VB.net 线程安全方法添加列表视图子项？答案

【问题标题】：VB.net Thread safe method to add a listview subitem?VB.net 线程安全方法添加列表视图子项？
【发布时间】：2016-01-09 19:57:57
【问题描述】：

我正在尝试以线程安全的方式将子项添加到列表视图。

在单线程应用程序中，它的工作方式如下：

    For i As Integer = 0 to lvMembers.Items.Count - 1
    Dim lv As ListViewItem = lvMembers.Items(i)
    Dim str As String = lv.Text.ToString
    If str.Contains("value")
    lv.SubItems.Add("OK")
    lv.SubItems(0).ForeColor = Color.Green

    Else
    lv.SubItems.Add("FAILED")
    lv.SubItems(0).ForeColor = Color.Red

    End If
    Next

但是，如果在另一个线程中运行，则会导致跨线程错误。

我查看了使用 Invoke 的委托子示例，但我所看到的所有示例都涉及更新对象的文本属性，我无法理解如何应用该概念以实际将子项添加到列表视图.

非常感谢任何帮助。

【问题讨论】：

我没有看到问题。你能发布你如何使用委托吗？
我的问题是，如果我在主 UI 线程以外的任何地方运行它，它会引发跨线程异常。如果在第二行失败，那么我想我将不得不改变我的整个方法，但不知道从哪里开始。

标签： vb.net listview thread-safety

【解决方案1】：

将新 ListViewItem 添加到 ListView 的线程安全简化方法：

Private Sub AddListViewItem(ByVal name As String, ByVal subitem1 As String, ByVal subitem2 As String)
    ListView1.BeginInvoke(Sub()
                              Dim lvi As New ListViewItem(name)
                              lvi.SubItems.Add(subitem1)
                              lvi.SubItems.Add(subitem2)
                              ListView1.Items.AddRange(New ListViewItem() {lvi})
                          End Sub)
End Sub

【讨论】：

【解决方案2】：

这是一个我自己反复使用的例子。它支持传递变量。我在这个例子中的列表视图有 1 个项目和 2 个子项目（站点、组、pagerank），所以修改它以供您自己使用：

委托人：

Private Delegate Sub ListViewAddItem_delegate(ByVal name As String, ByVal group As String, ByVal pagerank As String)
Private Sub ListViewAddItem(ByVal name As String, ByVal group As String, ByVal pagerank As String)
    If Me.ListView1.InvokeRequired Then
        Dim d As New ListViewAddItem_delegate(AddressOf ListViewAddItem)
        Me.ListView1.BeginInvoke(d, {name, group, pagerank})
    Else
        Dim lvi As New ListViewItem(name)
        lvi.SubItems.Add(group)
        lvi.SubItems.Add(pagerank)
        ListView1.Items.AddRange(New ListViewItem() {lvi})
        ListView1.Update()
    End If
End Sub

如何称呼它：

Dim Name as string = "Test"
Dim Group As String = "TestGroup"
Dim PR As String = "10"
ListViewAddItem(Name, Group, PR)

我在调用 ListViewAddItem() 时添加了“dim xxx as string”只是为了表明 Name Group PR 是字符串

我注意到没有选择任何答案。帮我们大家一个忙，然后选择一个！谢谢！

【讨论】：

【解决方案3】：

一个简单的例子

Public Class Form1

    Private Sub Form1_Load(ByVal sender As System.Object, _
                           ByVal e As System.EventArgs) Handles MyBase.Load

        'sample data for the ListView
        Dim ipsumA() As String = New String() {"Lorem", "ipsum", "dolor", "sit", _
                                               "amet", "consectetur", "adipisicing", _
                                               "elit", "sed", "do", "eiusmod", _
                                               "tempor", "incididunt", "ut", "labore", _
                                               "et", "dolore", "magna", "aliqua", "Ut", _
                                               "enim", "ad", "minim", "veniam", "quis", _
                                               "nostrud", "exercitation", "ullamco", _
                                               "laboris", "nisi", "ut", "aliquip", "ex", _
                                               "ea", "commodo", "consequat", "Duis", "aute", _
                                               "irure", "dolor", "in", "reprehenderit", "in", _
                                               "voluptate", "velit", "esse", "cillum", "dolore", _
                                               "eu", "fugiat", "nulla", "pariatur", "Excepteur", _
                                               "sint", "occaecat", "cupidatat", "non", "proident", _
                                               "sunt", "in", "culpa", "qui", "officia", "deserunt", _
                                               "mollit", "anim", "id", "est", "laborum"}

        Dim lvi As New List(Of ListViewItem)

        For Each s As String In ipsumA
            Dim nLVI As New ListViewItem(s)
            lvi.Add(nLVI)
        Next

        ListView1.Items.AddRange(lvi.ToArray)

        'colorize from another thread
        Dim t As New Threading.Thread(AddressOf thrd)
        t.Start()

    End Sub

    Private Sub thrd()
        If ListView1.InvokeRequired Then
            ListView1.BeginInvoke(New MethodInvoker(AddressOf thrd))
        Else
            For i As Integer = 0 To ListView1.Items.Count - 1
                Dim lv As ListViewItem = ListView1.Items(i)
                Dim str As String = lv.Text.ToString
                If str.ToLower.Contains("ut") Then
                    lv.SubItems.Add("OK")
                    lv.SubItems(0).ForeColor = Color.Green

                Else
                    lv.SubItems.Add("FAILED")
                    lv.SubItems(0).ForeColor = Color.Red
                End If
            Next
        End If
    End Sub
End Class

【讨论】：

【解决方案4】：

Private delegate sub deladdtolist

Private sub addtolist
  If InvokeRequired Then
    del.Invoke( new deladdtolist(AddressOf addtolist))
  else
    For i As Integer = 0 to lvMembers.Items.Count - 1
    Dim lv As ListViewItem = lvMembers.Items(i)
    Dim str As String = lv.Text.ToString
    If str.Contains("value")
    lv.SubItems.Add("OK")
    lv.SubItems(0).ForeColor = Color.Green

    Else
    lv.SubItems.Add("FAILED")
    lv.SubItems(0).ForeColor = Color.Red

    End If
    Next
  End If 
End Sub

【讨论】：