我尝试过此代码，该文件打开但为空。我的Pdf数据已保存为Long二进制数据，可以访问。

Private Sub Button2_Click(sender As Object,e As EventArgs) Handles Button2.Click
    Dim cmd As New OleDbCommand("SELECT Pdf FROM tblBinary WHERE Identity = 'n'",cn)
    Dim dt1 As New DataTable

    'Dim fileData As Byte() = DirectCast(cmd.ExecuteScalar(),Byte())

    Using reader As OleDbdataReader = cmd.ExecuteReader()
        While reader.Read()
            Dim fileData As Byte() = DirectCast(reader("Pdf"),Byte())

            Using fs As New FileStream("C:\Users\nelsn\Desktop\Testing1.doc",FileMode.Create,Fileaccess.Write)
                fs.Write(fileData,fileData.Length)
                fs.Flush()
                fs.Close()
            End Using
            System.Diagnostics.Process.Start("C:\Users\nelsn\Desktop\Testing1.doc")
        End While
    End Using
End Sub