Excel和OpenFileDialog_openfiledialog限制excle

Imports Microsoft.Office.Interop
'COM Microsoft Excel x.0 Object Library
 
Public Class Form1
    Dim exApp As New Excel.Application
    Dim wb As Excel.Workbook
    Dim ws As Excel.Worksheet
 
    Dim openFileDiag As New OpenFileDialog()
    Dim excelPath As String
 
    Dim content(,) As String
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        openFileDiag.FileName = ""
        If openFileDiag.ShowDialog() = System.Windows.Forms.DialogResult.OK Then
            excelPath = openFileDiag.FileName
            'Debug.Print(excelPath)
        End If
    End Sub
 
    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        exApp.Visible = False  '不显示excel 程序
        wb = exApp.Workbooks.Open(excelPath)
        ws = wb.Sheets(1)
 
        ws.Cells(1, 1).value = "AAA"
        'Debug.Print(ws.Cells(8, 1).value)
        'Debug.Print(ws.UsedRange.Rows.Count)
 
        ReDim content(ws.UsedRange.Rows.Count, ws.UsedRange.Columns.Count)
        For i = 1 To ws.UsedRange.Rows.Count
            For j = 1 To ws.UsedRange.Columns.Count
                content(i, j) = ws.Cells(i, j).value
                Debug.Print(content(i, j))
            Next
        Next
 
        wb.Save()
        wb.Close()
        exApp.Quit()
 
    End Sub
End Class

exsheet:=excelapp.workbooks[1].worksheets[sheetname]; 

exBook = exApp.Workbooks.Open(appPath)

        exSheet = exBook.Sheets.Item(indexSheet)