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I'm attempting to get the int resource id for a layout resource by name, using Resources.GetIdentifier() of the Android API, but it returns 0. I'm using c#/monodroid/Xamarin, but regular java Android knowledge would apply too I suspect. Here's my code:

int resId = Resources.GetIdentifier(typeName, "layout", _activity.PackageName);
Where typeName = "FrmMain", and in my project I have the file "Resources/Layout/FrmMain.axml". Any ideas?
This is old, but for everyone getting this problem, I think it is because the resource name should be in lower case, so:
int resId = Resources.GetIdentifier("FrmMain", "layout", _activity.PackageName);
does not work, but:
int resId = Resources.GetIdentifier("frmmain", nameof(Resource.Layout).ToLower(), _activity.PackageName);
should work
edit:

According to this answer, you can (and should) use reflection to achieve what you're after, so I think you would try something like this:  
var resourceId = (int)typeof(Resource.Layout).GetField(typeName).GetValue(null);
which does seem to work on my app and should get what you're after.
                No because I need to look up the resource dynamically; sorry, forgot to mention that. "typeName" could be one of many things. "FrmMain" is just what I'm debugging with currently.
– voxoid
                Dec 3, 2013 at 16:02
                Thanks. This solution does work, and it's the one I had used myself as a work around, but I still don't understand why Resources.GetIdentifier() was not finding the resource; it seems that function is the more "correct" way of getting a resource id dynamically, rather than reflecting on the generated code in Resources. Nevertheless it works.
– voxoid
                Dec 9, 2013 at 14:33
                The code with reflection worked. I was trying to user the Resources.GetIdentifier inside a Fragment. May be thats why it was not working there.
– Aman Sura
                Jul 1, 2016 at 20:30
In my case, this issue came up when I had to upgrade the target SDK due to google's new policy since November, 2018. 
I had to display some strings according to the server response code (ex : api_res_001_suc), but it did not work on the upgraded version.
The overall version, about 22 as I recall, had to be changed to 27.
The cause of the issue seems to be the default translation stuff. When I put all the default translation for every string, it worked. 
My code is,
getResources().getIdentifier(resName, "string", "packageName");
I've created a ResourceHelper class to handle this situation. Here is the code:
public static class ResourceHelper
    public static int FindId(string resourceId)
        var type = typeof(Resource.Id);
        var field = type.GetField(resourceId);
        return (int)field.GetRawConstantValue();
    public static int FindLayout(string layoutName)
        var type = typeof(Resource.Layout);
        var field = type.GetField(layoutName);
        return (int)field.GetRawConstantValue();
    public static int FindMenu(string menuName)
        var type = typeof(Resource.Menu);
        var field = type.GetField(menuName);
        return (int)field.GetRawConstantValue();
Actually I'm improving it because I need to use it from another Assembly and it's restricted to work in the same Assembly of the Droid App. I'm thinking about put a generic method (or an Extension one) to do this. Here is a draft of my idea:
public static int FindResource<T>(string resourceName)
    var type = typeof(T);
    var field = type.GetField(resourceName);
    return (int)field.GetRawConstantValue();
Hope it can help you.
        
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