Step 4: Display Summaries

• Jun 20, 2018
• 2 minutes to read

You should enable data operations after binding the GridControl to a virtual source.

In this step, we describe how to display summaries:

• You process summaries in the virtual source.
• Then you display summaries in the GridControl.

Note

The Issues Service is used as an example of a data source in this tutorial.

Overview

The Issues Service can get:

• A 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; }
}

To Display Summaries

1. Process summaries in the virtual source:

   • Handle the InfiniteAsyncSource.GetTotalSummaries event.
   • Get summaries from the data source using the Issues Service‘s GetSummariesAsync method.
   • Get the GridControl‘s summary items using the GetSummariesEventArgsBase.Summaries property.
   • Return summaries that correspond to the GridControl‘s summary items by specifying the GetSummariesAsyncEventArgs.Result property.
   C#

   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 DataViewBase.ShowFixedTotalSummary property to true to show the Fixed Summary Panel:

   XAML

   <dxg:TableView ShowFixedTotalSummary="True" />
   

3. Display total summaries in the GridControl by specifying the GridControl.TotalSummary property:

   XAML

   <dxg:GridControl.TotalSummary>
       <dxg:GridSummaryItem SummaryType="Count" Alignment="Right"/>
       <dxg:GridSummaryItem SummaryType="Max" FieldName="Created" DisplayFormat="{}Last created: {0}" Alignment="Right"/>
   </dxg:GridControl.TotalSummary>
   

To Continue or Review

• To go to the next tutorial, see How to Bind to a Custom Service with Restrictions.
• To return to the previous tutorial step, see Step 3: Enable Filtering.