"Conversion from string "“键入 'Boolean' 无效。”

Question

如果 "Conversion from string "" 键入 'Boolean' 无效，我会遇到问题。"

If xlstxtbox1.Text = "" & xlstxtbox2.Text = "" & xlstxtbox3.Text = "" Then
                    cmdselcet = New OleDbCommand("select * from [sheet1$]",cn)
                    '2
                ElseIf xlstxtbox1.Text <> "" & xlstxtbox2.Text = "" & xlstxtbox3.Text = "" Then
                    cmdselcet = New OleDbCommand("select " + xlstxtbox1.Text + "from [sheet1$] ", cn)
                    '3
                ElseIf xlstxtbox1.Text = "" & xlstxtbox2.Text <> "" & xlstxtbox3.Text = "" Then
                    cmdselcet = New OleDbCommand("select * from [" + xlstxtbox2.Text + "$] ", cn)
                    '4
                ElseIf xlstxtbox1.Text = "" & xlstxtbox2.Text = "" & xlstxtbox3.Text <> "" Then
                    cmdselcet = New OleDbCommand("select * from [sheet1$] " + xlstxtbox3.Text, cn)
                    '5
                ElseIf xlstxtbox1.Text <> "" & xlstxtbox2.Text <> "" & xlstxtbox3.Text = "" Then
                    cmdselcet = New OleDbCommand("select " + xlstxtbox1.Text + "from [" + xlstxtbox2.Text + "$] ", cn)
                    '6
                ElseIf xlstxtbox1.Text = "" & xlstxtbox2.Text <> "" & xlstxtbox3.Text <> "" Then
                    cmdselcet = New OleDbCommand("select * from [" + xlstxtbox2.Text + "$] " + xlstxtbox3.Text, cn)
                    '7
                ElseIf xlstxtbox1.Text <> "" & xlstxtbox2.Text = "" & xlstxtbox3.Text <> "" Then
                    cmdselcet = New OleDbCommand("select " + xlstxtbox1.Text + " from [sheet1$] " + xlstxtbox3.Text, cn)
                    '8
                ElseIf xlstxtbox1.Text <> "" & xlstxtbox2.Text <> "" & xlstxtbox3.Text <> "" Then
                    cmdselcet = New OleDbCommand("select " + xlstxtbox1.Text + " from [" + xlstxtbox2.Text + "$] " + xlstxtbox3.Text, cn)
                End If

Answer 1

这就是答案。

Private Sub xls_opn(sender As Object, e As EventArgs) 句柄 openxls.Click

    Dim cmdselcet = New OleDbCommand

    Dim adapter As New OleDbDataAdapter

    Using cn As New OleDbConnection(constr)

        Try

            cn.Open()

            '1 üres,üres,üres
            If xlstxtbox1.Text.Length = 0 & xlstxtbox2.Text.Length = 0 & xlstxtbox3.Text.Length = 0 Then
                cmdselcet = New OleDbCommand("select * from [sheet1$]", cn)

                '2 nem,üres,üres
            ElseIf xlstxtbox1.Text.Length <> 0 & xlstxtbox2.Text.Length = 0 & xlstxtbox3.Text.Length = 0 Then
                cmdselcet = New OleDbCommand("select " + xlstxtbox1.Text + " from [sheet1$] ", cn)

                '3 üres,nem,üres
            ElseIf xlstxtbox1.Text.Length = 0 & xlstxtbox2.Text.Length <> 0 & xlstxtbox3.Text.Length = 0 Then
                cmdselcet = New OleDbCommand("select * from [" + xlstxtbox2.Text + "$] ", cn)

                '4 üres,üres,nem
            ElseIf xlstxtbox1.Text.Length = 0 & xlstxtbox2.Text.Length = 0 & xlstxtbox3.Text.Length <> 0 Then
                cmdselcet = New OleDbCommand("select * from [sheet1$] " + xlstxtbox3.Text, cn)

                '5 nem,nem,üres
            ElseIf xlstxtbox1.Text.Length <> 0 & xlstxtbox2.Text.Length <> 0 & xlstxtbox3.Text.Length = 0 Then
                cmdselcet = New OleDbCommand("select " + xlstxtbox1.Text + " from [" + xlstxtbox2.Text + "$] ", cn)

                '6 üres,nem,nem
            ElseIf xlstxtbox1.Text.Length = 0 & xlstxtbox2.Text.Length <> 0 & xlstxtbox3.Text.Length <> 0 Then
                cmdselcet = New OleDbCommand("select * from [" + xlstxtbox2.Text + "$] " + xlstxtbox3.Text, cn)

                '7 nem,üres,nem
            ElseIf xlstxtbox1.Text.Length <> 0 & xlstxtbox2.Text.Length = 0 & xlstxtbox3.Text.Length <> 0 Then
                cmdselcet = New OleDbCommand("select " + xlstxtbox1.Text + " from [sheet1$] " + xlstxtbox3.Text, cn)

                '8 nem,nem,nem
            ElseIf xlstxtbox1.Text.Length <> 0 & xlstxtbox2.Text.Length <> 0 & xlstxtbox3.Text.Length <> 0 Then
                cmdselcet = New OleDbCommand("select " + xlstxtbox1.Text + " from [" + xlstxtbox2.Text + "$] " + xlstxtbox3.Text, cn)
            End If

            adapter.SelectCommand = cmdselcet
            Dim ds As DataSet
            ds = New DataSet

            'Megjelenítés
            adapter.Fill(ds)
            DataGridView1.DataSource = ds.Tables(0)
            DataGridView1.Visible = True
            MsgBox("XLS/XLSX import kész!")

        Catch ex As Exception

            DataGridView1.Visible = False
            MsgBox(ex.Message)

        End Try

    End Using

End Sub

"Conversion from string "“键入 'Boolean' 无效。”

"Conversion from string "" to type 'Boolean' is not valid."

vba

type-conversion