Chapter 2 Working with Visual Studio 2022
All the moving parts should now be hooked up for our weather application to pull data from the API and return the weather information for Los Angeles, including the ten-day forecast. The next topic that I want to touch on is using SQLite in your MAUI application.
Using SQLite in a MAUI Application
In the previous section, we looked at how to consume an API in a MAUI application. For that reason, I will not step through all the details of this application. I reused the existing weather service application and ripped out everything not applicable to the SQLite functionality we wanted to implement. The SQLite app is a simple to-do application, and the solution is seen in Figure 2-27.
Figure 2-27. The SQLite project structure
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As before, I have a Services folder containing the ToDoService and its IToDoService Interface. I have a Model folder containing the ToDoItem class. Lastly, I have the ViewModel folder with the MainViewModel class. You can see that the project structure follows the same pattern as before. The only difference here is that in addition to the Community Toolkit, I have added additional NuGet packages for SQLite, as seen in Figure 2-28.
Figure 2-28. The SQLite NuGet packages
In the next section, let’s start with creating the model for a to-do item.
The ToDoItem Model
After adding the SQLite NuGet package, I can create the ToDoItem model as seen in Listing 2-11.
Listing 2-11. The ToDoItem Model
using SQLite;
namespace HelloMAUI.Model
{
[Table("todo")] public class ToDoItem
{
[PrimaryKey, AutoIncrement] public int Id { get; set; }
[MaxLength(250)]
public string ToDoText { get; set; }
}
}
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I can now bring in the SQLite namespace, which allows me to add SQLite-specific attributes to my model. This model maps to a table in SQLite called todo because I have added the [Table("todo")] attribute to my class. I can now define additional
attributes on my model properties, in this case, specifying that my Id property is an autoincrementing primary key and that the text that contains the to-do item cannot be longer than 250 characters.
The ToDoService
As with the weather application’s service, we are creating an Interface called IToDoService. The code is in Listing 2-12.
Listing 2-12. The IToDoService Interface
using HelloMAUI.Model;
namespace HelloMAUI.Services
{
public interface IToDoService
{
Task Init();
Task AddToDo(string todoItem); Task<IEnumerable<ToDoItem>> GetToDoItems();
}
}
This defines a contract for each implementing class to provide an implementation for initializing the database, adding to-do items, and reading all the to-do items.
Listing 2-13. The ToDoService
using HelloMAUI.Model; using SQLite;
namespace HelloMAUI.Services
{
public class ToDoService : IToDoService
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{
private SQLiteAsyncConnection _db; readonly string _dbPath;
public ToDoService()
{
_dbPath = Path.Combine(Environment.GetFolderPath(Environment. SpecialFolder.MyDocuments), "mydb.db");
}
public async Task Init()
{
if (_db != null) return;
_db = new SQLiteAsyncConnection(_dbPath); _ = await _db.CreateTableAsync<ToDoItem>();
}
public async Task AddToDo(string todoText)
{
await Init();
var todoItem = new ToDoItem
{
ToDoText = todoText
};
var result = await _db.InsertAsync(todoItem);
}
public async Task<IEnumerable<ToDoItem>> GetToDoItems()
{
await Init();
return await _db.Table<ToDoItem>().ToListAsync();
}
}
}
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