myThread(i) = New Thread(Sub() myThreadFunction(someNumber, somethingElse))
    myThread(i).Start()
Next

For j As Integer = 0 To 500
    myThread(j).Join()
Next

Sub myThreadFunction(ByVal someNumber As Integer, ByRef somethingElse As Integer)

    DoStuff

End Sub

现在我的问题是有时我将错误的值传递给 myThreadFunction，通常是应该在循环的下一次迭代中传递的值。

我是不是做错了什么，还有更好的方法吗？

Answer 1

这是因为 lambda 在错误的范围内关闭了您的变量。 Eric Lippert 在 Closing over the loop variable considered harmful 中详细描述了这个问题。 .

要实现这一点，您需要在适当的范围内引入一个临时变量:

For i As Integer = 0 To 500
    someNumber += 1
    somethingElse += 10

    ' Make some locally scoped variables
    Dim temp1 As Integer = someNumber
    Dim temp2 As Integer = somethingElse 

    ' Use the temporaries
    myThread(i) = New Thread(Sub() myThreadFunction(temp1, temp2))
    myThread(i).Start()
Next

单独说明:我建议还考虑使用 ThreadPool或 Task Parallel Library而不是手动创建线程。通常，对于大多数场景来说，这是一种更好的方法。