I'll be honest here and say that I think Sonar's controller lanes are horrible. They're not user friendly at all and I hate using them, which is why I try to avoid them as much as possible. I believe Sonar's implementation of automation and controllers needs a huge revamp because it's a confusing mess. 
 
Anyway, so onto my question. How do you delete an entire controller lane's worth of data quickly and easily? I cannot find any mention of it in the manual. I had to create some NRPN controller lanes to automate the parameters in a Reaktor effect because the parameters were not showing up in the automation lanes (that's a whole other frustrating story). I've now decided that I want to delete all of this controller data and start again. Only there seems to be no obvious way to just delete the whole lane of data. 
 
If you click the '-' icon, it just hides the lane without removing the data. Right clicking in the controller lanes doesn't bring up a menu like it does in automation lanes (from which I'd simply select "delete envelope"). If I CTRL-A to select everything in the lane, it selects all of the MIDI data in the track, meaning I'd lose everything (clips, other lanes, everything) if I hit delete. So the only method I've found so far is to zoom out until the whole project is visible on the screen, use the select tool to lasso all of the controller data, then hit delete. But it just seems like there should be a quicker, easier, one click method which requires no zooming or lassoing. Does anyone have any ideas? Right now it feels like controller lanes were slapped onto the program 20 years ago and never updated. 

To delete all controller events in a Sonar project quickly, this is how I would do it.

1) Select all tracks that contain the controllers you wish to delete.
2) Open menu item EDIT|SELECT|BY FILTER
3) Click "none"
4) Put a tick next to "control" (and optionally RPN and NRPN and press "OK").
5) Hit "delete"

Note: in step 4 you can narrow the selection down even further if desired - for instance you might want to select just volume events (Controller 7).

I hope this helps.

BTW: I agree with you that the controller lanes in Sonar needs a massive overhaul

Tbh promidi that sounds even more fiddly than lassoing everything with the select tool! 

I tend to use Select By Filter for this as well, but if you want to do it it in the PRV, you can zoom out and sweep the lane with the Erase tool.

Looks like I should put in a feature request. It shouldn't be any harder or less convenient to edit a controller lane than an automation lane. 

Ooops controller lanes Somehow I missed that, sounds like a midi Issue instead of take lanes which I ass,umed DOH!!!
 
 
Honestly I hear ya!!!!!
I also hate Take lanes especially when you don't even realise you have started a second take and you go to replay and there are five take lanes.
I do 1 track record, then press Control Z if its not any good and that way I never get to the take lane fiasco.
At one point I liked it, Maybe Sonar 8.5 then they changed it and I have hated it ever since.
 

I usually go to the Event List View and hold my finger down on the delete key till they're all gone.  Primitive, but it seems to work.
 
I am totally with ya on revamping this feature.  Even my circa 1987 Yamaha QX-5 hardware sequencer could delete events VERY quickly and easily.  sheesh.

Use the erase tool and just sweep through the controllers you want deleted.
 
It's not a one click solution but it's pretty quick