Question

我有一个使用一组三个组合框的应用程序。我已设法根据前一个下拉列表的选定值填充每个下拉列表唯一的问题是，由于数据来自数据库，来自第一个组合框的两个选定值可能在数据库中具有两个不同数量的项目。因此，每次调用第一个组合框的selectedIndex_changed nethod时，第二个组合框应填充此类数据

例如，如果第一个组合框的第一个项目在第二个组合框中有10个对应的项目，而第一个组合框的第二个项目在第二个组合框中有三个对应的项目，则在选择第一个项目后选择第二个项目将导致第二个组合框显示三个项目，七个空白项目落后于三个项目。

我想要的是当第一个组合框中的第二个项目在数据库中有三个项目时，第二个组合框完全加载了三个项目

这是一个例子

Private Sub cboAccountGroup_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As   System.EventArgs) Handles cboAccountGroup.SelectedIndexChanged
    If mblnAccountGroupFirstLoad = True Then
        Exit Sub
    End If
    Dim index As String
    index = cboAccountGroup.SelectedValue
    'Call clearDataEntries()
    Dim psql As String
    psql = "Select Account_Type_ID,Description from Tbl_Account_Type Where Account_Group_id=" & index
    Call setDropDowns(cboAccountType, psql)
    mblnAccountTypeFirstLoad = False

End Sub

setDropDowns定义如下

 Public Sub setDropDowns(ByRef combo As ComboBox, ByVal sql As String)


    Try
        Dim adaptor As New SqlDataAdapter(sql, mcon)
        Dim dataset As New DataTable()
        mcon.Open()
        adaptor.Fill(DataSet)
        mcon.Close()

        combo.DataSource = DataSet
        combo.DisplayMember = DataSet.Columns(1).ColumnName
        combo.ValueMember = DataSet.Columns(0).ColumnName


    Catch ex As Exception
    Finally
        'mcon.Close()

    End Try

End Sub

请协助。

Answer 1

我会稍微改变代码看起来更像这样：

'Build functions that return data, and keep them separate from code that updates your UI
Public Function GetAccountTypesByAccountID(ByVal AccountGroupID As Integer) As DataTable

    Dim sql As String = "SELECT Account_Type_ID,Description FROM Tbl_Account_Type Where Account_Group_id= @AccountGroupID"
    Dim result As New DataTable()

    'Create a new connection each time. Really! Thanks to connection pooling, this is the way to go
    Using mcon As New SqlConnection(GetConnectionString()), _
          cmd As New SqlCommand(sql, mcon)

        'USE PARAMETERIZED QUERIES!!
        cmd.Parameters.Add("@AccountGroupID", SqlDbTypes.Int).Value = AccountGroupID

        'The Using block will make sure the connection is closed, even if an exception is thrown
        mcon.Open()
        Using rdr As SqlDataReader = cmd.ExecuteReader()
            result.Load(rdr)
        End Using
    End Using
    Return result
End Function


Private Sub cboAccountGroup_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As   System.EventArgs) Handles cboAccountGroup.SelectedIndexChanged
    If mblnAccountGroupFirstLoad Then Exit Sub
    mblnAccountTypeFirstLoad = False

    ' clearDataEntries()

    Dim AccountTypes As DataTable = GetAccountTypesByAccountID(Integer.Parse(cboAccountGroup.SelectedValue))

    cboAccountType.DisplayMember = AccountTypes.Columns(1).ColumnName
    cboAccountType.ValueMember   = AccountTypes.Columns(0).ColumnName
    cboAccountType.DataSource = AccountTypes 'Set datasoure LAST

End Sub

Visual Basic 2008中的动态下拉菜单

1 个答案: