如何在vb.net中将ComboBox从绑定列表刷新到绑定源

Question

我尝试在 VB.NET 中将 ComboBox 从 BindingList 刷新到 BindingSource，但没有成功。

我的代码有问题吗？

是否可以通过BindingSource或BindingList或其他方法重置。

对于 Form2 我不想使用 ShowDialog 因为我不想关闭 Form2

所以我的帖子是重置或刷新组合框中的数据源

从提供的推荐链接发送数据，但如果我再次从组合框中进行下拉，数据肯定不会出现。

谢谢

Form1 中的代码

 Public Class Form1
     Private CatProdService As New CatProdService()
     Private bindingSource1 As BindingSource = Nothing
 
     Private Sub BindcomboboxCatProd()
         If ComboBox1.DataSource IsNot Nothing Then Return
             Cursor.Current = Cursors.WaitCursor
             ComboBox1.DisplayMember = "CatProd"
             ComboBox1.ValueMember = "CatProd"
 
             bindingSource1 = New BindingSource With {.DataSource = New BindingList(Of CatProd)(CType(CatProdService.GetByCatProd(), IList(Of CatProd)))}
             ComboBox1.DataSource = bindingSource1
             Cursor.Current = Cursors.Default
     End Sub

     Private Sub ComboBox1_DropDown(sender As Object, e As EventArgs) Handles ComboBox1.DropDown
         BindcomboboxCatProd()
     End Sub

     Private Sub ComboBox1_KeyDown(sender As Object, e As KeyEventArgs) Handles ComboBox1.KeyDown
         BindcomboboxCatProd()
     End Sub

     Private Sub BtnShowForm2_Click(sender As Object, e As EventArgs) Handles BtnShowForm2.Click
         Form2.Show()
         End Using
     End Sub
End Class

Public Class CatProd
    Public Property ID() As Integer
     Public Property CatProd() As String
     Public Property DesCatProd() As String
End Class

Public Class CatProdService
    Public Function GetOledbConnectionString() As String
        Return "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=|DataDirectory|\sample.accdb;Persist Security Info=False;"
    End Function

    Private ReadOnly _conn As OleDbConnection
    Private _connectionString As String = GetOledbConnectionString()

    Public Sub New()
        _conn = New OleDbConnection(_connectionString)
    End Sub

    Public Function GetByCatProd() As IEnumerable(Of CatProd)
        Dim sql = $"SELECT CatProd FROM CatProd"

        Using _conn = New OleDbConnection(GetOledbConnectionString())
            Return _conn.Query(Of CatProd)(sql).ToList()
        End Using
    End Function

    Public Function SearchHelper() As IEnumerable(Of CatProd)
        Dim sql = "SELECT * FROM CatProd"

        Using _conn = New OleDbConnection(GetOledbConnectionString())
            Return _conn.Query(Of CatProd)(sql).ToList()
        End Using
    End Function

    Public Sub InsertCatProd(ByVal Obj As CatProd)
        Dim sql = $"INSERT INTO `CatProd` (`CatProd`,`DesCatProd`) VALUES ('{Obj.CatProd}','{Obj.DesCatProd}');"
 
        Using _conn = New OleDbConnection(GetOledbConnectionString())
            _conn.Execute(sql)
        End Using
    End Sub
End Class

Form2 中的代码

Public Class Form2
    Dim CatProdService As New CatProdService()
    Private bindingSource1 As BindingSource = Nothing

    Private Sub Form2_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        LoadData1()
    End Sub

    Private Sub LoadData1()
        Dim Stock = CatProdService.SearchHelper()
        bindingSource1 = New BindingSource With {.DataSource = New BindingList(Of CatProd)(CType(CatProdService.SearchHelper(), IList(Of CatProd)))}
        DataGridView1.DataSource = bindingSource1
    End Sub

    Private Sub BtnSave_Click(sender As Object, e As EventArgs) Handles BtnSave.Click
        Try
            'insert new record
            CatProdService.InsertCatProd(New CatProd() With {
        .CatProd = txtCatProd.Text,
        .DesCatProd = txtDesCatProd.Text
    })
            MessageBox.Show("Successfull")
            LoadData1()
        Catch ex As Exception
            MessageBox.Show(ex.Message, "MYAPP", MessageBoxButtons.OK, MessageBoxIcon.Exclamation)
        End Try
    End Sub
End Class

gif 文件中代码的结果

Answer 1

注释掉下面的代码后问题解决了

 Private Sub BindcomboboxCatProd()
         'If ComboBox1.DataSource IsNot Nothing Then Return
             Cursor.Current = Cursors.WaitCursor
             ComboBox1.DisplayMember = "CatProd"
             ComboBox1.ValueMember = "CatProd"
 
             bindingSource1 = New BindingSource With {.DataSource = New BindingList(Of CatProd)(CType(CatProdService.GetByCatProd(), IList(Of CatProd)))}
             ComboBox1.DataSource = bindingSource1
             Cursor.Current = Cursors.Default
     End Sub

     Private Sub ComboBox1_DropDown(sender As Object, e As EventArgs) Handles ComboBox1.DropDown
If ComboBox1.DataSource IsNot Nothing Then Return
         BindcomboboxCatProd()
     End Sub

     Private Sub ComboBox1_KeyDown(sender As Object, e As KeyEventArgs) Handles ComboBox1.KeyDown
If ComboBox1.DataSource IsNot Nothing Then Return
         BindcomboboxCatProd()
     End Sub

```