一种快速且有点脏的方法是在reader中添加count和count到3。。这不是任务的最佳解决方案，但它会起作用：）

Using conn As New MySqlConnection("server=localhost;user=root;password=;database=dbrentalsystem")
    conn.Open()
    Dim commandReader As New MySqlCommand("select * from tbl_unit", conn)
    Dim reader As MySqlDataReader = commandReader.ExecuteReader
    Dim i as integer = 1
    While reader.Read
        if i = 3 then
           If reader.IsDBNull(2) Then
               lblUnit1.Text = "Vacant"
           Else
               lblUnit1.Text = "Occupied"
           End If
        end if
    i += 1
    End While
    commandReader.Dispose()
    reader.Close()
    con.Close()
End Using