Access Token Expired

I want to use Microsoft Translator to detect text language.
As in this page http://msdn.microsoft.com/en-us/library/hh454950.aspx#csharpexample, it explains that access token is valid for 10 minutes. And it has a sample C sharp code to generate a new access token after exceeding the time limit.

I simply revise this sample code to input data file, and the console window also shows that I have successfully renewed token. Yet error message still abort the program:"The incoming token has expired. Get a new access token from Authorization Server. message id=3811.V2_Rest.Detect.2C788FBE."

Could anyone solve this problem?