To resolve device item, you can use this:

var deviceItem = Sitecore.Data.Items.DeviceItem.ResolveDevice(pageItem.Database);

Then you can use one of the approaches below:

1. Sitecore.Context.Device = deviceItem; // doesn't validate deviceItem
2. Sitecore.Context.Data.Device = deviceItem; // validates deviceItem
3. using(new DeviceSwitcher(deviceItem)) { // you code here }

You also can use the switchers below (if needed) to switch Context.Database and Context.Item if they are null:

1. using (new DatabaseSwitcher(pageItem.Database)) {}
2. using (new ContextItemSwitcher(pageItem)) {}

To resolve device item, you can use this:

var deviceItem = Sitecore.Data.Items.DeviceItem.ResolveDevice(pageItem.Database);

Then you can use one of the approaches below:

1. Sitecore.Context.Device = deviceItem; // doesn't validate deviceItem
2. Sitecore.Context.Data.Device = deviceItem; // validates deviceItem
3. using(new DeviceSwitcher(deviceItem)) { /*your code here*/ }

You also can use the switchers below (if needed) to switch Context.Database and Context.Item if they are null:

1. using (new DatabaseSwitcher(pageItem.Database)) {}
2. using (new ContextItemSwitcher(pageItem)) {}

To resolve device item, you can use this:

var deviceItem = Sitecore.Data.Items.DeviceItem.ResolveDevice(pageItem.Database);

Then you can use one of the approaches below:

1. Sitecore.Context.Device = deviceItem; // doesn't validate deviceItem
2. Sitecore.Context.Data.Device = deviceItem; // validates deviceItem
3. using(new DeviceSwitcher(deviceItem)) { // you code here }

To resolve device item, you can use this:

var deviceItem = Sitecore.Data.Items.DeviceItem.ResolveDevice(pageItem.Database);

Then you can use one of the approaches below:

1. Sitecore.Context.Device = deviceItem; // doesn't validate deviceItem
2. Sitecore.Context.Data.Device = deviceItem; // validates deviceItem
3. using(new DeviceSwitcher(deviceItem)) { // you code here }

You also can use the switchers below (if needed) to switch Context.Database and Context.Item if they are null:

1. using (new DatabaseSwitcher(pageItem.Database)) {}
2. using (new ContextItemSwitcher(pageItem)) {}