如何使用我的 Xamarinapp 从 FTP 服务器下载文件？

Question

I'm new to Xamarin development. I hope that you can resolve my problem in a simple mode.

I have a cross-platform app developed with Xamarin. In one page of the app I want to give the possibility to download a file (pdf document) when the user taps a button. How can I do it?

The file is hosted in an FTP server.

Please, if you can, give me a simple solution. Thanks.

This is my button in page.xaml

   <StackLayout BackgroundColor="#2B2B2B" HeightRequest="60" Orientation="Horizontal" Padding="0" Margin="0" MinimumWidthRequest="-1">
        <ImageButton VerticalOptions="Center" HorizontalOptions="Start" Source="pdf.png" HeightRequest="50" WidthRequest="50" Margin="10,0,0,0" ></ImageButton>
        <Button VerticalOptions="Center" TextColor="White"  BackgroundColor="Transparent" FontSize="20" FontAttributes="Italic" Text="Scarica il PDF"></Button>
</StackLayout>

Answer 1

The System.Net.WebClient can be used cross platform for FTP calls. Here you can find sample code: FtpCloudStorageClient.cs

Have a look at the DownloadFileAsync() function. If you don't need SSL support, you can directly create a WebClient instead of the derrived CustomFtpWebClient . It would look something like this (untested):

public override async Task<byte[]> DownloadFileAsync(string ftpUrl, string username, string password)
{
    byte[] responseData;
    using (WebClient webClient = new WebClient())
    {
        webClient.Credentials = new NetworkCredential(username, password);
        responseData = await webClient.DownloadDataTaskAsync(ftpUrl);
    }
    return responseData;
}