.NET Maui File Locations

Fritz Switzer 261

I've used code that is similar to the following in my UWP programs:

 string filename = "Northwind.db";  
        bool isExisting = false;  
        try  
        {  
            StorageFile storage = await Application.Current.LocalFolder.GetFileAsync(filename);  
            isExisting = true;  
        }  
        catch (Exception)  
        {  
            isExisting = false;  
        }  
        if (!isExisting)  
        {  
            StorageFile databaseFile = await Package.Current.InstalledLocation.GetFileAsync(filename);  
            await databaseFile.CopyAsync(ApplicationData.Current.LocalFolder, filename, NameCollisionOption.ReplaceExisting);  
        }

but this doesn't work with my .NET Maui program. I am mostly interested in the Windows and Android projects. There are so many different File location options. The key point is I want to use an existing SQLite db with my app.

I've tried to assign the db to MauiAsset, but it goes to a local location.

Yonglun Liu (Shanghai Wicresoft Co,.Ltd.) 42,001 Reputation points Microsoft Vendor

2022-07-27T05:38:24.29+00:00

May I know whether your issue has been solved or not? If not, please share it in here. We can work together to figure it out.
Fritz Switzer 261 Reputation points

2022-07-28T14:39:53.08+00:00

Yonglun,

No, I have not gotten my program to work yet.
I'm having difficulty with the Android app displaying the correct records from a pre-existing SQLite db. No problems with the Windows.

Unfortunately, I have not been able to find on the web any good ,NET Maui examples/samples of using a pre-exisiting db. The examples I've found, usually say something like " this is an Xamarin.Forms sample and it "should" work for Maui".......not the case for me.

I'd like one simple example for .NET Maui (Windows and Android) that uses the correct resources location and loads and displays a simple collection view with data for both Windows and Android.

I'm assuming the "single project" structure for .NET Maui will preclude having to have separate code in different target projects like Xamarin.

Fritz Switzer 261

Here is a snippet that has a working version for the Windows project:

public partial class MainPage : ContentPage  
{  
    private int count = 0;  
  
    public ObservableCollection<Employee> Employees { get; set; } = new ObservableCollection<Employee>();  
  
    public static List<Employee> list = new List<Employee>();  
  
    public MainPage()  
    {  
        InitializeComponent();  
  
        var path = AppDomain.CurrentDomain.BaseDirectory;  
        var fullpath = Path.Combine(path, "chinook.db");  
  
        if (File.Exists(fullpath))  
        {  
            using (var db = new SQLite.SQLiteConnection(fullpath))  
            {  
                try  
                {  
                    list = db.Table<Employee>().ToList();  
                }  
                catch { }  
            }  
        }  
  
        foreach (var employee in list)  
        {  
            Employees.Add(employee);  
        }  
  
        BindingContext = this;  
    }  
}

Here is the screen after running the Windows project:

When I run the Android proj, I get nothing, nada.

Yonglun Liu (Shanghai Wicresoft Co,.Ltd.) 42,001 Reputation points Microsoft Vendor

2022-07-29T05:31:06.883+00:00
When I run the Android proj, I get nothing, nada.

Did the program can't find database file on android or the data list is different from the expected effect? Please provide more detailed information.

In MAUI, we could use FileSystem to access the app's cache and data directories, and helps access files in the app package on different platforms, you could refer File system helpers to get more details.

Referring to this offical course: Store local data with SQLite in a .NET MAUI app, you could use the following code to access your sqliteDB file:

public static string GetLocalFilePath(string filename) { return System.IO.Path.Combine(FileSystem.AppDataDirectory, filename); }
Fritz Switzer 261 Reputation points

2022-07-30T15:24:53.55+00:00
Still, seeing the problem.
I think the issue is with the "adding an asset to the app".

When I add the existing db to the project and assigned it's Build Action to "Maui Asset"/copy If Newer the Windows project executes with no problem.

However, with the app is run, the db doesn't get copied to the correct Android path.

My questions then become:

What is the correct protocol to add an existing SQLite db to a NET Maui solution that includes a Windows and a Android project?

How/where should the db be added to the project so that it gets copied to the correct file location for each working project.

Thanks in advance.
Yonglun Liu (Shanghai Wicresoft Co,.Ltd.) 42,001 Reputation points Microsoft Vendor

2022-08-01T06:03:49.297+00:00
I noticed you used AppDomain.CurrentDomain.BaseDirectory to set the file location. Referring to the official API documentation AppDomain.BaseDirectory Property we could find it is not supported on Android platform.

You could try the following code, I've tested it, and it works fine on both Android and Windows:

In the MainPage.xaml.cs:

var path = FileSystem.AppDataDirectory; var fullpath = Path.Combine(path, "chinook.db"); var repo = new EmployeeRepo("chinook.db");

The EmployeeRepo.cs:

public class EmployeeRepo { public readonly SQLiteConnection database; public EmployeeRepo(string dbName) { var dbPath = Path.Combine(FileSystem.AppDataDirectory, dbName); database = new SQLiteConnection(dbPath); database.CreateTable<Employee>(); } }

In addition, you need to install SQLitePCLRaw.provider.dynamic_cdecl NuGet Package.
Fritz Switzer 261 Reputation points

2022-08-01T15:45:53.397+00:00

Thanks Mr/Miss Liu,

Can you attach your zip/attach your working project?
My existing db gets copied, but is empty, with a blank Employee table.

Never seen that SQLiteRaw NuGet package.... but with 43M installs , it must be kinda important.

thanks in advance.
Yonglun Liu (Shanghai Wicresoft Co,.Ltd.) 42,001 Reputation points Microsoft Vendor

2022-08-02T07:35:03.147+00:00

Due to my policy, I can't provide you with a project package.

Could you please provide a minimal sample and your expected behavior?

I will resolve your issue by my best.

1 answer

Gordon Moore 6 Reputation points

2022-07-23T09:20:51.41+00:00

private static Database.Database database;
private readonly static string filename = "xxx.db3";

public static Database.Database Database
{
get
{
if (database == null)
{
database = new Database.Database(Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData), filename));
}
return database;
}
}

This does work for Android (Taken from gerald Versluis video https://www.youtube.com/watch?v=uxqQqyuZ3Qo&t=1003s

To find the db3 you can use Android Studio and the Device File Explorer - look under Data and then drill down to your company website app name e.g. uk.co.xxxxx.appname

However, I too am quite keen to know about all the different locations, because i'd rather my db3 was in something more accessible.
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