Downloading files with Mega API in .NET MAUI on Android

Question

I'm trying to download an image from a remote public Mega folder to an Android device using the Mega API in .NET MAUI.

This is the code:

namespace Junior_Jobs;

using Google.Apis.Auth.OAuth2;
using Google.Apis.Drive.v3;
using Google.Apis.Services;
using CG.Web.MegaApiClient;
using Microsoft.Maui.Controls.PlatformConfiguration;
using Android.OS;
using System;

public partial class Tryimportimage : ContentPage
{
    public Tryimportimage()
    {
        InitializeComponent();
        MegaApiClient client = new MegaApiClient();
        client.LoginAnonymous();

        Uri fileLink = new Uri("https://mega.nz/file/W0UAgJaK#XOYyTETrIy8daz3_dw3fdh6Hh8EFEdrnbyoop1r9R6g");
        INode node = client.GetNodeFromLink(fileLink);

        System.Diagnostics.Debug.WriteLine($"Downloading {node.Name}");
        client.DownloadFileAsync(fileLink, Path.Combine("/storage/emulated/0/Downloads",node.Name));
        
        client.Logout();
    }
}

I don't get any errors at the moment, but the code doesn't do anything either.

Answer 1

First of all, you should neither execute asynchronous code nor do any heavy lifting inside of constructors.

Secondly, you should await the DownloadFileAsync() method:

await client.DownloadFileAsync(fileLink, Path.Combine("/storage/emulated/0/Downloads",node.Name));

Since this cannot be done inside the constructor, because constructors in C# cannot be asynchronous, you'll have to move the code into an async method instead:

namespace Junior_Jobs;

using Google.Apis.Auth.OAuth2;
using Google.Apis.Drive.v3;
using Google.Apis.Services;
using CG.Web.MegaApiClient;
using Microsoft.Maui.Controls.PlatformConfiguration;
using Android.OS;
using System;
using System.Threading.Tasks;

public partial class Tryimportimage : ContentPage
{
    public Tryimportimage()
    {
        InitializeComponent();
    }

    public async Task DownloadAsync()
    {
        MegaApiClient client = new MegaApiClient();
        client.LoginAnonymous();

        Uri fileLink = new Uri("https://mega.nz/file/W0UAgJaK#XOYyTETrIy8daz3_dw3fdh6Hh8EFEdrnbyoop1r9R6g");
        INode node = client.GetNodeFromLink(fileLink);

        System.Diagnostics.Debug.WriteLine($"Downloading {node.Name}");
        await client.DownloadFileAsync(fileLink, Path.Combine("/storage/emulated/0/Downloads",node.Name));
        
        client.Logout();
    }
}

Then you can instantiate the Tryimportimage page and await the result, e.g. like this, depending on how you create your page:

public async Task OpenImportPageAsync()
{
    var page = new Tryimportimage();
    await Navigation.PushAsync(page);
    await page.DownloadAsync();
}

Finally, downloading files and such should usually be delegated to service classes or ViewModels. It's not a common approach to do this directly in a View's code-behind.

You may want to read about asynchronous programming using the async-await pattern.