Step 4: Display Summaries

• Dec 26, 2018

In this step, you display total summaries in the GridControl bound to a virtual source.

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 DevExpress.Data.InfiniteAsyncSource.GetTotalSummaries event.
   • Get summaries from the data source using the Issues Service’s GetSummariesAsync method.
   • Get the GridControl‘s summary items using the DevExpress.Data.GetSummariesEventArgsBase.Summaries property.
   • Return summaries that correspond to the GridControl‘s summary items by specifying the DevExpress.Data.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 DataControlBase.ShowFixedTotalSummary property to true to show the Fixed Summary Panel:

   XAML

       <Grid:GridControl Name="grid" AutoGenerateColumns="False" AllowSorting="False" AllowColumnFiltering="False"
                         ShowFixedTotalSummary="True">
   

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

   XAML

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