VB.Net: 将一个列表的内容放入另一个列表

Question

给定两个列表：

Dim listOfCollectiveTasks As New List(Of String) Dim listOfCollectiveTasks2 As New List(Of String)

我正在向 listOfCollectiveTasks2 添加元素，然后尝试删除 listOfCollectiveTasks 的内容...然后将 listOfCollectiveTasks2 的内容放入其中。

代码：

Public Sub testRecursive()
    For Each atask In listOfCollectiveTasks
        getRemainingSupportingTask(getTaskID(atask), "Collective")
        'getRemainingSupportingTask(atask, "Individual")
    Next


    listOfCollectiveTasks = Nothing
    For Each item In listOfCollectiveTasks2
        Console.WriteLine(item.ToString)
    Next
    listOfCollectiveTasks.Concat(listOfCollectiveTasks2)
    testRecursive()

End Sub

Public Sub getRemainingSupportingTask(theID As String, collectiveOrSupporting As String)
    Dim rs As New ADODB.Recordset
    Dim listOfTasks As New List(Of String)
    Dim theQuery As String = "Select * from [SupportingTask$] where [TaskID] = "
    theQuery = theQuery + "'" + theID + "'" + " and [SupportingTaskTypeName] = " + "'" + collectiveOrSupporting + "'"
    rs = MyADO.executeQuery(theQuery)
    Console.WriteLine(theQuery)


    Do Until rs.EOF
        Dim theString As String = rs.Fields("SupportingTaskNumber").Value
        If String.Equals(collectiveOrSupporting, "Collective") Then

            listOfCollectiveTasks2.Add(theString)



            Console.WriteLine(theString)
            newXlSheet.Cells(lastCollectiveRow, 1) = theString
            lastCollectiveRow = lastCollectiveRow + 1


        Else
            'listOfIndividualTasks.Add(theString)
            Console.WriteLine(theString)
            newXlSheet.Cells(lastIndividualRow, 2) = theString
            lastIndividualRow = lastIndividualRow + 1

        End If
        rs.MoveNext()
    Loop
    Console.WriteLine("Done")
    Console.WriteLine("")



End Sub

我在 `listOfCollectiveTasks.Concat(listOfCollectiveTasks2) 上收到 System.ArgumentNullException。我想不出将 list2 中的项目放入 list1 的方法。

Answer 1

除非您必须在市场之后或市场操作之前做一些事情，否则只添加一个包含 System.Type 集合的范围会更有效。然后清除追加的原始列表。像这样：

Sub Main()
    Dim ls1 = New List(Of String)({"a", "b", "c", "d"})
    Dim ls2 = New List(Of String)
    Dim ls3 = New List(Of String)({"e", "f"})

    ls2.AddRange(ls1)
    ls1.Clear()

    ls2.AddRange(ls3)
    ls3.Clear()

    Console.WriteLine($"Count of List1: {ls1.Count}")
    Console.WriteLine($"Count of List2: {ls2.Count}")
    Console.WriteLine($"Count of List3: {ls3.Count}")
    ls2.ForEach(Sub(x) Console.WriteLine(x))

    Console.ReadLine()
End Sub

VB.Net: 将一个列表的内容放入另一个列表

VB.Net: Putting Contents of One List into Another

vb.net

recursion

for-loop

list

instantiation