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Design the infrastructure persistence layer
Repository Pattern

1 Repository per resource: ItemRepository
1 DbContext for the whole application
Repositories/ItemRepository.cs
public class ItemRepository : IItemRepository
{
    private readonly MyAppContext context;

    public ItemRepository(MyAppContext context)
    {
        this.context = context;
    }

    public async Task<IReadOnlyCollection<Item>> GetAllItemsAsync(CancellationToken cancellationToken)
    {
        var items = await context.Items
            .Include(x => x.NavigationProperty)
            .AsNoTracking()
            .ToListAsync(cancellationToken);
        return items;
    }

    public async Task<Item?> GetItemByIdAsync(int id, CancellationToken cancellationToken)
    {
        var item = await context.Items
            .AsNoTracking()
            .SingleOrDefaultAsync(x => x.Id == id, cancellationToken);
        return item;
    }

    public async Task<IReadOnlyCollection<Item>> GetItemsByNameAsync(string name, CancellationToken cancellationToken)
    {
        var items = await context.Items
            .Where(x => EF.Functions.Like(x.Name, $"%{name}%"))
            .AsNoTracking()
            .ToListAsync(cancellationToken);
        return items;
    }

    public async Task<Item> CreateItemAsync(Item item, CancellationToken cancellationToken)
    {
        await context.AddAsync(item, cancellationToken);
        await context.SaveChangesAsync(cancellationToken);
        return item; // it now contains its id
    }

    public async Task<bool> UpdateItemAsync(int id, Item item, CancellationToken cancellationToken)
    {
        ArgumentNullException.ThrowIfNull(item);

        var itemToUpdate = await context.Items.SingleOrDefaultAsync(x => x.Id == id, cancellationToken);

        if (itemToUpdate is null)
        {
            return false; // send not found from controller then
        }

        itemToUpdate.Name = item.Name;
        await context.SaveChangesAsync();
        return true;
    }

    public async Task<bool> DeleteItemAsync(int id, CancellationToken cancellationToken)
    {
        var nbAffectedRows = await context.Items.Where(x => x.Id == id).ExecuteDeleteAsync(cancellationToken);
        return nbAffectedRows == 1;
    }