Step 2: Enable Sorting

• Dec 26, 2018
• 2 minutes to read

In this step, you enable the sorting functionality in the GridControl bound to a virtual source.

Overview

The Issues Service allows you to apply the following sort orders:

• Default - records are shown from new to old
• Created Date in Descending order

• Votes in any order

  C#

  public enum IssueSortOrder {
      Default,
      CreatedDescending,
      VotesAscending,
      VotesDescending
  }
  

  In Step 1: Fetch Data and Enable Scrolling, you have fetched rows with the default sort order:

  C#

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

To Enable Sorting

1. Implement sorting in the virtual source:

   • Get the GridControl‘s sorting using the DevExpress.Data.FetchEventArgsBase.SortOrder property.
   • Parse sorting and return a sort order. The DevExpress.Data.InfiniteAsyncSource.FetchRows event handler takes into account this sort order when fetching rows.
   C#

       static IssueSortOrder GetIssueSortOrder(FetchRowsAsyncEventArgs e) {
           IssueSortOrder sortOrder = IssueSortOrder.Default;
           if (e.SortOrder.Length > 0) {
               var sort = e.SortOrder.Single();
               if (sort.PropertyName == "Created") {
                   if (sort.Direction != ListSortDirection.Descending)
                       throw new InvalidOperationException();
                   sortOrder = IssueSortOrder.CreatedDescending;
               }
               if (sort.PropertyName == "Votes") {
                   sortOrder = sort.Direction == ListSortDirection.Ascending
                       ? IssueSortOrder.VotesAscending
                       : IssueSortOrder.VotesDescending;
               }
           }
           return sortOrder;
       }
   

2. Allow sorting in the GridControl by the Votes and Created column’s values. Set the ColumnBase.AllowSorting property to true for these columns.

   XAML

               <Grid:GridDateColumn FieldName="Created" AllowSorting="True" />
               <Grid:GridTextColumn FieldName="Votes" AllowSorting="True" />