Xamarin iOS Try Catch blocks crash app instead of catching

Question

I have been debugging an issue on my Xamarin iOS application. I noticed that instead of hitting a catch on a try catch block. the App just shuts down. I'm not sure when this started happening as this is the first time I have noticed this.

But now I've put the following code in multiple spots in my application. No matter what happens, when this code is hit a null reference exception crashes the app and does not get caught by the catch. This is true both when using a general catch or a specific crash (NullReferenceException).

string testers = "";
CustomObject test = null;
try
{
testers = test.property;
}
catch (Exception e)
{
testers = "fail";
}

When debugging this the attempt to access the property fails and the app immediately shuts down. The catch statement is not triggered. I have put this in multiple places in my app. I have no idea why it isn't being caught. There are multiple points where I use try catches to prevent failures in the app. It would be appreciated if someone could explain this, or give me some ideas on how to prevent this.

I should note, this is Xamarin iOS code not Xamarin.Forms.

Thanks,

Update
This code does function correctly (not crash) when I place it within my AppDelegate.cs FinishedLaunching method. I'm not sure why but maybe there is a way to get it working in other parts of the app (e.g., viewcontrollers)

Update 2
I've noticed if I replace the code attempting to access a property of null object with "throw new NullReferenceException();" The catch will trigger. Of coarse this isn't very helpful to me.

Answer 1

Hello,

Welcome to Microsoft Q&A!

Could you provide more information ?

What's the version of Xamarin.iOS you're using ?
What's the simulator/real device did you test on ?

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Since I test with Xamarin.iOS 14.14.2.5 and test on simulator iPhone 12 , everything works fine .

No matter I place the code in AppDelegate or ViewController , the exception was caught as expected .

Could you try replace Exception with NullReferenceException ?

Or just use testers = test?.property; instead of placing it into try catch .

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