### Register IDataLoaderBuilderFactory with Dependency Injection

Source: https://github.com/nventive/chinook.dataloader/blob/main/README.md

This snippet demonstrates how to register an IDataLoaderBuilderFactory with Microsoft.Extensions.DependencyInjection for use with ViewModels in Chinook.DynamicMvvm. It shows the setup within a HostBuilder.

```csharp
var serviceProvider = new HostBuilder()
  .ConfigureServices(serviceCollection => serviceCollection
    .AddSingleton<IDataLoaderBuilderFactory, IDataLoaderBuilderFactory>()
  )
  .Build()
  .Services;
```

--------------------------------

### Load Data on a Background Thread

Source: https://github.com/nventive/chinook.dataloader/blob/main/README.md

This example shows how to configure an IDataLoader to execute its load function on a background thread using IDataLoaderBuilder.OnBackgroundThread. This is beneficial for preventing UI thread blocking during data loading.

```csharp
public IDataLoader<string> Stuff => this.GetDataLoader(LoadStuff, b => b
    // Invoke the load from a new task.
    .OnBackgroundThread()
);
```

--------------------------------

### Dispose Previous Data in DataLoader

Source: https://github.com/nventive/chinook.dataloader/blob/main/README.md

This example shows how to configure an IDataLoader to automatically dispose of its previous data when new data is loaded. This is useful when the data itself implements IDisposable or is an IEnumerable of IDisposable items.

```csharp
public IDataLoader<DadJokesItemViewModel[]> Jokes => this.GetDataLoader(LoadJokes, b => b
    // Dispose the previous ItemViewModels when Jokes produces new values.
    .DisposePreviousData()
);
```

--------------------------------

### Mermaid: Initial Data Loading State Flow

Source: https://github.com/nventive/chinook.dataloader/blob/main/README.md

Illustrates the state transitions for initial data loading, from an idle state to loading, and finally to displaying data.

```mermaid
stateDiagram-v2
  direction LR
  s1: IsLoading(false)<br>Data(null)<br>Error(null)
  s2: <b>IsLoading(true)</b><br>Data(null)<br>Error(null)
  s3: IsLoading(false)<br><b>Data(myData)</b><br>Error(null)

  s1 --> s2 : Start loading
  s2 --> s3 : Receive data
```

--------------------------------

### Load Data with Request and Context (C#)

Source: https://github.com/nventive/chinook.dataloader/blob/main/README.md

Demonstrates how to access the source trigger and context from an IDataLoaderRequest within a data loading function. It shows how to read and write to the context, and includes a placeholder for the asynchronous data loading operation.

```C#
Task<MyData> LoadData(CancellationToken ct, IDataLoaderRequest request)
{
  // This is the trigger that caused that loading operation.
  var sourceTrigger = request.SourceTrigger;

  // This is the context that was passed to the loading operation from the trigger.
  var context = request.Context;

  // You can read and write using the context.
  context["myMessage"] = "Hello!";

  // Your async operation here.
}
```

--------------------------------

### Add DataLoader Factory with Default Behaviors (C#)

Source: https://github.com/nventive/chinook.dataloader/blob/main/README.md

Demonstrates how to create an IDataLoaderBuilderFactory with default behaviors like running on a background thread and providing an empty selector using Microsoft.Extensions.DependencyInjection. The factory is registered as a singleton in the service collection.

```csharp
private static IServiceCollection AddDataLoaderFactory(this IServiceCollection services)
{
  return services.AddSingleton<IDataLoaderBuilderFactory>(s =>
  {
    return new DataLoaderBuilderFactory(b => b
      .OnBackgroundThread()
      .WithEmptySelector(GetIsEmpty)
    );

    bool GetIsEmpty(IDataLoaderState state)
    {
      return state.Data == null || (state.Data is IEnumerable enumerable &&    !enumerable.Cast<object>().Any());
    }
  });
}
```

--------------------------------

### C#: Configure DataLoader Empty State

Source: https://github.com/nventive/chinook.dataloader/blob/main/README.md

Shows how to configure a DataLoader to determine if the content is empty using a custom selector based on the state's data.

```csharp
MyAsyncList = DataLoaderBuilder<List<int>>
  .Empty
  .WithName("MyAsyncList")
  .WithLoadMethod(LoadMyAsyncList)
  .WithEmptySelector(state => state.Data is null || state.Data.Count == 0)
  .Build();
```

--------------------------------

### Initialize DataLoader in ViewModel (C#)

Source: https://github.com/nventive/chinook.dataloader/blob/main/README.md

Demonstrates how to initialize an IDataLoader in a ViewModel using DataLoaderBuilder. It includes setting a name, defining a load method, and building the data loader instance. The load method is an async task that simulates data fetching.

```csharp
public MainPageViewModel()
{
  MyAsyncValue = DataLoaderBuilder<int>
    .Empty
    .WithName("MyAsyncValue")
    .WithLoadMethod(LoadMyAsyncValue)
    .Build();
}

public IDataLoader<int> MyAsyncValue { get; }

private async Task<int> LoadMyAsyncValue(CancellationToken ct, IDataLoaderRequest request)
{
   // Your async operation here.
   await Task.Delay(1000, ct);
   return default(int);
}
```

--------------------------------

### Implementing Async Data Loading

Source: https://github.com/nventive/chinook.dataloader/blob/main/README.md

This C# code shows the required signature for the Load function within an IDataLoader. It should return a Task of the data type and accept a CancellationToken for cancellation.

```C#
async Task<MyData> LoadData(CancellationToken ct, IDataLoaderRequest request)
{
  // Put your async operation here.
  return default(MyData);
}
```

--------------------------------

### Using DataLoaderView in XAML

Source: https://github.com/nventive/chinook.dataloader/blob/main/README.md

This XAML snippet demonstrates how to integrate the DataLoaderView into your application. It binds to an asynchronous data source and includes a DataTemplate for displaying the loaded data.

```XAML
<!-- Add the DataLoaderView namespace: xmlns:dl="using:Chinook.DataLoader" -->
<dl:DataLoaderView Source="{Binding MyAsyncValue}"
                   Style="{StaticResource DefaultDataLoaderViewStyle}">
  <DataTemplate>
    <StackPanel>
      <TextBlock Text="{Binding Data}" />
    </StackPanel>
  </DataTemplate>
</dl:DataLoaderView>
```

--------------------------------

### Mermaid: Data Refresh with Network Error State Flow

Source: https://github.com/nventive/chinook.dataloader/blob/main/README.md

Demonstrates state changes during a pull-to-refresh action when a network error occurs, preserving previous data.

```mermaid
stateDiagram-v2
  direction LR
  s3: IsLoading(false)<br>Data(myData)<br>Error(null)
  s4: <b>IsLoading(true)</b><br>Data(myData)<br>Error(null)
  s5: IsLoading(false)<br>Data(myData)<br><b>Error(WebException)</b>

  s3 --> s4 : Start refresh
  s4 --> s5 : Receive error<br>because not network
```

--------------------------------

### DataLoaderView with Throttling

Source: https://github.com/nventive/chinook.dataloader/blob/main/README.md

This XML snippet demonstrates how to configure the DataLoaderView with properties to manage UI flickering. StateMinimumDuration sets the minimum time a visual state is displayed, while StateChangingThrottleDelay controls the delay before updating to a new state, preventing unnecessary loading indicators.

```XML
<dl:DataLoaderView Source="{Binding MyDataLoader}"
                   StateMinimumDuration="0:0:1.5"
                   StateChangingThrottleDelay="0:0:0.100" />
```

--------------------------------

### DataLoaderView XAML Templates and Style (XML)

Source: https://github.com/nventive/chinook.dataloader/blob/main/README.md

Provides XAML code for defining templates and a default style for DataLoaderView. This includes templates for empty states, error notifications, and error states, along with a comprehensive style that configures visual state management and template assignments.

```xml
<DataTemplate x:Key="DataLoaderViewEmptyTemplate">
        <Grid>
            <TextBlock Text="Nothing to show here"
                        HorizontalAlignment="Center"
                        VerticalAlignment="Top"
                        Margin="0,44,0,0" />
        </Grid>
    </DataTemplate>

    <DataTemplate x:Key="DataLoaderViewErrorNotificationTemplate">
        <Grid Background="#570000"
              VerticalAlignment="Bottom"
              Padding="8">

            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="*" />
                <ColumnDefinition Width="Auto" />
            </Grid.ColumnDefinitions>

            <TextBlock Foreground="White"
                        HorizontalAlignment="Left"
                        VerticalAlignment="Center">
    <Run Text="Something went wrong." />
    <Run Text="{Binding Error.Message}" />
            </TextBlock>

            <!-- Try Again Button -->
            <Button Content="Try Again"
                    Background="#990000"
                    HorizontalAlignment="Center"
                    Command="{Binding View.RefreshCommand}"
                    Grid.Column="1" />
        </Grid>
    </DataTemplate>

    <!-- Error State -->
    <DataTemplate x:Key="DataLoaderViewErrorTemplate">
        <Grid>
            <StackPanel VerticalAlignment="Center"
                        HorizontalAlignment="Stretch">

                <!-- Title -->
                <TextBlock Text="Something went wrong"
                            TextAlignment="Center"
                            Margin="0,0,0,8" />

                <!-- Message -->
                <TextBlock Text="Please try again."
                            TextAlignment="Center" />

                <!-- Try Again Button -->
                <Button Content="Reload content"
                        HorizontalAlignment="Stretch"
                        Command="{Binding View.RefreshCommand}"
                        Margin="22,24,22,0" />
            </StackPanel>
        </Grid>
    </DataTemplate>

    <Style x:Key="DefaultDataLoaderViewStyle"
            TargetType="dl:DataLoaderView">
        <Setter Property="IsTabStop"
                Value="False" />
        <Setter Property="HorizontalAlignment"
                Value="Stretch" />
        <Setter Property="VerticalAlignment"
                Value="Stretch" />
        <Setter Property="HorizontalContentAlignment"
                Value="Stretch" />
        <Setter Property="VerticalContentAlignment"
                Value="Stretch" />

        <Setter Property="EmptyTemplate"
                Value="{StaticResource DataLoaderViewEmptyTemplate}" />
        <Setter Property="ErrorTemplate"
                Value="{StaticResource DataLoaderViewErrorTemplate}" />
        <Setter Property="ErrorNotificationTemplate"
                Value="{StaticResource DataLoaderViewErrorNotificationTemplate}" />

        <!-- This represents the minimum duration of a visual state.
    You should keep this high enough to prevent visual states from changing too fast.
    This is the property that prevents flickers. -->
        <Setter Property="StateMinimumDuration"
                Value="0:0:1.5" />

        <!-- This represents the time before updating to a new state during which another update can happen.
    You should keep this low enough to prevent slowing down your user experience.
    This is the property that prevents seeing loading states that are not necessary. -->
        <Setter Property="StateChangingThrottleDelay"
                Value="0:0:0.100" />

        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="dl:DataLoaderView">
                    <Grid>
                        <VisualStateManager.VisualStateGroups>

                            <VisualStateGroup x:Name="DataStates">

```

--------------------------------

### Declare DataLoader using IViewModel.GetDataLoader

Source: https://github.com/nventive/chinook.dataloader/blob/main/README.md

This C# code defines a ViewModel that utilizes Chinook.DynamicMvvm's IViewModel.GetDataLoader to declare an IDataloader. It also shows how to create a command to refresh the data using GetCommandFromDataLoaderRefresh.

```csharp
public class MyViewModel : ViewModelBase
{
  public IDynamicCommand RefreshData => this.GetCommandFromDataLoaderRefresh(Data);

  public IDataLoader Data => this.GetDataLoader(GetData, b => b
    // You can optionally configure your data loader here
  );

  private async Task<MyData> GetData(CancellationToken ct)
  {
    // Get data from your API...
  }
}
```

--------------------------------

### Configure Default Refresh Command for DataLoaderViews (C#)

Source: https://github.com/nventive/chinook.dataloader/blob/main/README.md

Shows how to set a default refresh command provider for all DataLoaderView instances. This involves assigning a function to DataLoaderView.DefaultRefreshCommandProvider that creates a command to reload the DataLoader with a specific context.

```csharp
private void SetupDefaultRefreshCommand(IServiceProvider services)
{
  // DefaultRefreshCommandProvider is just a Func<DataLoaderView, ICommand> that's invoked when a DataLoaderView is created.
  DataLoaderView.DefaultRefreshCommandProvider = GetDataLoaderViewRefreshCommand;

  ICommand GetDataLoaderViewRefreshCommand(DataLoaderView dataLoaderView)
  {
    return services
      .GetRequiredService<IDynamicCommandBuilderFactory>()
      .CreateFromTask(
        name: "DataLoaderViewRefreshCommand",
        execute: async (ct) =>
        {
          var context = new DataLoaderContext();
          // You can add some content to the context.
          context["IsForceRefreshing"] = true;
          await dataLoaderView.DataLoader.Load(ct, context);
        },
        viewModel: (IViewModel)App.Instance.Shell.DataContext)
      .Build();
  }
}
```

--------------------------------

### Dispose Subscriptions with DisposeWithNextLoad

Source: https://github.com/nventive/chinook.dataloader/blob/main/README.md

This C# code illustrates how to manage disposable objects, such as subscriptions from DynamicData, ensuring only one remains active at a time. It uses the IDisposable.DisposeWithNextLoad extension method on an IDataLoaderRequest.

```csharp
public IDataLoader<ReadOnlyObservableCollection<int>> MyList => this.GetDataLoader(LoadMyList);

private async Task<ReadOnlyObservableCollection<int>> LoadMyList(CancellationToken ct, IDataLoaderRequest request)
{
  DynamicData.IObservableList<int> itemsSource = await GetItems(ct);
  itemsSource
    .Connect()
    .Bind(out var list)
    .Subscribe()
    // Dispose this subscription when the next one is created.
    .DisposeWithNextLoad(request);

  return list;
}
```

--------------------------------

### Data Binding Context in XAML (XML)

Source: https://github.com/nventive/chinook.dataloader/blob/main/README.md

Illustrates how to bind to the data context within a ControlTemplate for a DataLoaderView in XAML. It shows how to access the 'myMessage' key from the request context using data binding.

```XML
<ControlTemplate TargetType="dl:DataLoaderView">
  <Grid>
    <!-- (...) -->
    <TextBlock Text="{Binding State.Request.Context[myMessage], RelativeSource={RelativeSource Mode=TemplatedParent}}"/>
  </Grid>
</ControlTemplate>
```

--------------------------------

### Default DataLoaderView Style

Source: https://github.com/nventive/chinook.dataloader/blob/main/README.md

This XAML defines a ControlTemplate for the DataLoaderView, including ContentPresenters for different states (empty, error, error notification) and a ProgressRing for loading indication.

```XAML
<Style TargetType="{x:Type dl:DataLoaderView}">
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="{x:Type dl:DataLoaderView}">
                        <Grid>
                            <ContentPresenter x:Name="EmptyPresenter"
                                              Content="{TemplateBinding State}"
                                              ContentTemplate="{TemplateBinding EmptyTemplate}"
                                              HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}"
                                              VerticalAlignment="{TemplateBinding VerticalContentAlignment}"
                                              Visibility="Collapsed"
                                              Padding="{TemplateBinding Padding}" />

                            <ContentPresenter x:Name="ErrorPresenter"
                                              Content="{TemplateBinding State}"
                                              ContentTemplate="{TemplateBinding ErrorTemplate}"
                                              HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}"
                                              VerticalAlignment="{TemplateBinding VerticalContentAlignment}"
                                              Visibility="Collapsed"
                                              Padding="{TemplateBinding Padding}" />

                            <ContentPresenter x:Name="ErrorNotificationPresenter"
                                              Content="{TemplateBinding State}"
                                              ContentTemplate="{TemplateBinding ErrorNotificationTemplate}"
                                              HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}"
                                              VerticalAlignment="{TemplateBinding VerticalContentAlignment}"
                                              Visibility="Collapsed"
                                              Padding="{TemplateBinding Padding}" />

                            <ProgressRing x:Name="LoadingIndicator"
                                          Foreground="Black"
                                          Visibility="Collapsed"
                                          IsActive="False"
                                          Width="20"
                                          Height="20"
                                          HorizontalAlignment="Center"
                                          VerticalAlignment="Center" />
                        </Grid>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>
```

--------------------------------

### Re-evaluate IsEmpty on Collection Change

Source: https://github.com/nventive/chinook.dataloader/blob/main/README.md

This snippet demonstrates how to use IDataLoaderBuilder.UpdateOnCollectionChanged to automatically re-evaluate the 'IsEmpty' state of a DataLoader when an associated collection (implementing INotifyCollectionChanged) changes.

```csharp
public IDataLoader<ObservableCollection<ToDoItem>> ToDoList => this.GetDataLoader(LoadToDoList, b => b
    // Re-evaluate is Empty when the collection changes.
    .UpdateOnCollectionChanged()
);
```

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