modelsim question. help me.

smalldog

Hi, All,

I meet a question when I use modelsim.
The question is:
After I finished a simulation, I can see signals in the dataflow and waveform windows. Then I save a .wlf file.
Then I closed the modelsim tools. Then I reopen the modelsim again. Then I only open the .wfl file without running others. I can only see signals in waveform windows. I can't see ang signals in dataflow windows yet.And I drag signal from other windows to dataflow windows. It is still nothing. Before I close modelsim, I can see the signals in dataflow windows. But after I close modelsim and reopne modelsim, I can't see anything in dataflow windows.
The tools shows me "Error: Active logfile is not in simulation mode"

Could you give me some suggestion?
Thanks a lot.