Bug 47926 - Programatically adding a UIPickerView causes MonotouchException
Summary: Programatically adding a UIPickerView causes MonotouchException
Alias: None
Product: iOS
Classification: Xamarin
Component: Xamarin.iOS.dll ()
Version: XI 10.4 (C9)
Hardware: Macintosh Mac OS
: --- normal
Target Milestone: Untriaged
Assignee: Bugzilla
Depends on:
Reported: 2016-11-25 01:22 UTC by Felix Collins
Modified: 2016-11-25 12:18 UTC (History)
2 users (show)

Is this bug a regression?: Yes
Last known good build: Not sure...

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Description Felix Collins 2016-11-25 01:22:11 UTC
2016-11-25 14:06:53.196 testuipickerview[8364:1721535] -[UIPickerViewModel numberOfComponentsInPickerView:]: unrecognized selector sent to instance 0x17eadb80
2016-11-25 14:06:53.200 testuipickerview[8364:1721535] Xamarin.iOS: Received unhandled ObjectiveC exception: NSInvalidArgumentException -[UIPickerViewModel numberOfComponentsInPickerView:]: unrecognized selector sent to instance 0x17eadb80

Steps to reproduce:
1. Create a single page ios application in Xamarin Studio.
2. Add these three lines to the ViewDidLoad method of the ViewController.cs
  			var view = new UIPickerView();
			view.Model = new UIPickerViewModel();
3. Run on ios 9.1 device (I'm running on iPad).
Comment 1 Vincent Dondain [MSFT] 2016-11-25 12:18:44 UTC

You have to give UIPickerView a data source otherwise iOS does not know how to populate it.

The solution here is to implement IUIPickerViewDataSource, Xamarin Studio should underline it in red to help you add the required methods "GetComponentCount" and "GetRowsInComponent" (press option + space on the interface), you'll then have to return some values of your choice and finally add "view.DataSource = this;"

So with the default SingleView App template you'd get a ViewController.cs like this: https://gist.github.com/VincentDondain/b2e4803d1402451300fdcd2fb8768478