Class InfiniteQueryViewModel<TArgs, TData, TPageParam>

Namespace

DotNetQuery.Mvvm

Assembly

DotNetQuery.Mvvm.dll

An INotifyPropertyChanged view model wrapping an IInfiniteQuery<TArgs, TData, TPageParam> for MVVM-based UI frameworks (MAUI, WPF, WinUI, UNO, Avalonia). Exposes the paginated query state as bindable properties and marshals all change notifications onto the UI thread via an IUiDispatcher.

The view model holds a live subscription to State for its entire lifetime — this is what keeps the underlying cache entry retained and triggers deferred stale fetches. Dispose the view model when its page is torn down; a forgotten dispose keeps the cache entry alive indefinitely.

Pages are not flattened: TData is a single page and is not necessarily enumerable. Flatten in the owning page view model, e.g. by syncing an ObservableCollection<T> from Pages off StateChanged.

public class InfiniteQueryViewModel<TArgs, TData, TPageParam> : BindableBase, INotifyPropertyChanged, IDisposable where TData : class

Type Parameters

TArgs

The type of the parameters passed to the fetcher.

TData

The type of a single page of data. Constrained to reference types.

TPageParam

The type of the page parameter (cursor/offset).

Inheritance

object

BindableBase

InfiniteQueryViewModel<TArgs, TData, TPageParam>

Implements

INotifyPropertyChanged

IDisposable

Inherited Members

BindableBase.PropertyChanged

BindableBase.RaisePropertyChanged(string)

BindableBase.SetProperty<T>(ref T, T, string)

object.Equals(object)

object.Equals(object, object)

object.GetHashCode()

object.GetType()

object.MemberwiseClone()

object.ReferenceEquals(object, object)

object.ToString()

Constructors

InfiniteQueryViewModel(IInfiniteQuery<TArgs, TData, TPageParam>, IUiDispatcher?)

Wraps an existing infinite query. The view model does not take ownership: Dispose() releases only the view model's own state subscription, and the caller remains responsible for disposing query.

public InfiniteQueryViewModel(IInfiniteQuery<TArgs, TData, TPageParam> query, IUiDispatcher? dispatcher = null)

Parameters

query IInfiniteQuery<TArgs, TData, TPageParam>

The infinite query to wrap.

dispatcher IUiDispatcher

The UI-thread dispatcher. When null, Current is captured; construct the view model on the UI thread or pass a dispatcher explicitly.

InfiniteQueryViewModel(IQueryClient, InfiniteQueryOptions<TArgs, TData, TPageParam>, IUiDispatcher?)

Creates a new infinite query observer via CreateInfiniteQuery<TArgs, TData, TPageParam>(InfiniteQueryOptions<TArgs, TData, TPageParam>) and wraps it. The view model owns the created query and disposes it in Dispose(). This is the recommended path for page view models that receive an IQueryClient through dependency injection.

public InfiniteQueryViewModel(IQueryClient client, InfiniteQueryOptions<TArgs, TData, TPageParam> options, IUiDispatcher? dispatcher = null)

Parameters

client IQueryClient

The query client used to create the observer.

options InfiniteQueryOptions<TArgs, TData, TPageParam>

The infinite query options.

dispatcher IUiDispatcher

The UI-thread dispatcher. When null, Current is captured; construct the view model on the UI thread or pass a dispatcher explicitly.

Properties

CancelCommand

Triggers Cancel(). Enabled while any fetch is in flight.

public ICommand CancelCommand { get; }

Property Value

ICommand

CurrentState

The raw state snapshot, for bindings and converters that need the whole state.

public InfiniteQueryState<TData, TPageParam> CurrentState { get; }

Property Value

InfiniteQueryState<TData, TPageParam>

Error

The exception from the most recent failed fetch. null when not in a failure state.

public Exception? Error { get; }

Property Value

Exception

FetchNextPageCommand

Triggers FetchNextPage(). Enabled only when HasNextPage is true and no fetch is currently in flight.

public ICommand FetchNextPageCommand { get; }

Property Value

ICommand

FetchPreviousPageCommand

Triggers FetchPreviousPage(). Enabled only when HasPreviousPage is true and no fetch is currently in flight.

public ICommand FetchPreviousPageCommand { get; }

Property Value

ICommand

HasData

true when at least one page has been successfully loaded.

public bool HasData { get; }

Property Value

bool

HasError

true when Error is not null.

public bool HasError { get; }

Property Value

bool

HasNextPage

true when a next page is available to fetch.

public bool HasNextPage { get; }

Property Value

bool

HasPreviousPage

true when a previous page is available to fetch.

public bool HasPreviousPage { get; }

Property Value

bool

IsFailure

true when the most recent fetch failed.

public bool IsFailure { get; }

Property Value

bool

IsFetching

true while a full refetch is in flight. See IsFetchingNextPage and IsFetchingPreviousPage for pagination fetches, which do not set this.

public bool IsFetching { get; }

Property Value

bool

IsFetchingNextPage

true while a next-page fetch is in progress. Existing pages remain visible.

public bool IsFetchingNextPage { get; }

Property Value

bool

IsFetchingPreviousPage

true while a previous-page fetch is in progress. Existing pages remain visible.

public bool IsFetchingPreviousPage { get; }

Property Value

bool

IsIdle

true when the query is idle.

public bool IsIdle { get; }

Property Value

bool

IsLoading

true only during the first load — fetching with no pages loaded yet. Bind a full-page loading indicator to this and a subtle refresh indicator to IsFetching.

public bool IsLoading { get; }

Property Value

bool

IsSuccess

true when the most recent fetch succeeded.

public bool IsSuccess { get; }

Property Value

bool

PageParams

The page parameters used to fetch each page in Pages. PageParams[i] was the parameter used to fetch Pages[i].

public IReadOnlyList<TPageParam> PageParams { get; }

Property Value

IReadOnlyList<TPageParam>

Pages

All currently loaded pages, ordered from oldest to newest.

public IReadOnlyList<TData> Pages { get; }

Property Value

IReadOnlyList<TData>

Query

The wrapped query — the escape hatch for members without a bindable counterpart (Invalidate(), Detach(), or direct Rx composition via Success, Failure, Settled).

public IInfiniteQuery<TArgs, TData, TPageParam> Query { get; }

Property Value

IInfiniteQuery<TArgs, TData, TPageParam>

RefetchCommand

Triggers Refetch() for the whole page set. Disabled while any fetch is in flight.

public ICommand RefetchCommand { get; }

Property Value

ICommand

Status

The current lifecycle status of the query.

public QueryStatus Status { get; }

Property Value

QueryStatus

Methods

Dispose()

Releases the view model's state subscription — which lets the cache entry's eviction clock start — and disposes the wrapped query if this view model created it.

public void Dispose()

Dispose(bool)

Releases resources. Override in derived view models to dispose additional state; always call the base implementation.

protected virtual void Dispose(bool disposing)

Parameters

disposing bool

true when called from Dispose().

SetArgs(TArgs)

Sets the args that drive the cache key and fetching. When args change, the query switches to the cache entry for the newly derived key and triggers a fetch if the query is enabled.

public void SetArgs(TArgs args)

Parameters

args TArgs

SetEnabled(bool)

Enables or disables the query. When false, fetching is suspended even if the query is invalidated or new args are pushed. Pass true to resume.

public void SetEnabled(bool enabled)

Parameters

enabled bool

Events

StateChanged

Raised on the UI thread after every PropertyChanged notification for an applied state. Use this — instead of a second raw subscription to Query's state — for page-specific work such as syncing an ObservableCollection<T> from Pages.

public event EventHandler? StateChanged

Event Type

EventHandler