InfiniteAsyncSource.FetchRows Event

Allows you to fetch rows.

Namespace: DevExpress.Xpf.Data

Assembly: DevExpress.Xpf.Core.v21.2.dll

Declaration

public event EventHandler<FetchRowsAsyncEventArgs> FetchRows

Event Data

The FetchRows event's data class is FetchRowsAsyncEventArgs. The following properties provide information specific to this event:

Property Description
AllowRetry Gets or sets whether re-requesting data is allowed. Inherited from FetchRowsEventArgsBase.
Filter Gets the GridControl filtering. Inherited from FetchEventArgsBase.
Keys Gets keys that you passed to the ReloadRows(Object[]) method.
Result Gets or sets the result of the fetch rows operation.
Skip Gets the number of rows to skip in a returned result set. Inherited from FetchEventArgsBase.
SkipToken Gets the skip token. Inherited from FetchEventArgsBase.
SortOrder Gets the GridControl‘s sorting. Inherited from FetchEventArgsBase.
Take

Gets the number of rows within and above the viewport that are reloaded when you call the RefreshRows method or users press F5.

null when the grid fetches next portion of data (a user scrolls rows).

int.Max when you call the InfiniteAsyncSource.ReloadRows / PagedAsyncSource.ReloadRows method.

Inherited from FetchRowsEventArgsBase.

Remarks

View Example: How to Bind to InfiniteAsyncSource

To fetch rows from the data source:

public MainWindow() {
    // ...
    source.FetchRows += (o, e) => {
        e.Result = FetchRowsAsync(e);
    };
}
static async Task<FetchRowsResult> FetchRowsAsync(FetchRowsAsyncEventArgs e) {
  IssueSortOrder sortOrder = GetIssueSortOrder(e);
  IssueFilter filter = MakeIssueFilter(e.Filter);
  var take = e.Take ?? 30;
  var issues = await IssuesService.GetIssuesAsync(
    skip: e.Skip,
    take: take,
    sortOrder: sortOrder,
    filter: filter);
  return new FetchRowsResult(issues, hasMoreRows: issues.Length == take);
}
static IssueSortOrder GetIssueSortOrder(FetchRowsAsyncEventArgs e) {
    return IssueSortOrder.Default;
}
static IssueFilter MakeIssueFilter(CriteriaOperator filter) {
    return null;
}

VirtualSourceTutorialScrolling

The FetchRowsEventArgsBase.Take property returns the number of rows that should be reloaded. Use this property to allow the InfiniteAsyncSource to retain a selected row and scroll position after refresh. The PagedAsyncSource automatically retains a selected row and scroll position.

If data in your source are changed frequently, you can retain the same selected row after refresh. Specify the VirtualSourceBase.KeyProperty property to make a virtual source find the selected row by a specific field.

If you want to maintain a clean MVVM pattern and specify a fetch operation in a ViewModel, create a command and bind it to the InfiniteAsyncSource.FetchRowsCommand property.

See Also