Determine if an iOS device supports TouchID without setting passcode

The correct way to detect if TouchID is available:

BOOL hasTouchID = NO;
// if the LAContext class is available
if ([LAContext class]) {
    LAContext *context = [LAContext new];
    NSError *error = nil;
    hasTouchId = [context canEvaluatePolicy:LAPolicyDeviceOwnerAuthenticationWithBiometrics error:&error];
}

Sorry it is in Objective-C, you might have to translate it to C#.

You should refrain from checking the system version and just check whether or not the class or methods are available.

I know this is a question from last year, but this solution does not make what you need? (Swift code)

if #available(iOS 8.0, *) {
    var error: NSError?
    let hasTouchID = LAContext().canEvaluatePolicy(LAPolicy.DeviceOwnerAuthenticationWithBiometrics, error: &error)

    //Show the touch id option if the device has touch id hardware feature (even if the passcode is not set or touch id is not enrolled)
    if(hasTouchID || (error?.code != LAError.TouchIDNotAvailable.rawValue)) {
        touchIDContentView.hidden = false
    } 
}

Then, when the user presses the button to log in with touch id:

@IBAction func loginWithTouchId() {
    let context = LAContext()

    var error: NSError?
    let reasonString = "Log in with Touch ID"

    if (context.canEvaluatePolicy(LAPolicy.DeviceOwnerAuthenticationWithBiometrics, error: &error)) {
        [context.evaluatePolicy(LAPolicy.DeviceOwnerAuthenticationWithBiometrics, localizedReason: reasonString, reply: { (success: Bool, evalPolicyError: NSError?) -> Void in
            //Has touch id. Treat the success boolean
        })]
    } else { 
        //Then, if the user has touch id but is not enrolled or the passcode is not set, show a alert message
        switch error!.code{

        case LAError.TouchIDNotEnrolled.rawValue:
            //Show alert message to inform that touch id is not enrolled
            break

        case LAError.PasscodeNotSet.rawValue:
            //Show alert message to inform that passcode is not set
            break

        default:
            // The LAError.TouchIDNotAvailable case.
            // Will not catch here, because if not available, the option will not visible
        }
    }
}

Hope it helps!

In conclusion of the discussion below, for the time being it is not possible to determine whether a device actually supports TouchID or not when the user hasn't set up passcode on their device.

I have reported this TouchID flaw on the Apple bug reporter. Those who want to follow the issue can see it on Open Radar here: http://www.openradar.me/20342024

Thanks @rckoenes for the input :)

EDIT

Turns out that someone has reported a similar issue already (#18364575). Here is Apple's reply regarding the issue:

"Engineering has determined that this issue behaves as intended based on the following information:

If passcode is not set, you will not be able to detect Touch ID presence. Once the passcode is set, canEvaluatePolicy will eventually return LAErrorTouchIDNotAvailable or LAErrorTouchIdNotEnrolled and you will be able to detect Touch ID presence/state.

If users have disabled passcode on phone with Touch ID, they knew that they will not be able to use Touch ID, so the apps don't need to detect Touch ID presence or promote Touch ID based features. "

So..... the final answer from Apple is No. :(

Note: similar StackOverflow question from the person who reported this -> iOS8 check if device has Touch ID (wonder why I didn't find this question before despite my extensive searching...)