How do I remove a Task Channel and then recreate it?

[JoyS]

I'm writing an application in C# on a Windows XP platform using version NI-DAQmx version 7.4. I need to be able to create a task, add channels to it, then delete those channels and add new channels.

For example, I create a channel using the CreateVoltageChannel function, then I call the Dispose function which I thought would remove it.  But if I make a subsequent call to the CreateVoltageChannel function, I get an error stating that I'm trying to read or write protected memory.  I've been trying to find a way to explicitly remove channels from a Task, but the documentation suggests that the Dispose function does this.  If so, why can't I create a new channel?

Thanks,

Joy

[TheWoost]

Hi Joy,

Unfortunately there is not way to remove channels from a task currently.  When you get a reference to a channel it actually returns a copy of the channel rather than a reference to the channel inside the task.  This means the dispose function does not remove the channel from the task.

If you need to have different channels in a task, it is recommended to clear the current task to free up the reserved resources and then create a new task with the new channels.

Regards,
Andrew W
National Instruments

[Tyzack]

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TheWoost wrote:

If you need to have different channels in a task, it is recommended to clear the current task to free up the reserved resources and then create a new task with the new channels.

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Does this hold true for triggers on a channel? I have one task, with a finite set of channels, but I want to dynamically change how data is collected of them. Sometimes I want to get one point from each channel (single read, no trigger) other times I want to use a reference tirgger to read N samples from all the channel asyncronously.

[Chris_D]

Tyzack,

After stopping a task you are able to make modifications to the task. This means you should be able to modify the trigger options. Please continue this discussion at your other thread here.