PivotGridControl.CustomSummary Event

<dx:ThemedWindow x:Class="DXPivotGrid_CustomSummary.MainWindow" mc:Ignorable="d" Title="MainWindow" Height="450" Width="800" 
    xmlns:dx="http://schemas.devexpress.com/winfx/2008/xaml/core" 
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
    xmlns:local="clr-namespace:DXPivotGrid_CustomSummary" 
    xmlns:dxpg="http://schemas.devexpress.com/winfx/2008/xaml/pivotgrid">
    <Grid>

        <dxpg:PivotGridControl CustomSummary="pivotGridControl1_CustomSummary" Loaded="PivotGridControl1_Loaded" Name="pivotGridControl1">
            <dxpg:PivotGridControl.Fields>
                <dxpg:PivotGridField Name="fieldCategoryName" FieldName="CategoryName" Area="RowArea" AreaIndex="0" Caption="Category Name" />
                <dxpg:PivotGridField Name="fieldProductName" FieldName="ProductName" Area="RowArea" AreaIndex="1" Caption="Product Name" />
                <dxpg:PivotGridField Name="fieldOrderDate" FieldName="OrderDate" Area="ColumnArea" AreaIndex="0" Caption="OrderDate" GroupInterval="DateYear" />
                <dxpg:PivotGridField Name="fieldQuantity" FieldName="Quantity" Area="DataArea" AreaIndex="0" Caption="Quantity" />
                <dxpg:PivotGridField Name="fieldQuantityDistinctCount" FieldName="Quantity" Area="DataArea" AreaIndex="1" Caption="Count Distinct" SummaryType="Custom" />
            </dxpg:PivotGridControl.Fields>
        </dxpg:PivotGridControl>

    </Grid>
</dx:ThemedWindow>

Imports DevExpress.DataAccess.Excel
Imports System
Imports System.Collections
Imports System.Windows

Namespace DXPivotGrid_CustomSummary
  ''' <summary>
  ''' Interaction logic for MainWindow.xaml
  ''' </summary>
  Partial Public Class MainWindow
    Inherits DevExpress.Xpf.Core.ThemedWindow

    Private ds As New ExcelDataSource()
    Public Sub New()
      InitializeComponent()

      ds.Name = "Excel Data Source" 
      ds.FileName = "SalesPerson.xlsx" 
      Dim worksheetSettings As New ExcelWorksheetSettings("Data")
      ds.SourceOptions = New ExcelSourceOptions(worksheetSettings)
      ds.Fill()

      pivotGridControl1.DataSource = ds
    End Sub

    Private Sub pivotGridControl1_CustomSummary(ByVal sender As Object, ByVal e As DevExpress.Xpf.PivotGrid.PivotCustomSummaryEventArgs)
      Dim name_Renamed As String = e.DataField.FieldName

      Dim list As IList = e.CreateDrillDownDataSource()
      Dim ht As New Hashtable()
      For i As Integer = 0 To list.Count - 1
        Dim row As DevExpress.XtraPivotGrid.PivotDrillDownDataRow = TryCast(list(i), DevExpress.XtraPivotGrid.PivotDrillDownDataRow)
        Dim v As Object = row(name_Renamed)
        If v IsNot Nothing AndAlso v IsNot DBNull.Value Then
          ht(v) = Nothing
        End If
      Next i
      e.CustomValue = ht.Count
    End Sub

    Private Sub PivotGridControl1_Loaded(ByVal sender As Object, ByVal e As RoutedEventArgs)
      pivotGridControl1.BestFit()
    End Sub
  End Class
End Namespace

using DevExpress.DataAccess.Excel;
using System;
using System.Collections;
using System.Windows;

namespace DXPivotGrid_CustomSummary
{
    /// <summary> 
    /// Interaction logic for MainWindow.xaml 
    /// </summary> 
    public partial class MainWindow : DevExpress.Xpf.Core.ThemedWindow
    {
        ExcelDataSource ds = new ExcelDataSource();
        public MainWindow()
        {
            InitializeComponent();

            ds.Name = "Excel Data Source";
            ds.FileName = "SalesPerson.xlsx";
            ExcelWorksheetSettings worksheetSettings = new ExcelWorksheetSettings("Data");
            ds.SourceOptions = new ExcelSourceOptions(worksheetSettings);
            ds.Fill();

            pivotGridControl1.DataSource = ds;
        }

        private void pivotGridControl1_CustomSummary(object sender, DevExpress.Xpf.PivotGrid.PivotCustomSummaryEventArgs e)
        {
            string name = e.DataField.FieldName;

            IList list = e.CreateDrillDownDataSource();
            Hashtable ht = new Hashtable();
            for (int i = 0; i < list.Count; i++)
            {
                DevExpress.XtraPivotGrid.PivotDrillDownDataRow row = list[i] as DevExpress.XtraPivotGrid.PivotDrillDownDataRow;
                object v = row[name];
                if (v != null && v != DBNull.Value)
                    ht[v] = null;
            }
            e.CustomValue = ht.Count;
        }

        private void PivotGridControl1_Loaded(object sender, RoutedEventArgs e)
        {
            pivotGridControl1.BestFit();
        }
    }
}