Xamarin: how to backup/sync a sqlite database with DropBox or Google Drive

Question

I have an app written using Xamarin for Android that allows me to store my customers info. I store all the data locally using sqlite and it all works fine. But I need to share this info with my colleague who is using the same app on his phone. So for example, if I add a new customer order from my phone this will be saved into my local db. Now I want to hit a button to trigger the sync of my local db with some backup of this db stores in a shared folder in Dropbox or Google Drive.,

From suggestions below, I am trying to use DropBox Core Api. I got to the point where I authenticate to access my account, now I need to copy my local DB in my app folder in Dropbox. I am using the code below for my second activity. When it launches, I get the authentication page for Dropbox. After that when I click the backup button I am expecting to read the local DB and save it to Dropbox under ./Apps/ClientsApp/. But I only get a generic error (An unhandled exception occured). Where am I making a mistake?

using Dropbox.CoreApi;
using Dropbox.CoreApi.Android;
using Dropbox.CoreApi.Android.Session;

namespace my_app
{
[Activity(Label = "Second Activity")]
class clientsDB : Activity
{
    string AppKey = "myAppKey";
    string AppSecret = "myAppSecret";
    DropboxApi dropboxApi;
    private Button backup;

    protected override void OnCreate(Bundle savedInstanceState)
    {
        base.OnCreate(savedInstanceState);
        SetContentView(Resource.Layout.clientsDB);

        // dropbox
        AppKeyPair appKeys = new AppKeyPair(AppKey, AppSecret);
        AndroidAuthSession session = new AndroidAuthSession(appKeys);
        dropboxApi = new DropboxApi(session);

        (dropboxApi.Session as AndroidAuthSession).StartOAuth2Authentication(this);

        backup = FindViewById<Button>(Resource.Id.backup);
        backup.Click += Backup_Click;
    }


    private void Backup_Click(object sender, EventArgs e)
    {
        string origin = System.IO.Path.Combine(System.Environment.GetFolderPath(System.Environment.SpecialFolder.Personal), "dbClients.db3");

        string dropboxPath = @"./Apps/ClientsApp";
        upload(origin, dropboxPath);

    }

    // use async cause I had Android.OS.NetworkOnMainThreadException 
    async void upload(string origin, string destination)
    {            
        using (var input = File.OpenRead(origin))
        {
            // Gets the local file and upload it to Dropbox
            dropboxApi.PutFile(destination, input, input.Length, null, null);
        }
    }

    protected async override void OnResume()
    {
        base.OnResume();

        // After you allowed to link the app with Dropbox,
        // you need to finish the Authentication process
        var session = dropboxApi.Session as AndroidAuthSession;
        if (!session.AuthenticationSuccessful())
            return;

        try
        {
            // Call this method to finish the authentication process
            session.FinishAuthentication();
        }
        catch (IllegalStateException ex)
        {
            Toast.MakeText(this, ex.LocalizedMessage, ToastLength.Short).Show();
        }
    }


}
}

Answer 1

You need to retrieve your database file first. You can do it as follows:

File dbFile = new File(System.IO.Path.Combine(System.Environment.GetFolderPath‌​(Syst‌​em.Environmen‌​t.Speci‌​alFolder.Pe‌​rsonal), "myDB.db3"));

After you have dbFile variable, you can copy it to SD card or export to Dropbox/GDrive. See this answer for more details on exporting it to Dropbox.

EDIT: Dropbox API mentioned in the answer I linked seems to be deprecated, here's the component for Xamarin: https://components.xamarin.com/view/dropboxcoreapiandroid

EDIT:

If you want to copy your database file to external storage (e.g. SD card), you need to add necessary permissions for your Android app.

In order to be able to write a file in such location, you need to add WRITE_EXTERNAL_STORAGE permission to your app. You can do it by going to your Android project -> Properties -> "Android Manifest" tab -> In section "Required permissions" select WRITE_EXTERNAL_STORAGE. You can also select READ_EXTERNAL_STORAGE to be able to read and write to/from external storage.