Step 4: Display Summaries

• Aug 17, 2022
• 2 minutes to read

This step describes how to display summaries:

• Process summaries in the virtual source.
• Display summaries in the GridControl.

View Example: Data Grid - Bind to InfiniteAsyncSource

Summary Types

The Issues Service allows you to obtain:

• The total count of rows.
• The last created object’s datetime.

C#

public class IssuesSummaries {   
    public int Count { get; private set; }
    public DateTime? LastCreated { get; private set; }
}

Display Summaries

1. Process summaries in the virtual source:

   • Create a task that uses the Issues Service’s GetSummariesAsync method to get summaries from the data source.
   • Use the Summaries property to get the GridControl‘s summary items.
   • Handle the InfiniteAsyncSource.GetTotalSummaries event.
   • Get a list of data source summaries that correspond to the GridControl‘s summary items. Assign the list to the Result property.
   C#

   public MainPage() {
       // ...
   
       source.GetTotalSummaries += (o, e) => {
           e.Result = GetTotalSummariesAsync(e);
       };
   }
   
   static async Task<object[]> GetTotalSummariesAsync(GetSummariesAsyncEventArgs e) {
       IssueFilter filter = MakeIssueFilter(e.Filter);
       var summaryValues = await IssuesService.GetSummariesAsync(filter);
       return e.Summaries.Select(x => {
           if (x.SummaryType == SummaryType.Count)
               return (object)summaryValues.Count;
           if (x.SummaryType == SummaryType.Max && x.PropertyName == "Created")
               return summaryValues.LastCreated;
           throw new InvalidOperationException();
       }).ToArray();
   }
   

2. Set the DataControlBase.ShowFixedTotalSummary property to true to show the Fixed Summary Panel. You can also use the DataControlBase.ShowTotalSummary property to display the Summary Panel.

   XAML

   <dxg:GridControl ... 
                    ShowFixedTotalSummary="True">
       <!-- ... -->
   </dxg:GridControl>
   

3. Specify the GridControl.TotalSummary property to display total summaries in the GridControl:

   XAML

   <dxg:GridControl.TotalSummary>
       <dxg:GridTotalSummaryItem SummaryType="Count" Alignment="Right"/>
       <dxg:GridTotalSummaryItem SummaryType="Max" FieldName="Created" 
                                 Caption="Last created:" Alignment="Right"/>
   </dxg:GridControl.TotalSummary>
   

Continue or Review

• Proceed to Virtual Sources Limitations.
• Review Step 3 - Enable Filter Operations.