InfiniteAsyncSource.FetchRows Event

Allows you to fetch rows.

Namespace: DevExpress.Xpf.Data

Assembly: DevExpress.Xpf.Core.v20.1.dll

Declaration

public event EventHandler<FetchRowsAsyncEventArgs> FetchRows
Public Event FetchRows As EventHandler(Of FetchRowsAsyncEventArgs)

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 one of the following values: * null when the grid fetches next portion of data (a user scrolls rows). * the number of rows within and above the viewport that are reloaded when you call the RefreshRows method or users press F5. * int.Max when you call the InfiniteAsyncSource.ReloadRows / PagedAsyncSource.ReloadRows method. Inherited from FetchRowsEventArgsBase.

Remarks

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.

See Also