Question

-在我使用hide（）和show（）在表单之间切换之后，我创建了2种表单。

-在第二种形式中，我创建数据表（绑定到数据网格）和主键以供数据表使用find（）。

-按第二个表格的[BACK]按钮返回第一个表格（使用hide（）和show（）函数），然后再次使用第二个表格应用程序。运行时错误显示此[System.Data.Missing.PrimaryKeyException：表没有主键]

第一表格

Public Class MainMenu

    Public MainForm As MainMenu
    Public AssetCheckForm As AssetCheck

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

        AssetCheckForm.Show()
        MainForm.Hide()

    End Sub

    Public Sub MainMenu_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        MainForm = New MainMenu()
        AssetCheckForm = New AssetCheck()
    End Sub End Class

第二张表格

Dim dtAsset As New DataTable("AssetTable")

Public Sub readData()
        If readStatus = 0 Then
            Try
                Dim splits As String()
                Using sr As StreamReader = New StreamReader(inputcsvname)
                    'read the first line for the table columns
                    splits = sr.ReadLine.Split(","c)
                    For i As Integer = 0 To UBound(splits)
                        dtAsset.Columns.Add(splits(i))
                    Next
                    'read the rest of the lines to add rows
                    Do While Not sr.EndOfStream
                        splits = sr.ReadLine.Split(","c)
                        dtAsset.Rows.Add(splits)
                    Loop
                End Using
            Catch ex As Exception
            Finally

            End Try

            dtAsset_display = dtAsset.Copy()
            totalcount.Text = getRowsCount(dtAsset_display)

            dtAsset.Columns("AsstCode").Unique = True
            dtAsset.PrimaryKey = New DataColumn() {dtAsset.Columns("AsstCode")}

            'bind display part to DataGrid
            DataGrid1.DataSource = dtAsset

Private Sub BackButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ButtonF4.Click
    clearData()
    MainMenu.MainForm.Show()
    MainMenu.AssetCheckForm.Hide()

End Sub

我想我错过了有关VB.net WinForm概念的信息。有人知道这个错误是什么意思吗？

Answer 1

您正在MainForm = New MainMenu()中呼叫MainForm的事实，这意味着您现在拥有MainForm的两个实例。

因此，当您致电MainMenu.MainForm.Show()时，您将显示新实例，而不是现有实例。

您需要对此进行更改，以便将对现有MainForm的引用存储在AssetCheckForm表单中。

类似这样的东西：

Public Class MainMenu

    Private AssetCheckForm As AssetCheckForm

    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        Me.AssetCheckForm = New AssetCheckForm
        Me.AssetCheckForm.MainMenu = Me
        Me.Hide()
        Me.AssetCheckForm.Show()
    End Sub

End Class

Public Class AssetCheckForm

    Friend MainMenu As MainMenu

    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        Me.MainMenu.Show()
        Me.Close()
    End Sub

End Class

VB.net WindowsForm更改然后[System.Data.MissingPrimaryKeyException]

1 个答案: