Other Virtual Sources

• Jan 28, 2022
• 2 minutes to read

The How to Use Virtual Sources tutorial demonstrates how to bind to InfiniteAsyncSource. This topic describes other virtual sources’ specificities.

Paged Sources

This section describes how to use the PagedAsyncSource or PagedSource.

Important

The PagedSource is obsolete. Use the PagedAsyncSource instead.

Examples

• How to Bind to PagedAsyncSource
• How to Bind to PagedSource

Specificities

• You can specify the PagedSourceBase.PageSize property to set the maximum number of rows that can be displayed on a page.
• You can set the PagedSourceBase.PageNavigationMode property to Arbitrary to allow navigating to any page.

• To show a total page count:

  1. Set the PagedSourceBase.PageNavigationMode property to ArbitraryWithTotalPageCount.
  2. Handle the PagedAsyncSource.GetTotalSummaries (or PagedSource.GetTotalSummaries) event to calculate the Count value.
• Use the PagedAsyncSource.FetchPage (or PagedSource.FetchPage) event to fetch a page.

InfiniteSource / PagedSource

This section describes how to use the InfiniteSource or PagedSource.

Important

The InfiniteSource and PagedSource are obsolete. Use the InfiniteAsyncSource and PagedAsyncSource instead.

Examples

In the examples below, a data access object (IssuesContext) emulation is used instead of a web service emulation:

• How to Bind to InfiniteSource
• How to Bind to PagedSource

Specificities:

• In addition to the InfiniteSource.FetchRows and PagedSource.FetchPage events, you have to handle the InfiniteSource.CreateSource (or PagedSource.CreateSource) and InfiniteSource.DisposeSource (or PagedSource.DisposeSource) events:

  C#

  source.CreateSource += (o, e) => {
      e.Source = new IssuesContext();
  };
  source.DisposeSource += (o, e) => {
      var issuesContext = (IssuesContext)e.Source;
      issuesContext.Dispose();
  };
  

• Get the IssuesContext before obtaining rows:

  C#

  static FetchRowsResult FetchRows(FetchRowsEventArgs e) {
      // ...
      var issuesContext = (IssuesContext)e.Source;            
      var issues = issuesContext.GetIssues(
          page: e.Skip / pageSize, 
          pageSize: pageSize, 
          sortOrder: sortOrder, 
          filter: filter);
      // ...
  }
  static object[] GetTotalSummaries(GetSummariesEventArgs e) {
      // ...
      var issuesContext = (IssuesContext)e.Source;
      var summaryValues = issuesContext.GetSummaries(filter);
      // ...
  }
  

• In the InfiniteSource.FetchRows (or PagedSource.FetchPage) handler, return a list of objects separately and specify the FetchRowsEventArgs.HasMoreRows (or FetchPageEventArgs.HasMoreRows) property:

  C#

  source.FetchRows += (o, e) => {
      var fetchRowsResult = FetchRows(e);
      e.Result = fetchRowsResult.Rows;
      e.HasMoreRows = fetchRowsResult.HasMoreRows;
  };