How to speed up a WPF DataGrid bound to an ObservableCollection?

Richard Haggard 6 Reputation points
2020-06-17T15:26:34.737+00:00

The application is WPF/MVVM. A DataGrid's ItemSource is bound to an ObservableCollection<LogItem> where LogItem is a plain class of 5 strings and one enumerated value, none of which support the INotifyPropertyChanged interface. The problem is that the time between when the ObservableCollection is updated and when the DataGrid actually displays anything seems excessively long and I'm hoping there's some way to speed this up.

Here's what I mean. There is a button whose command causes a UserControl to get created. In the UC's associated ViewModel class constructor the ObservableCollection is populated with about 1600 items. The actual population is quick but the UI thread stalls for about 15 seconds which is unexpectedly long. What I suspect is happening is that the DataGrid itself is handling a boat load of notifications from the ObservableCollection and due to sorting and what not it just takes a while.

On the other hand, I've been using DataGrids for years and haven't ever seen anything this poor in performance before but normally I use a DataTable instead of an ObservableCollection.

Windows Presentation Foundation
Windows Presentation Foundation
A part of the .NET Framework that provides a unified programming model for building line-of-business desktop applications on Windows.
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  1. Peter Fleischer (former MVP) 19,311 Reputation points
    2020-06-18T06:01:23.957+00:00

    Hi, without knowing your code, it is impossible to investigate your problem. The following small demo shows that the 1600 data rows with 6 columns are displayed very quickly. They are not loaded in the constructor, but only when the DataGrid in the UserControl only fetches the data for display. 

    <Window x:Class="Window032"
        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:WpfApp1.WpfApp032"
        xmlns:uc="clr-namespace:WpfControlLibrary1;assembly=WpfControlLibrary1"
        mc:Ignorable="d"
        Title="Window032" Height="450" Width="800">
  <Window.DataContext>
    <local:ViewModel/>
  </Window.DataContext>
  <Grid>
    <uc:Window032UC1/>
  </Grid>
</Window>

    Imports System.Collections.ObjectModel
Imports System.ComponentModel

Namespace WpfApp032
  Public Class ViewModel
    Public ReadOnly Property View As ICollectionView
      Get
        If cvs.Source Is Nothing Then
          getData()
          cvs.Source = col
        End If
        Return cvs.View
      End Get
    End Property

    Private cvs As New CollectionViewSource
    Private col As ObservableCollection(Of LogItem)

    Private Sub getData()
      col = New ObservableCollection(Of LogItem)
      For i = 1 To 1600
        col.Add(New LogItem With {.ID = i, .String1 = $"String1: {i}", .String2 = $"String2: {i}", .String3 = $"String3: {i}", .String4 = $"String4: {i}", .String5 = $"String5: {i}"})
      Next
    End Sub
  End Class

  Public Class LogItem
    Public Property ID As Integer
    Public Property String1 As String
    Public Property String2 As String
    Public Property String3 As String
    Public Property String4 As String
    Public Property String5 As String
  End Class

End Namespace

    <UserControl x:Class="Window032UC1"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             xmlns:local="clr-namespace:WpfControlLibrary1"
             mc:Ignorable="d" 
             d:DesignHeight="450" d:DesignWidth="800">
  <Grid>
    <DataGrid ItemsSource="{Binding View}"/>
  </Grid>
</UserControl>
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