SQLite, check if Database Exist and have correct data, More efficient way

Question

Im making a Xamarin.Android application and i use SQLite for some images (300+). I store the images as Templates in a group of 5 images like this:

    [Table("Templates")]
    public class Template
    {
        [PrimaryKey, AutoIncrement]
        public int Id { get; set; }
        public string Name { get; set; }
        public int Category { get; set; }
        [OneToMany]
        public List<TemplateImage> TemplateImages { get; set; }
        public string ImagesHash { get; set; }
    }
    [Table("TemplateImages")]
    public class TemplateImage
    {
        [PrimaryKey, AutoIncrement]
        public int Id { get; set; }
        public int Category { get; set; }
        public int Image { get; set; }
        [ForeignKey(typeof(Template))]
        public int TemplateId { get; set; }
    }

And the first time the App is launched i use this code To check if the Database exist or Create the DB:

public static void AddTemplate(int category, List<int> images)
        {
            var tmpl = new Template()
            {
                Category = category,
            };
            if (images != null)
            {
                var img1 = new TemplateImage()
                {
                    Category = category,
                    Image = images[0],
                };
                var img2 = new TemplateImage()
                {
                    Category = category,
                    Image = images[1],
                };
                var img3 = new TemplateImage()
                {
                    Category = category,
                    Image = images[2],
                };
                var img4 = new TemplateImage()
                {
                    Category = category,
                    Image = images[3],
                };
                var img5 = new TemplateImage()
                {
                    Category = category,
                    Image = images[4],
                };
                tmpl.TemplateImages = new List<TemplateImage>() { img1, img2, img3, img4, img5 };
            }
            tmpl.ImagesHash = Guid.NewGuid().ToString();

            DatabaseHelper.Db().InsertAll(tmpl.TemplateImages);
            DatabaseHelper.Db().Insert(tmpl);
            DatabaseHelper.Db().UpdateWithChildren(tmpl);
        }

        public static List<Template> GetAllTemplates()
        {
            return DatabaseHelper.Db().GetAllWithChildren<Template>();
        }

        public static Template GetTemplate(int id)
        {
            var result = DatabaseHelper.Db().GetWithChildren<Template>(id);
            if (result == null)
            {
                result = DatabaseHelper.Db().GetAllWithChildren<Template>().Where(record => record.Category == (int)TemplateCategory.Emojis).OrderBy(record => record.Id).FirstOrDefault();
            }
            return result;
        }

public static void CreateDB()
        {
            DatabaseHelper.Db().RunInTransaction(() =>
            {
                DatabaseHelper.Db().CreateTable<Template>();
                DatabaseHelper.Db().CreateTable<TemplateImage>();
                if (DatabaseHelper.Db().Table<Template>().Count() != 0)
                {
                    return;
                }
                AddTemplate(

                    (int)TemplateCategory.Emojis,
                    new List<int>
                    {
                Resource.Drawable.ic_angry,
                Resource.Drawable.ic_sad,
                Resource.Drawable.ic_neutral,
                Resource.Drawable.ic_happy,
                Resource.Drawable.ic_smiling,
                    }
                );
                AddTemplate(

    (int)TemplateCategory.Emojis,
     new List<int>
                {
                Resource.Drawable.ic_emoji_01_1,
                Resource.Drawable.ic_emoji_01_2,
                Resource.Drawable.ic_emoji_01_3,
                Resource.Drawable.ic_emoji_01_4,
                Resource.Drawable.ic_emoji_01_5,
    }
    );

...//AND many more AddTemplate() functions like those 2.
}

This was working great until i saw one day in a very rare situation that sometimes the application was showing.. other images from those i have select it a random way. So i realised that the compiler for some reasons is deciding to change the ResourceId of the ImageDrawables and so, despite the fact that my DB exist, it is completely wrong,

So i have start thinking again what is the correct way of doing something like that, without recreating every time the database, i found the idea of recreating the DB every time a bad one, but if it is the only correct way and the only way that i can be 100% sure for the result i will keep it.

I have see from my tests that usually the first sets of images are getting changed (The first Templates) and i was thinking if it is a good idea to do something like this:

public static bool ExistingDBItemsFound(int id)
        {
            var returnValue = false;
            var result = GetTemplate(1);
            if (result.TemplateImages.Count == 5)
            {
                if (result.TemplateImages[0].Image == Resource.Drawable.ic_angry
                    && result.TemplateImages[1].Image == Resource.Drawable.ic_sad
                    && result.TemplateImages[1].Image == Resource.Drawable.ic_neutral
                    && result.TemplateImages[1].Image == Resource.Drawable.ic_happy
                    && result.TemplateImages[1].Image == Resource.Drawable.ic_smiling)
                    returnValue = true;
            }
            return returnValue;
        }

But if i do something like this how i can be sure that all the rest of the resource ids are correct? i only checking 5 of 300+.

Can i avoid recreate every time the database items of app creation? i yes how?

Is there a way to save a resource in the database in another format rather than resourceId?

Answer 1

Resource Ids should never be used as a unique identifier as compiler can easily change them some times, so the best approach was to completly avoid using them.

One solution to my problem could be to use the suggested answer from here: Best way to store Resource id in Database on Android

Get icon name

var iconName = Context.Resources.GetResourceEntryName( Resource.Drawable.your_icon );

and then get id from name:

var id = Context.Resources.GetIdentifier( iconName, "drawable", Context.PackageName )

That way, even if Resource Id change, we will get the correct image, as long as we don't rename our resources.

If you want also to check if the user DB has the correct values as your apk DB, you can do something like what @martin venter suggest and create a hash somehow (ex: hash of resource names) and compare them