NET MAUI V8.0 App - Issues with XAML page and await client.GetObjectAsync() for AWS S3 bucket

Riffy 276

Hello,

I am working on a NET MAUI V8 App that uses AWS S3 for file access. However, I am experiencing weird behavior when executing the following line of code:

using (GetObjectResponse response = await client.GetObjectAsync(request).ConfigureAwait(false))

This happens on all of my pages where I use the S3 code. Once the xaml page is displayed, the subsequent lines are processed. I don't want the page to appear as there is more code to be processed. Here's an extract of the code I'm using:

 using var client = new AmazonS3Client("test", "test", Amazon.RegionEndpoint.USEast1);
var bucketName = "mybucket";
var keyName = "myfile.txt";

GetObjectRequest request = new GetObjectRequest
{
    BucketName = bucketName,
    Key = keyName,
};

using (GetObjectResponse response = await client.GetObjectAsync(request).ConfigureAwait(false))
    using (Stream responseStream = response.ResponseStream)
    using (StreamReader reader = new StreamReader(responseStream))
    {
        string inputString;
        string line = "";
        while ((inputString = await reader.ReadLineAsync().ConfigureAwait(false)) != null)
        {
            string[] parts = inputString.Split('#');
             AddParts();
        }
        reader.Close();
    }

Not sure what is causing this issue so any help would be welcome.

Thanks

Wenyan Zhang (Shanghai Wicresoft Co,.Ltd.) 28,321 Reputation points Microsoft Vendor

2024-03-15T07:17:46.97+00:00

Once the xaml page is displayed, the subsequent lines are processed.

How did you load the xaml page? Which method did you put the code snippets above in ?

Riffy 276

Hi Wenyan

The following is the relevant code:

HomePage.xaml:

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:local="clr-namespace:Myproject.ViewModels" 
             x:Class="WaezCollection.Views.HomePage"
             Title="Home">
    <ContentPage.BindingContext>
        <local:HomeViewModel/>
    </ContentPage.BindingContext>
    <StackLayout >
        <StackLayout  Padding="30">
            <Grid>
                <Grid.RowDefinitions>
                    <RowDefinition Height="100" />
                    <RowDefinition Height="70" />
                </Grid.RowDefinitions>
                <Grid.ColumnDefinitions>
                    <ColumnDefinition Width="*" />
                </Grid.ColumnDefinitions>
                <Image Source="applogo.png" Grid.Row="1" Grid.Column="0" HeightRequest="{OnIdiom 450, Tablet=450, Phone=350}" HorizontalOptions="CenterAndExpand" VerticalOptions="CenterAndExpand" ></Image>
            </Grid>
            <Grid>
                <Grid.RowDefinitions>
                    <RowDefinition Height="*" />
                    <RowDefinition Height="*" />
                    <RowDefinition Height="*" />
                    <RowDefinition Height="*" />
                    <RowDefinition Height="*" />
                    <RowDefinition Height="*" />
                </Grid.RowDefinitions>
                <Grid.ColumnDefinitions>
                    <ColumnDefinition Width="*" />
                    <ColumnDefinition Width="*" />
                    <ColumnDefinition Width="*" />
                    <ColumnDefinition Width="*" />
                    <ColumnDefinition Width="*" />
                </Grid.ColumnDefinitions>
                <Label Text="Records Count: " Grid.Row="2" Grid.Column="0" TextColor="Blue" FontAttributes="Bold" FontSize="11" ></Label>
                <Label Grid.Row="2" Grid.Column="2" Grid.ColumnSpan="1" Text="{Binding TextCnt}"  HorizontalOptions="CenterAndExpand"
                       TextColor="Red" FontAttributes="Bold,Italic" FontSize="15" ></Label>
            </Grid>
        </StackLayout>
    </StackLayout>
</ContentPage>

HomePage.xaml.c:

using Myproject.ViewModels;

namespace Myproject.Views;

public partial class HomePage : ContentPage
{
    readonly HomeViewModel _viewModel;
    public HomePage()
	{
        InitializeComponent();
        BindingContext = _viewModel = new HomeViewModel();
    }
}

using Amazon.S3.Model;
using Amazon.S3;
using System.ComponentModel;
using System.Runtime.CompilerServices;
using Myproject.Views;

namespace  Myproject.ViewModels;

public class HomeViewModel : BaseViewModel
{

public HomePage HomePage;

public class IVM : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;
    public void OnPropertyChanged([CallerMemberName] string name = "")
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(name));
    }
}

public HomeViewModel()
{
    _ = GetCount();

}

private async Task GetCount()
{
    using var client = new AmazonS3Client("test", "test1, Amazon.RegionEndpoint.USEast1);

    var bucketName = "mybucket";
    var keyName = "myfilet.txt";

    GetObjectRequest request = new GetObjectRequest
    {
        BucketName = bucketName,
        Key = keyName,
    };

    using (GetObjectResponse response = await client.GetObjectAsync(request).ConfigureAwait(false))
    using (Stream responseStream = response.ResponseStream)
    using (StreamReader reader = new StreamReader(responseStream))
    {
        string Line;
        while ((Line = await reader.ReadLineAsync().ConfigureAwait(false)) != null)
        {
            TextCnt = Line;
			ProcessCnt();
        }
        reader.Close();
    }
}
}

Riffy 276

Hi Wenyan

The following is the relevant code:

HomePage.xaml:

using MyApp.ViewModels;
namespace MyApp.Views;

public partial class HomePage : ContentPage
{
    readonly HomeViewModel _viewModel;
    public HomePage()
	{
        InitializeComponent();
        BindingContext = _viewModel = new HomeViewModel();
    }
}

HomePage.xaml.cs

using MyApp.ViewModels;
namespace MyApp.Views;

public partial class HomePage : ContentPage
{
    readonly HomeViewModel _viewModel;
    public HomePage()
	{
        InitializeComponent();
        BindingContext = _viewModel = new HomeViewModel();
    }
}

HomeViewModel.cs:

using Amazon.S3.Model;
using Amazon.S3;
using System.ComponentModel;
using System.Runtime.CompilerServices;
using MyApp.Views;

namespace MyApp.ViewModels;
public class HomeViewModel : BaseViewModel
{
    public HomePage HomePage;
    public class IVM : INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;
        public void OnPropertyChanged([CallerMemberName] string name = "")
        {
            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(name));
        }
    }
    public HomeViewModel()
    {
        _ = GetCount();
    }
    private async Task GetCount()
    {
        using var client = new AmazonS3Client("Test", "Test", Amazon.RegionEndpoint.USEast1);
        var bucketName = "mybucket";
        var keyName = "myfile.txt";
        GetObjectRequest request = new GetObjectRequest
        {
            BucketName = bucketName,
            Key = keyName,
        };
        using (GetObjectResponse response = await client.GetObjectAsync(request).ConfigureAwait(false))
        using (Stream responseStream = response.ResponseStream)
        using (StreamReader reader = new StreamReader(responseStream))
        {
            string Line;
            while ((Line = await reader.ReadLineAsync().ConfigureAwait(false)) != null)
            {
                TextCnt = Line;
				ProcessCnt();
            }
            reader.Close();
        }
    }
}

The issue occurs in my other Pages as well when S3 is used for file access.

Thanks

1 answer

Wenyan Zhang (Shanghai Wicresoft Co,.Ltd.) 28,321 Reputation points Microsoft Vendor

2024-03-18T06:33:58.2966667+00:00
Hello,

Once the xaml page is displayed, the subsequent lines are processed.

The subsequent lines (using (GetObjectResponse response = await client.GetObjectAsync(request).ConfigureAwait(false))) are put in GetCount method in your ViewModel(HomeViewModel) class, and you call this method in the constructor of HomeViewModel, which means that this method is called when you create a HomeViewModel object, and the HomeViewModel object isn't created until this method has run.

I don't want the page to appear as there is more code to be processed.

You could call the method in Page.OnAppearing method (or Page.Loaded Event) instead of the constructor of ViewModel.

For example:

Page

protected override async void OnAppearing() { base.OnAppearing(); HomeViewModel homeViewModel = this.BindingContext as HomeViewModel; await homeViewModel.GetCount(); }

ViewMode l(I've omitted some methods)

public class HomeViewModel :... { public HomeViewModel() { // _ = GetCount(); } public async Task GetCount() { ... } }

Best Regards,

Wenyan Zhang

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NET MAUI V8.0 App - Issues with XAML page and await client.GetObjectAsync() for AWS S3 bucket

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