datagridview不会显示来自mysql的pdf文件，它在存放pdf的表上有红色的x标记。我希望文件名显示在datagridview上。我真的需要帮助。多谢了。我正在使用vb.net和workbench。

Private Sub Admin_Handouts_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    Try
        MysqlConn = New MySqlConnection
        MysqlConn.ConnectionString = "server=; userid=; password=; database=cai"
        MysqlConn.Open()
        sql = "SELECT Code FROM cai.subjects"
        command = New MySqlCommand(sql, MysqlConn)
        da = New MySqlDataAdapter
        dt = New DataTable
        da.SelectCommand = command
        da.Fill(dt)
        dgvfiles.DataSource = dt
    Catch ex As MySqlException
        MsgBox(ex.Message)
    Finally
        MysqlConn.Close()
        da.Dispose()
    End Try
End Sub