组合框未使用 bindingnavigator 记录选择器显示下一条记录答案

【问题标题】：Comboboxes are not showing the next record using the bindingnavigator record selector组合框未使用 bindingnavigator 记录选择器显示下一条记录
【发布时间】：2019-07-25 01:12:41
【问题描述】：

我正在使用一个 Winforms 应用程序，它有一个多选项卡式表单，它链接到 Visual Studio Community 2017 中的 MySQL 数据库。该表单具有 bindingsource 和 bindingnavigator 控件。我的基本数据库结构如下：-

用品

供应 ID (pk) 供应名称

年

年份 ID (pk) 年号

颜色

颜色 ID (pk) 颜色名称

订单

订单 ID (pk) 订单名称 SupplyID_fk (fk) CatalogID_fk (fk) YearID_fk (fk) ColourID_fk (fk)

Orders 表中有四个组合框：CboSupplyID_fk、CboCatalogID_fk、CboYearID_fk 和 CboColourID_fk。我的问题是，当我尝试使用 bindingnavigator 记录选择器导航到下一条记录时（CboColourID_fk 除外，它工作正常）。 vb.net代码如下图：-

Imports MySql
Imports MySql.Data.MySqlClient
Imports MySql.Data

Public Class Form1
    Inherits Form

Dim cbCatalog As New MySqlCommandBuilder(daCatalog)
Dim cbYears As New MySqlCommandBuilder(daYears)
Dim cbOrderTypes As New MySqlCommandBuilder(daOrderTypes)
Dim cbOrderColours As New MySqlCommandBuilder(daOrderColours)
Dim dsCatalog As New DataSet
Dim dsYears As New DataSet
Dim dsOrderTypes As New DataSet
Dim dsOrderColours As New DataSet
Dim dsOrders As New DataSet
Dim dsSupplies As New DataSet
Dim dtCatalog As New DataTable
Dim dtYears As New DataTable
Dim dtOrderTypes As New DataTable
Dim dtOrderColours As New DataTable
Dim dtOrders As New DataTable
Dim dtOrderColours As New DataTable
Dim dtSupplies As New DataTable
Dim daCatalog As New MySqlDataAdapter
Dim daYears As New MySqlDataAdapter
Dim daOrderTypes As New MySqlDataAdapter
Dim daOrderColours As New MySqlDataAdapter
Dim daOrders As New MySqlDataAdapter
Dim daSupplies As New MySqlDataAdapter

Private Sub Form1_Shown(sender As Object, e As EventArgs) Handles MyBase.Shown
    MysqlConn.ConnectionString =
    "server=localhost;Port=3306;database=mydatabase;userid=root;password=mypassword;persist security info=True"
    daOrders = New MySqlDataAdapter("SELECT * FROM Orders", MysqlConn)
    daOrders.MissingSchemaAction = MissingSchemaAction.AddWithKey
    Dim dsOrders As New DataSet
    dtOrders = New DataTable("Orders")
    daOrders.Fill(dtOrders)
    dsOrders.Tables.Add(dtOrders)
    Dim cbOrders As New MySqlCommandBuilder(daOrders)
    daSupplies = New MySqlDataAdapter("SELECT * FROM Supplies", MysqlConn)
    dtSupplies = New DataTable("Supplies")
    daSupplies.Fill(dtSupplies)
    dsOrders.Tables.Add(dtSupplies)
    cbOrders = New MySqlCommandBuilder(daSupplies)

    daCatalog = New MySqlDataAdapter("SELECT * FROM Catalog", MysqlConn)
    dtCatalog = New DataTable("Catalog")
    daCatalog.Fill(dtCatalog)
    dsOrders.Tables.Add(dtCatalog)
    cbOrders = New MySqlCommandBuilder(daCatalog)

    daYears = New MySqlDataAdapter("SELECT * FROM Years", MysqlConn)
    dtYears = New DataTable("Years")
    daYears.Fill(dtYears)
    dsOrders.Tables.Add(dtYears)
    cbOrders = New MySqlCommandBuilder(daYears)


    daOrderTypes = New MySqlDataAdapter("SELECT * FROM OrderTypes", MysqlConn)
    dtOrderTypes = New DataTable("OrderTypes")
    daOrderTypes.Fill(dtOrderTypes)
    dsOrders.Tables.Add(dtOrderTypes)
    cbOrders = New MySqlCommandBuilder(daOrderTypes)

    daOrderColours = New MySqlDataAdapter("SELECT * FROM OrderColours", MysqlConn)
    dtOrderColours = New DataTable("OrderColours")
    daOrderColours.Fill(dtOrderColours)
    dsOrders.Tables.Add(dtOrderColours)
    cbOrders = New MySqlCommandBuilder(daOrderColours)

    dtOrders.Columns("OrderID").AutoIncrement = True
    dtSupplies.Columns("SupplyID").AutoIncrement = True

    dtOrders.Columns(0).AutoIncrementSeed = dtSupplies.Rows.Cast(Of DataRow).Max(Function(dr As DataRow) CInt(dr.Item(0))) + 1
    dtSupplies.Columns(0).AutoIncrementStep = 1

    dtSupplies.Columns(0).AutoIncrementSeed = dtSupplies.Rows.Cast(Of DataRow).Max(Function(dr) CInt(dr.Item(0))) + 1
    dtSupplies.Columns(0).AutoIncrementStep = 1

    dsOrders.Relations.Add(New DataRelation("relationSupply", dsOrders.Tables("Supplies").Columns("SupplyID"), dsOrders.Tables("Orders").Columns("SupplyID_fkey")))

    SupplyBindingSource = New BindingSource(dsOrders, "Supplies")

    CboSupplyID_fkey.DisplayMember = "SupplyNumber"
    CboSupplyID_fkey.ValueMember = "SupplyID"
    CboSupplyID_fkey.DataSource = SupplyBindingSource

    OrderBindingSource = New BindingSource(SupplyBindingSource, "relationSupply")

    'bind the Supply's foreign key to the combobox's "SelectedValue" '
    Me.CboSupplyID_fkey.DataBindings.Add(New System.Windows.Forms.Binding("SelectedValue", Me.OrderBindingSource, "SupplyID_fkey", True))


    dtOrders.Columns("OrderID").AutoIncrement = True
    dtCatalog.Columns("CatalogCodeID").AutoIncrement = True

    dtOrders.Columns(0).AutoIncrementSeed = dtCatalog.Rows.Cast(Of DataRow).Max(Function(dr As DataRow) CInt(dr.Item(0))) + 1
    dtCatalog.Columns(0).AutoIncrementStep = 1

    dtCatalog.Columns(0).AutoIncrementSeed = dtCatalog.Rows.Cast(Of DataRow).Max(Function(dr) CInt(dr.Item(0))) + 1
    dtCatalog.Columns(0).AutoIncrementStep = 1

    dsOrders.Relations.Add(New DataRelation("relationCatalog", dsOrders.Tables("Catalog").Columns("CatalogCodeID"), dsOrders.Tables("Orders").Columns("CatalogCodeID_fk")))

    CatalogBindingSource = New BindingSource(dsOrders, "Catalog")

    CboCatalogCodeID_fk.DisplayMember = "CatalogDescription"
    CboCatalogCodeID_fk.ValueMember = "CatalogCodeID"
    CboCatalogCodeID_fk.DataSource = CatalogBindingSource

    OrderBindingSource = New BindingSource(CatalogBindingSource, "relationCatalog")

    'to clear previous binding and then add new binding '
    CboSupplyID_fkey.DataBindings.Clear()

    'bind the Catalog Guide's foreign key to the combobox's "SelectedValue" '
    Me.CboCatalogCodeID_fk.DataBindings.Add(New System.Windows.Forms.Binding("SelectedValue", Me.OrderBindingSource, "CatalogCodeID_fk", True))

    dtOrders.Columns("OrderID").AutoIncrement = True
    dtYears.Columns("YearID").AutoIncrement = True

    dtOrders.Columns(0).AutoIncrementSeed = dtYears.Rows.Cast(Of DataRow).Max(Function(dr As DataRow) CInt(dr.Item(0))) + 1
    dtYears.Columns(0).AutoIncrementStep = 1

    dtYears.Columns(0).AutoIncrementSeed = dtYears.Rows.Cast(Of DataRow).Max(Function(dr) CInt(dr.Item(0))) + 1
    dtYears.Columns(0).AutoIncrementStep = 1

    dsOrders.Relations.Add(New DataRelation("relationYears", dsOrders.Tables("Years").Columns("YearID"), dsOrders.Tables("Orders").Columns("YearID_fk")))

    YearBindingSource = New BindingSource(dsOrders, "Years")

    CboYearID_fk.DisplayMember = "YearNumber"
    CboYearID_fk.ValueMember = "YearID"
    CboYearID_fk.DataSource = YearBindingSource

    OrderBindingSource = New BindingSource(YearBindingSource, "relationYears")

    'to clear previous binding and then add new binding '
    CboCatalogCodeID_fk.DataBindings.Clear()

    'bind the Year's foreign key to the combobox's "SelectedValue" '
    Me.CboYearID_fk.DataBindings.Add(New System.Windows.Forms.Binding("SelectedValue", Me.OrderBindingSource, "YearID_fk", True))



    dtOrders.Columns("OrderID").AutoIncrement = True
    dtOrderTypes.Columns("OrderTypeID").AutoIncrement = True

    dtOrders.Columns(0).AutoIncrementSeed = dtOrderTypes.Rows.Cast(Of DataRow).Max(Function(dr As DataRow) CInt(dr.Item(0))) + 1
    dtOrderTypes.Columns(0).AutoIncrementStep = 1

    dtOrderTypes.Columns(0).AutoIncrementSeed = dtOrderTypes.Rows.Cast(Of DataRow).Max(Function(dr) CInt(dr.Item(0))) + 1
    dtOrderTypes.Columns(0).AutoIncrementStep = 1

    dsOrders.Relations.Add(New DataRelation("relationOrderTypes", dsOrders.Tables("OrderTypes").Columns("OrderTypeID"), dsOrders.Tables("Orders").Columns("OrderTypeID_fk")))

    OrderTypeBindingSource = New BindingSource(dsOrders, "OrderTypes")

    CboOrderTypeID_fk.DisplayMember = "OrderType"
    CboOrderTypeID_fk.ValueMember = "OrderTypeID"
    CboOrderTypeID_fk.DataSource = OrderTypeBindingSource

    OrderBindingSource = New BindingSource(OrderTypeBindingSource, "relationOrderTypes")

    'to clear previous binding and then add new binding '
    CboYearID_fk.DataBindings.Clear()

    'bind the Order Type's foreign key to the combobox's "SelectedValue" '
    Me.CboOrderTypeID_fk.DataBindings.Add(New System.Windows.Forms.Binding("SelectedValue", Me.OrderBindingSource, "OrderTypeID_fk", True))


    dtOrders.Columns("OrderID").AutoIncrement = True
    dtOrderColours.Columns("ColourID").AutoIncrement = True

    dtOrders.Columns(0).AutoIncrementSeed = dtOrderColours.Rows.Cast(Of DataRow).Max(Function(dr As DataRow) CInt(dr.Item(0))) + 1
    dtOrderColours.Columns(0).AutoIncrementStep = 1

    dtOrderColours.Columns(0).AutoIncrementSeed = dtOrderColours.Rows.Cast(Of DataRow).Max(Function(dr) CInt(dr.Item(0))) + 1
    dtOrderColours.Columns(0).AutoIncrementStep = 1

    dsOrders.Relations.Add(New DataRelation("relationColours", dsOrders.Tables("OrderColours").Columns("ColourID"), dsOrders.Tables("Orders").Columns("ColourID_fk")))

    OrderColourBindingSource = New BindingSource(dsOrders, "OrderColours")

    cboColourID_fk.DisplayMember = "Colour"
    cboColourID_fk.ValueMember = "ColourID"
    cboColourID_fk.DataSource = OrderColourBindingSource

    OrderBindingSource = New BindingSource(OrderColourBindingSource, "relationColours")

    'to clear previous binding and then add new binding '
    CboOrderTypeID_fk.DataBindings.Clear()

    'bind the Catalog Guide's foreign key to the combobox's "SelectedValue" '
    Me.cboColourID_fk.DataBindings.Add(New System.Windows.Forms.Binding("SelectedValue", Me.OrderBindingSource, "ColourID_fk", True))


    'Bind the DataTable to the UI via a BindingSource. '
    OrderBindingSource.DataSource = dtOrders
    Me.OrderBindingNavigator.BindingSource = Me.OrderBindingSource

    txtOrderID.DataBindings.Add("Text", Me.OrderBindingSource, "OrderID")
    txtOrderName.DataBindings.Add("Text", Me.OrderBindingSource, "OrderName")
End Sub
End Class

【问题讨论】：

我马上看到的一件事是您正在创建所有数据对象中的 2 个；一个在你用New 实例化的声明中，然后在你用New 再次实例化的Sub 过程中。
嗨，玛丽，感谢您的 cmets。你指的是哪两个对象？
Dim daSupplies As New MySqlDataAdapter 和 daSupplies = New MySqlDataAdapter("SELECT * FROM Supplies", MysqlConn) 似乎所有数据对象都会发生这种情况，而不仅仅是 2。我的意思是你正在创建 2。你在同一个对象上使用了两次 New 关键字。您在声明中创建一个，然后在分配中用另一个新的替换它。每次调用对象的构造函数。

标签： mysql vb.net visual-studio combobox

【解决方案1】：

感谢您的帮助。我能够通过使用这个 vb.net 代码来解决我的问题：-

        MysqlConn = New MySqlConnection()

    ' Define the SQL to grab data from table.
    CmdSQLSelectOrders = "SELECT * FROM Orders"

    'Connection String
    MysqlConn.ConnectionString =
      "server=localhost;Port=3306;database=mydatabase;userid=root;password=mypassword;persist security info=True"
    daOrders.MissingSchemaAction = MissingSchemaAction.AddWithKey
    ' Try, Catch, Finally
    Try
        MysqlConn.Open()

        MysqlCmd.Connection = MysqlConn
        MysqlCmd.CommandText = CmdSQLSelectOrders

        daOrders.SelectCommand = MysqlCmd
        daOrders.Fill(dtOrders)

        daSupplies = New MySqlDataAdapter("SELECT * FROM Supplies", MysqlConn)
        dtSupplies = New DataTable("Supplies")
        daSupplies.Fill(dtSupplies)
        dsOrders.Tables.Add(dtSupplies)

        daCatalog = New MySqlDataAdapter("SELECT * FROM Catalog", MysqlConn)
        dtCatalog = New DataTable("Catalog")
        daCatalog.Fill(dtCatalog)
        dsOrders.Tables.Add(dtCatalog)

        daYears = New MySqlDataAdapter("SELECT * FROM Years", MysqlConn)
        dtYears = New DataTable("Years")
        daYears.Fill(dtYears)
        dsOrders.Tables.Add(dtYears)

        daOrderTypes = New MySqlDataAdapter("SELECT * FROM OrderTypes", MysqlConn)
        dtOrderTypes = New DataTable("OrderTypes")
        daOrderTypes.Fill(dtOrderTypes)
        dsOrders.Tables.Add(dtOrderTypes)

        daOrderColours = New MySqlDataAdapter("SELECT * FROM OrderColours", MysqlConn)
        dtOrderColours = New DataTable("OrderColours")
        daOrderColours.Fill(dtOrderColours)
        dsOrders.Tables.Add(dtOrderColours)

        Me.CboSupplyID_fkey.DisplayMember = "SupplyNumber"
        Me.CboSupplyID_fkey.ValueMember = "SupplyID"
        Me.CboSupplyID_fkey.DataSource = SupplyBindingSource

        Me.CboCatalogID_fk.DisplayMember = "CatalogDescription"
        Me.CboCatalogID_fk.ValueMember = "CatalogID"
        Me.CboCatalogID_fk.DataSource = CatalogBindingSource

        Me.CboYearID_fk.DisplayMember = "Year"
        Me.CboYearID_fk.ValueMember = "YearID"
        Me.CboYearID_fk.DataSource = YearBindingSource


        Me.CboOrderTypeID_fk.DisplayMember = "OrderType"
        Me.CboOrderTypeID_fk.ValueMember = "OrderTypeID"
        Me.CboOrderTypeID_fk.DataSource = OrderTypeBindingSource

        Me.CboColourID_fk.DisplayMember = "Colour"
        Me.CboColourID_fk.ValueMember = "ColourID"
        Me.CboColourID_fk.DataSource = OrderColourBindingSource

        Me.OrderBindingSource.DataSource = ds.Tables("dtSupplies")
        Me.OrderBindingSource.DataSource = ds.Tables("dtCatalog")
        Me.OrderBindingSource.DataSource = ds.Tables("dtYears")
        Me.OrderBindingSource.DataSource = ds.Tables("dtOrderTypes")
        Me.OrderBindingSource.DataSource = ds.Tables("dtOrderColours")

        Me.OrderBindingNavigator.BindingSource = Me.OrderBindingSource

        Me.CboSupplyID_fk.DataBindings.Add("SelectedValue", Me.OrderBindingSource, "SupplyID_fk", True)
        Me.CboCatalogID_fk.DataBindings.Add("SelectedValue", Me.OrderBindingSource, "CatalogID_fk", True)
        Me.CboYearID_fk.DataBindings.Add("SelectedValue", Me.OrderBindingSource, "YearID_fk", True)
        Me.CboOrderTypeID_fk.DataBindings.Add("SelectedValue", Me.OrderBindingSource, "OrderTypeID_fk", True)
        Me.CboColourID_fk.DataBindings.Add("SelectedValue", Me.OrderBindingSource, "ColourID_fk", True)

    Catch myerror As MySqlException
        MessageBox.Show("Cannot connect to database: " & myerror.Message)
    Finally
        MysqlConn.Close()
        MysqlConn.Dispose()
    End Try

【讨论】：

用品

目录

年

颜色

订单