当列表框包含从保存文件加载的项目时，防止将重复项添加到列表框的问题

Question

我遇到了阻止将重复项添加到列表框的问题。

我的 Windows 表单有 2 个列表框
表单设计为当用户单击按钮时，他们在第一个框中选中的项目将添加到第二个框中
下面我添加到 "add" 按钮的代码旨在防止在框 2 中已存在相同项目的情况下将框 1 中选中的项目添加到框 2。
我的代码的问题是，如果方框 2 包含从保存文件加载的项目，它不会阻止重复项被添加到方框 2。

关于如何解决这个问题有什么想法吗？

    Public Sub additems_Click(sender As Object, e As EventArgs) Handles additems.Click

    Dim itemChecked As Object
    Dim alreadyonkey As Boolean
    Dim duplicates As Integer = 0       

   If box1.CheckedItems.Count > 0 Then
        For Each itemChecked In box1.CheckedItems
            alreadyadded = False
            'Check if item selected has already been added to box2
            If box2.Items.Contains(itemChecked) = True Then
                alreadyadded = True
                duplicates = duplicates + 1
            Else
                alreadyadded = False
            End If

            'Add item if all criteria met
            If box2.Items IsNot "" And alreadyadded = False Then
                box2.Items.Add(itemChecked)
            End If
        Next

        If duplicates > 0 Then
            MsgBox("One or more of the items you are trying to add have already been added.", MsgBoxStyle.Critical, "Item has already been added")
            alreadyadded = False
        End If
    End If

结束子

Answer 1

我发现了我的代码的问题...这个问题主要是因为需要使用嵌套的 For Each 循环来一次比较 box1 中的每个项目和 box2 中的每个项目，并且需要将项目发送到字符串变量并使用 "String.Equals".

进行比较

Public Sub additems_Click(sender As Object, e As EventArgs) Handles additems.Click

    Dim itemChecked As Object
    Dim alreadyadded As Boolean
    Dim duplicates As Integer = 0


    If box1.CheckedItems.Count > 0 
        For Each itemChecked In box1.CheckedItems
            Dim itemtoadd As String = itemChecked.ToString

            'Check if item selected has already been added to box2
            For Each item In box2.Items
                Dim box2item As String = item.ToString

                If String.Equals(Trim(itemtoadd), Trim(box2item)) = True Then
                    alreadyadded = True
                    duplicates = duplicates + 1
                Else

                End If
            Next

            'Add item if all criteria met
            If itemChecked IsNot "" And alreadyadded = False Then
                box2.Items.Add(itemChecked)
            End If
        Next


        If duplicates > 0 Then
            MsgBox("One or more of the items you are trying to add have already been added.", MsgBoxStyle.Critical, "Item hase already been added")
            alreadyadded = False
            duplicates = 0
        End If
    End If

当列表框包含从保存文件加载的项目时，防止将重复项添加到列表框的问题

Issue Preventing Duplicates from Being Added to a Listbox When Listbox Contains Items Loaded from a Save File

vb.net

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listbox

checkedlistbox

listboxitems