maui-permissions

.NET MAUI Permissions — Gotchas & Best Practices

Critical Anti-Patterns

1. Requesting without checking first

// ❌ Shows prompt even if already granted
var status = await Permissions.RequestAsync<Permissions.Camera>();

// ✅ Check first — avoids unnecessary prompts
var status = await Permissions.CheckStatusAsync<Permissions.Camera>();
if (status != PermissionStatus.Granted)
    status = await Permissions.RequestAsync<Permissions.Camera>();

2. Calling permissions in a constructor

Permission APIs are async and require a UI context. Constructors can't await.

// ❌ Blocks the UI thread or throws
public MyViewModel()
{
    var status = Permissions.RequestAsync<Permissions.Camera>().Result;
}

// ✅ Use OnAppearing, a command, or async initialization
protected override async void OnAppearing()
{
    await CheckAndRequestPermissionAsync<Permissions.Camera>();
}

3. Ignoring Denied and Restricted status

// ❌ Only checks for Granted — misses edge cases
if (status == PermissionStatus.Granted) { /* proceed */ }

// ✅ Handle all relevant statuses
switch (status)
{
    case PermissionStatus.Granted: /* proceed */ break;
    case PermissionStatus.Limited: /* iOS partial access */ break;
    case PermissionStatus.Denied:
    case PermissionStatus.Restricted:
        await ShowSettingsPromptAsync(); break;
}

Platform Pitfalls

⚠️ iOS: One-shot permission dialog

iOS shows the system permission dialog only once per permission, ever. After denial, RequestAsync returns Denied immediately without showing UI. You must guide the user to Settings → App → Permission.

⚠️ Android: ShouldShowRationale timing

ShouldShowRationale returns true only after a prior denial (but not after "Don't ask again"). Use it to show explanatory UI before re-requesting:

if (Permissions.ShouldShowRationale<Permissions.Camera>())
{
    await Shell.Current.DisplayAlert("Permission needed",
        "Camera access is required to scan barcodes.", "OK");
}
status = await Permissions.RequestAsync<Permissions.Camera>();

⚠️ Android API 33+: StorageRead/StorageWrite are dead

On Android 13+, StorageRead and StorageWrite always return Granted (scoped storage makes them meaningless). Use granular media permissions instead:

// ❌ Always returns Granted on API 33+ — gives false confidence
await Permissions.RequestAsync<Permissions.StorageRead>();

// ✅ Use the specific media permission
await Permissions.RequestAsync<Permissions.Photos>();       // photo access
await Permissions.RequestAsync<Permissions.Media>();         // audio/video

⚠️ Windows: Most permissions always return Granted

Windows doesn't have runtime permission dialogs for most features. Declare capabilities in Package.appxmanifest instead.

Always-Check-Before-Request Pattern

The recommended pattern handles iOS one-shot and Android rationale:

public async Task<PermissionStatus> CheckAndRequestPermissionAsync<T>()
    where T : Permissions.BasePermission, new()
{
    var status = await Permissions.CheckStatusAsync<T>();
    if (status == PermissionStatus.Granted)
        return status;

    if (status == PermissionStatus.Denied && DeviceInfo.Platform == DevicePlatform.iOS)
        return status; // iOS won't show dialog again

    if (Permissions.ShouldShowRationale<T>())
    {
        await Shell.Current.DisplayAlert("Permission needed",
            "This feature requires the requested permission.", "OK");
    }

    return await Permissions.RequestAsync<T>();
}

Checklist

• CheckStatusAsync called before every RequestAsync
• No permission calls in constructors — use OnAppearing or commands
• All PermissionStatus values handled (Denied, Restricted, Limited)
• Android: ShouldShowRationale shown before re-requesting
• iOS: Settings navigation provided for denied permissions
• Android API 33+: using Photos/Media instead of StorageRead/StorageWrite
• Manifest/plist declarations match runtime permission requests