试图将本地数据表中的列表框选定项的SUM放入标签

时间：2018-08-28 15:01:12

标签： vb.net winforms visual-studio-2015

我一直在搜索几天，以获取任何可能的参考或建议，而我遇到的一切都没有用。

目标：

用户将在ComboBox1中选择选项，然后确定ComboBox2中的可用选项，然后在ListBox1中填充操作列表。

当用户在ListBox1中选择可用的操作时，我需要输出为标签中显示的值的总和（在这种情况下，以分钟为单位的总时间）。

所使用的数据存储在本地数据库中。到目前为止，一切都适用于我的组合框和列表框。

我试图获取ListBox1中所有选定项的Text值，以将表中的数值（第4列“ OperationsTime”）输出到一个标签中，该标签将显示所有选择的总和（总输入时间分钟）。

我从其他帖子中尝试过的一些事情： 

  1.  Label9.Text = ListBox1.ValueMember

  2.  Label9.Text = ListBox1.ValueMember.ToString

  3.  Label9.Text = CType(ListBox1.SelectedItem, DataRowView).Row.Item("OperationsTime").ToString

尝试使用Double：

         Dim Total As Double = 0
    For Each Time As Integer In ListBox1.SelectedItems
        Total += CDbl(Time.ToString.Substring(Time.ToString.LastIndexOf(",") + 1))
    Next
    Label9.Text = Total.ToString

表格的屏幕截图： Operations Data Table

下面是我的代码： 

Imports System.Data
Imports System.Configuration
Imports System.Data.SqlClient

Public Class MainHome
    Private Function GetData(ByVal sql As String) As DataTable
        Dim constr As String = "Data Source=(LocalDB)\MSSQLLocalDB;AttachDbFilename=C:\Users\hartj\Documents\visual studio 2015\Projects\TIMEMATRIX2.0\TIMEMATRIX2.0\TMX.mdf;Integrated Security=True"
        Using con As SqlConnection = New SqlConnection(constr)
            Using sda As SqlDataAdapter = New SqlDataAdapter(sql, con)
                Dim dt As DataTable = New DataTable()
                sda.Fill(dt)
                Dim row As DataRow = dt.NewRow()
                row(0) = 1
                row(1) = "Please Select"
                dt.Rows.InsertAt(row, 0)
                Return dt
            End Using
        End Using
    End Function

    Private Sub MainHome_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
        ComboBox1.DataSource = Me.GetData("SELECT  SizeId, SizeName FROM Size")
        ComboBox1.DisplayMember = "SizeName"
        ComboBox1.ValueMember = "SizeId"
        ComboBox2.Enabled = False
        ComboBox3.Enabled = False
    End Sub

    Private Sub ComboBox1_SelectionChangeCommitted(sender As Object, e As EventArgs) Handles ComboBox1.SelectionChangeCommitted
        ComboBox2.DataSource = Nothing
        ComboBox3.DataSource = Nothing
        ComboBox2.Enabled = False
        ComboBox3.Enabled = False
        If ComboBox1.SelectedValue.ToString() <> "0" Then
            Dim sql As String = String.Format("SELECT DetailLevelId, DetailLevelName FROM DetailLevel WHERE SizeId = {0}", ComboBox1.SelectedValue)
            ComboBox2.DataSource = Me.GetData(sql)
            ComboBox2.DisplayMember = "DetailLevelName"
            ComboBox2.ValueMember = "DetailLevelId"
            ComboBox2.Enabled = True
        End If
    End Sub

    Private Sub ComboBox2_SelectionChangeCommitted(sender As Object, e As EventArgs) Handles ComboBox2.SelectionChangeCommitted
        ListBox1.DataSource = Nothing
        ListBox1.Enabled = False
        If ComboBox2.SelectedValue.ToString() <> "0" Then
            Dim sql As String = String.Format("SELECT OperationsId, OperationsName, OperationsTime FROM Operations WHERE DetailLevelId = {0}", ComboBox2.SelectedValue)
            ListBox1.DataSource = Me.GetData(sql)
            ListBox1.ValueMember = "OperationsName"
            ListBox1.ValueMember = "OperationsTime"
            ListBox1.Enabled = True

            Label9.Text = CType(ListBox1.SelectedValue, Integer).ToString
            'Label.Text = CType(cbbank.SelectedItem, DataRowView).Row.Item("Account").ToString
        End IF
    End Sub

2 个答案:

答案 0 :(得分：0)

Dim totalOperationsTime As Double

For Each view As DataRowView In ListBox1.SelectedItems
    totalOperationsTime += CDbl(view("OperationsTime"))
Next

无需从DataRow获取DataRowView，因为您可以直接从DataRowView访问字段值。它可以并且确实执行DataRow所做的许多相同的事情。

这是最传统的方式，但是还有其他选择。您可以向其中扔一些LINQ：

Dim totalOperationsTime = ListBox1.SelectedItems.Cast(Of DataRowView)().
                                                 Sum(Function(view) CDbl(view("OperationsTime")))

ValueMember属性只能帮助您获得SelectedItem的值，这有点令人讨厌。这是我前一段时间写的一个类，它添加了一个GetItemValue方法，该方法与ValueMember的{​​{1}}方法一样，充分利用了GetItemText：

DisplayMember

如果您使用该控件而不是常规的Public Class ListBoxEx Inherits ListBox Public Function GetItemValue(item As Object) As Object Dim index = Me.Items.IndexOf(item) If (index <> -1 AndAlso Me.DataManager IsNot Nothing) Then Return Me.FilterItemOnProperty(Me.DataManager.List(index), Me.ValueMember) End If Return Nothing End Function End Class ，则可以执行以下操作：

ListBox

或者这个：

Dim totalOperationsTime As Double

For Each item In ListBoxEx1.SelectedItems
    totalOperationsTime += CDbl(ListBoxEx1.GetItemValue(item))
Next

使用该自定义控件的一个优点是，您不必知道数据源或其项目的类型。您只需要知道Dim totalOperationsTime = ListBox1.SelectedItems.Cast(Of Object)(). Sum(Function(item) CDbl(ListBoxEx1.GetItemValue(item))) 已经设置。

答案 1 :(得分：0)

我对您的代码进行了一些更改。它与ListBox一起使用。有关详细信息，请参见评论。

' "Please Select" doesn't work well in the ListBox, I added it as an option
Private Shared Function GetData(ByVal sql As String, insertPleaseSelect As Boolean) As DataTable
    Dim constr As String = "Data Source=(LocalDB)\MSSQLLocalDB;AttachDbFilename=C:\Users\hartj\Documents\visual studio 2015\Projects\TIMEMATRIX2.0\TIMEMATRIX2.0\TMX.mdf;Integrated Security=True"
    Using con As SqlConnection = New SqlConnection(constr)
        Using sda As SqlDataAdapter = New SqlDataAdapter(sql, con)
            Dim dt As DataTable = New DataTable()
            sda.Fill(dt)
            If insertPleaseSelect Then
                Dim row As DataRow = dt.NewRow()
                row(0) = 1
                row(1) = "Please Select"
                dt.Rows.InsertAt(row, 0)
            End If
            Return dt
        End Using
    End Using
End Function

Private Sub MainHome_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
    ComboBox1.DataSource = GetData("SELECT  [SizeId], [SizeName] FROM [Size]", True)
    ComboBox1.DisplayMember = "SizeName"
    ComboBox1.ValueMember = "SizeId"
    ComboBox2.Enabled = False
    ListBox1.SelectionMode = SelectionMode.MultiSimple ' allow multi-select
End Sub

Private Sub ComboBox1_SelectionChangeCommitted(sender As Object, e As EventArgs) Handles ComboBox1.SelectionChangeCommitted
    ComboBox2.DataSource = Nothing
    ComboBox2.Enabled = False
    If ComboBox1.SelectedValue.ToString() <> "0" Then
        Dim sql As String = String.Format("SELECT [DetailLevelId], [DetailLevelName] FROM [DetailLevel] WHERE [SizeId] = {0}", ComboBox1.SelectedValue)
        ComboBox2.DataSource = GetData(sql, True)
        ComboBox2.DisplayMember = "DetailLevelName"
        ComboBox2.ValueMember = "DetailLevelId"
        ComboBox2.Enabled = True
    End If
End Sub

Private Sub ComboBox2_SelectionChangeCommitted(sender As Object, e As EventArgs) Handles ComboBox2.SelectionChangeCommitted
    ListBox1.DataSource = Nothing
    ListBox1.Enabled = False
    If ComboBox2.SelectedValue.ToString() <> "0" Then
        Dim sql As String = String.Format("SELECT [OperationsId], [OperationsName], [OperationsTime] FROM [Operations] WHERE [DetailLevelId] = {0}", ComboBox2.SelectedValue)
        ListBox1.DataSource = GetData(sql, False)
        ListBox1.DisplayMember = "OperationsName" ' changed this from ValueMember to DisplayMember
        ListBox1.ValueMember = "OperationsTime"
        ListBox1.Enabled = True
        ListBox1.ClearSelected() ' Every time the ListBox is populated, clear it
    End If
End Sub

' Added this handler to respond to user input, not programmatic selection changes
Private Sub ListBox1_Click(sender As Object, e As EventArgs) Handles ListBox1.Click
    ' Here is the sum
    Label9.Text = ListBox1.SelectedItems.OfType(Of DataRowView).Sum(Function(o) CType(o("OperationsTime"), Double))
End Sub
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