等待单实例发生完成，然后继续进行下一行VB.NET

问题描述

当前，我正在VB（.net框架获胜表单）中使用“ make app单一实例”（MyApplication_StartupNextInstance事件）将命令行参数从多个实例传递到主表单。我将其添加到字符串列表，然后将此列表传递给下一个函数/子。如果我在调用下一个函数之前添加一个消息框，则该列表将捕获所有参数，但是如果没有msgBox，则不会捕获所有参数。

我已经厌倦了使用计时器/延迟，这既是命中又是失误。尝试使用定时msgBox，在几秒钟后分拆，这是相同的。如何让它等待所有实例都运行，然后继续执行下一行代码？

'ApplicationEvents.vb
 Private Sub MyApplication_StartupNextInstance(sender As Object,e As applicationservices.StartupNextInstanceEventArgs) Handles Me.StartupNextInstance

            Dim f = Application.MainForm

            If f.GetType Is GetType(my_app_name) Then
                CType(f,my_app_name).NewArgumentsReceived(e.CommandLine(0)) 
            End If

        End Sub


'my app has the below codes

Public Sub NewArgumentsReceived(args As String)
        mylist.Add(args)
      

End Sub


Private Sub SomeForm_Load(sender As Object,e As EventArgs) Handles MyBase.Load

mylist.Add(arg) 'arg is for main form 'args' is for instances

'this is where I want to wait until all the other instances have completed

Anotherfunction(mylist)

End Sub

解决方法

正如我在评论中提到的那样，StartupNextInstance事件可以在任何时间引发，因此您应设计自己的应用以随时对其做出反应。初始实例不知道会有多少个后续实例，或者它们何时开始，因此只要它们发生，就应该一次对它们做出一次反应。这是一个单实例应用程序的示例，其中主要形式是MDI父级，命令行参数是文本文件路径，每个路径都在子窗口中打开。

子窗体：

Imports System.IO

Public Class ChildForm

    Public Property FilePath As String

    Private Sub Form2_Load(sender As Object,e As EventArgs) Handles MyBase.Load
        TextBox1.Text = File.ReadAllText(FilePath)
    End Sub

End Class

父母表格：

Public Class ParentForm

    Private Sub Form1_Load(sender As Object,e As EventArgs) Handles MyBase.Load
        Dim args = Environment.GetCommandLineArgs()

        If args.Length > 1 Then
            LoadChildForm(args(1))
        End If
    End Sub

    Public Sub LoadChildForm(filePath As String)
        Dim child As New ChildForm With {.MdiParent = Me,.FilePath = filePath}

        child.Show()
    End Sub

End Class

应用程序事件：

Imports Microsoft.VisualBasic.ApplicationServices

Namespace My
    ' The following events are available for MyApplication:
    ' Startup: Raised when the application starts,before the startup form is created.
    ' Shutdown: Raised after all application forms are closed.  This event is not raised if the application terminates abnormally.
    ' UnhandledException: Raised if the application encounters an unhandled exception.
    ' StartupNextInstance: Raised when launching a single-instance application and the application is already active. 
    ' NetworkAvailabilityChanged: Raised when the network connection is connected or disconnected.

    Partial Friend Class MyApplication

        Private Sub MyApplication_StartupNextInstance(sender As Object,e As StartupNextInstanceEventArgs) Handles Me.StartupNextInstance
            Dim args = e.CommandLine

            If args.Count > 0 Then
                DirectCast(MainForm,ParentForm).LoadChildForm(args(0))
            End If
        End Sub

    End Class

End Namespace

在这种情况下，初始实例不会等待任何东西。它只是继续前进，并使用其自己的命令行参数执行操作。它不知道是否会有任何后续实例，或者如果有，将有多少实例以及它们何时开始，因此不知道它在等待什么。每当启动另一个实例时，初始实例都会使用提供的命令行参数进行响应。

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