TDMS Properties-I have a problem to set the TDMS properties (like description) with Chinese words

I tried to add description to my tdms file with the following step:

    tdmsfile.Description="some Chinese words";

or

    tdmsChannel.Description="some Chinese words";

or

    tdmsChannelGroup.Description="some Chinese words";

but only one or two words would be added, other Chinese words are lost.

I have tried very long English sentences and it works fine.