Hi Chris,
The Measurement Studio .NET DigitalWaveformGraph does not support appending data. Each time you call PlotWaveform the old data that was previously plotted is gone and the new data in the DigitalWaveform is plotted. Now, I can't think of any reason why we can't support this feature so I would suggest that you submit a product suggestion indicating you wish to see this feature.
Now, because of the current design, you will need to keep track of the data previously written and append the waveforms yourself and then plot the updated waveform. The two ways of doing this I can currently think of are
1) Use the DigitalWaveform.CopyStates static method. The second overload allows you to insert the data at a particular index so you might want to look at that.
2) You could always read in the data as a array and then conver that array to a DigitalWaveform using the DataConverter class. You would keep adding to this array and then converting it over to a DigitalWaveform for plotting purposes.
Best Regards,
Jonathan N.
National Instruments
