为什么要将Excel数据导入到datagridview需要这么长时间？

Question

我想将一个大文件从excel文件加载到vb.net datagridview，但是当我运行该程序时，要花很长时间将所有数据加载到datagridview中，这是我导入excel文件的一些代码。

Public Sub sheetArray2(ByVal filePath As TextBox, ByVal dtg As DataGridView)
        conn = New OleDb.OleDbConnection("Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" & filePath.Text & ";Extended Properties=Excel 12.0;")
        conn.Open()
        dt = New DataTable
        dt = conn.GetOleDbSchemaTable(OleDbSchemaGuid.Tables, Nothing)
        listSheet = New List(Of String)
        For Each drSheet In dt.Rows
            listSheet.Add(drSheet("TABLE_NAME").ToString)
        Next
        dt1 = New DataTable
        For i As Integer = 0 To listSheet.Count - 1
            da = New OleDb.OleDbDataAdapter("select *from [" & listSheet.Item(i) & "]", conn)
            da.Fill(dt1)
            Dim ar(dt1.Columns.Count, dt1.Rows.Count)
            For x As Integer = 0 To dt1.Rows.Count - 1
                dtg.DataSource = dt1
                For y As Integer = 0 To dt1.Columns.Count - 1
                    ar.SetValue(dt1.Rows(x).Item(y), y, x)
                    dtg.Item(y, x).Value = ar(y, x)
                Next
            Next
        Next
        conn.Close()

    End Sub