Step 1: Fetch Data and Enable Scrolling

• Oct 08, 2018
• 2 minutes to read

In this step, you create a virtual source, fetch rows from the service, and enable scrolling in the GridControl.

To Fetch Data and Enable Scrolling

1. Add a GridControl with columns that correspond to the Issues Service’s IssueData to your project:

   XAML

       <Grid:GridControl Name="grid" AutoGenerateColumns="False" AllowSorting="False" AllowColumnFiltering="False">
           <Grid:GridControl.Columns>
               <Grid:GridTextColumn FieldName="Subject" />
               <Grid:GridTextColumn FieldName="User" />
               <Grid:GridDateColumn FieldName="Created" />
               <Grid:GridTextColumn FieldName="Votes"  />
               <Grid:GridTextColumn FieldName="Priority" />
           </Grid:GridControl.Columns>
       </Grid:GridControl>
   

2. Initialize a virtual source. Create an InfiniteAsyncSource instance and set the VirtualSourceBase.ElementType property to the type of rows retrieved from the source.

   C#

       public MainPage() {
           this.InitializeComponent();
           var source = new InfiniteAsyncSource() {
               ElementType = typeof(IssueData)
           };
       }
   

Tip

If your service returns untyped objects (for example, a service returns Json which is converted to a dynamic object), specify the VirtualSourceBase.CustomProperties property.

3. Fetch rows from the data source:

   • Handle the InfiniteAsyncSource.FetchRows event.
   • Obtain data using the Issues Service’s GetIssuesAsync method.
   • Create the FetchRowsResult class object and specify the FetchRowsAsyncEventArgs.Result property.
   C#

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

4. Bind the GridControl to the virtual source by assigning the resulting virtual source’s instance to the DataControlBase.ItemsSource property:

   C#

   public MainPage() {
       // ... 
       grid.ItemsSource = source;
   }